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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.08211">arXiv:2411.08211</a> <span> [<a href="https://arxiv.org/pdf/2411.08211">pdf</a>, <a href="https://arxiv.org/format/2411.08211">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> </div> <p class="title is-5 mathjax"> Detection asymmetry in solar energetic particle events </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Dalla%2C+S">S. Dalla</a>, <a href="/search/astro-ph?searchtype=author&query=Hutchinson%2C+A">A. Hutchinson</a>, <a href="/search/astro-ph?searchtype=author&query=Hyndman%2C+R+A">R. A. Hyndman</a>, <a href="/search/astro-ph?searchtype=author&query=Kihara%2C+K">K. Kihara</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">N. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Rodriguez-Garcia%2C+L">L. Rodriguez-Garcia</a>, <a href="/search/astro-ph?searchtype=author&query=Laitinen%2C+T">T. Laitinen</a>, <a href="/search/astro-ph?searchtype=author&query=Waterfall%2C+C+O+G">C. O. G. Waterfall</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+D+S">D. S. Brown</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.08211v3-abstract-short" style="display: inline;"> Context. Solar energetic particles (SEPs) are detected in interplanetary space in association with solar flares and coronal mass ejections (CMEs). The magnetic connection between the observing spacecraft and the solar active region (AR) source of the event is a key parameter in determining whether SEPs are observed and the particle event's properties. Aims. We investigate whether an east-west asym… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.08211v3-abstract-full').style.display = 'inline'; document.getElementById('2411.08211v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.08211v3-abstract-full" style="display: none;"> Context. Solar energetic particles (SEPs) are detected in interplanetary space in association with solar flares and coronal mass ejections (CMEs). The magnetic connection between the observing spacecraft and the solar active region (AR) source of the event is a key parameter in determining whether SEPs are observed and the particle event's properties. Aims. We investigate whether an east-west asymmetry in the detection of SEP events is present in observations and discuss its possible link to corotation of magnetic flux tubes with the Sun. Methods. We used a published dataset of 239 CMEs recorded between 2006 and 2017 and having source regions both on the Sun's front and far sides as seen from Earth. We produced distributions of occurrence of in-situ SEP intensity enhancements associated with the CME events, versus 螖蠁, the longitudinal separation between source active region and spacecraft magnetic footpoint based on the nominal Parker spiral. We focused on protons of energy >10 MeV measured by STEREO A, STEREO B and GOES at 1 au. We also considered occurrences of 71-112 keV electron events detected by MESSENGER between 0.31 and 0.47 au. Results. We find an east-west asymmetry with respect to the best magnetic connection (螖蠁=0) in the detection of >10 MeV proton events and of 71-112 keV electron events. For protons, observers for which the source AR is on the east side of the spacecraft footpoint and not well connected (-180<螖蠁<-40) are 93% more likely to detect an SEP event compared to observers with +40<螖蠁<+180. The asymmetry may be a signature of corotation of magnetic flux tubes with the Sun, since for events with 螖蠁<0 corotation sweeps particle-filled flux tubes towards the observing spacecraft, while for 螖蠁>0 it takes them away from it. Alternatively it may be related to asymmetric acceleration or propagation effects. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.08211v3-abstract-full').style.display = 'none'; document.getElementById('2411.08211v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">A&A, in press</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2409.18020">arXiv:2409.18020</a> <span> [<a href="https://arxiv.org/pdf/2409.18020">pdf</a>, <a href="https://arxiv.org/format/2409.18020">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> Exploring the Dynamics of CME-Driven Shocks by Comparing Numerical Modeling and Observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Jin%2C+M">Meng Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Li%2C+G">Gang Li</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+W">Wei Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Petrosian%2C+V">Vahe Petrosian</a>, <a href="/search/astro-ph?searchtype=author&query=Manchester%2C+W">Ward Manchester</a>, <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+C">Christina Cohen</a>, <a href="/search/astro-ph?searchtype=author&query=Effenberger%2C+F">Frederic Effenberger</a>, <a href="/search/astro-ph?searchtype=author&query=Ding%2C+Z">Zheyi Ding</a>, <a href="/search/astro-ph?searchtype=author&query=Pesce-Rollins%2C+M">Melissa Pesce-Rollins</a>, <a href="/search/astro-ph?searchtype=author&query=Omodei%2C+N">Nicola Omodei</a>, <a href="/search/astro-ph?searchtype=author&query=Gopalswamy%2C+N">Nat Gopalswamy</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2409.18020v1-abstract-short" style="display: inline;"> Shocks driven by coronal mass ejections (CMEs) are primary drivers of gradual solar energetic particle (SEP) events, posing significant risks to space technology and astronauts. Concurrently, particles accelerated at these shocks may also propagate back to the Sun, potentially generating gamma-ray emissions through pion decay. We incorporated advanced modeling and multi-messenger observations to e… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.18020v1-abstract-full').style.display = 'inline'; document.getElementById('2409.18020v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2409.18020v1-abstract-full" style="display: none;"> Shocks driven by coronal mass ejections (CMEs) are primary drivers of gradual solar energetic particle (SEP) events, posing significant risks to space technology and astronauts. Concurrently, particles accelerated at these shocks may also propagate back to the Sun, potentially generating gamma-ray emissions through pion decay. We incorporated advanced modeling and multi-messenger observations to explore the role of CME-driven shocks in gamma-ray emissions and SEPs. Motivated by Fermi-LAT long-duration solar flares, we used the AWSoM MHD model to investigate the connection between the shocks and the properties of observed gamma-ray emissions. By coupling the AWSoM with iPATH model, we evaluate the impact of shock evolution complexity near the Sun on SEP intensity and spectra. Our result points to the importance of accurate background coronal and solar wind modeling, as well as detailed observations of CME source regions, in advancing our understanding of CME-driven shocks and the dynamics of associated energetic particles. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.18020v1-abstract-full').style.display = 'none'; document.getElementById('2409.18020v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 6 figures, to appear in the Proceedings of IAU Symposium No. 388 - Solar and Stellar Coronal Mass Ejections</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.00924">arXiv:2305.00924</a> <span> [<a href="https://arxiv.org/pdf/2305.00924">pdf</a>, <a href="https://arxiv.org/format/2305.00924">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/acd178">10.3847/1538-4357/acd178 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Limitations and biases in the retrieval of the polar magnetic field I: the role of the magnetic filling factor in Milne-Eddington inversions of simulated Hinode/SP data </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Centeno%2C+R">Rebecca Centeno</a>, <a href="/search/astro-ph?searchtype=author&query=Mili%C4%87%2C+I">Ivan Mili膰</a>, <a href="/search/astro-ph?searchtype=author&query=Rempel%2C+M">Matthias Rempel</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Sun%2C+X">Xudong Sun</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2305.00924v1-abstract-short" style="display: inline;"> We study the extent to which Milne-Eddington inversions are able to retrieve and characterize the magnetic landscape of the solar poles from observations by the spectropolarimeter onboard Hinode. In particular, we evaluate whether a variable magnetic filling factor is an adequate modeling technique for retrieving the intrinsic magnetic properties from every pixel in the polar field of view. We fir… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.00924v1-abstract-full').style.display = 'inline'; document.getElementById('2305.00924v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.00924v1-abstract-full" style="display: none;"> We study the extent to which Milne-Eddington inversions are able to retrieve and characterize the magnetic landscape of the solar poles from observations by the spectropolarimeter onboard Hinode. In particular, we evaluate whether a variable magnetic filling factor is an adequate modeling technique for retrieving the intrinsic magnetic properties from every pixel in the polar field of view. We first generate synthetic spectra emerging from a numerical simulation of a "plage" region at an inclined line of sight of 65$^{\circ}$, and degrade the data to emulate real observations. Then, we invert the synthetic spectra with two Milne-Eddington inversion codes that feature different treatments of the magnetic filling factor, and relate the retrieved magnetic quantities back to their original values in the simulation cube. We find that while the apparent retrieved magnetic properties map well the spatially-degraded simulation, the intrinsic magnetic quantities bear little relation to the magnetic field at the native resolution of the simulation. We discuss the systematic biases caused by line-of-sight foreshortening, spatial degradation, photon noise and modeling assumptions embedded in the inversion algorithm. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.00924v1-abstract-full').style.display = 'none'; document.getElementById('2305.00924v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.13541">arXiv:2302.13541</a> <span> [<a href="https://arxiv.org/pdf/2302.13541">pdf</a>, <a href="https://arxiv.org/format/2302.13541">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/acbea3">10.3847/1538-4357/acbea3 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Solar Energetic Particle Events with Short and Long Onset Times </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kihara%2C+K">Kosuke Kihara</a>, <a href="/search/astro-ph?searchtype=author&query=Asai%2C+A">Ayumi Asai</a>, <a href="/search/astro-ph?searchtype=author&query=Yashiro%2C+S">Seiji Yashiro</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2302.13541v1-abstract-short" style="display: inline;"> Gradual solar energetic particle (SEP) events, usually attributed to shock waves driven by coronal mass ejections (CMEs), show a wide variety of temporal behaviors. For example, TO, the >10 MeV proton onset time with respect to the launch of the CME, has a distribution of at least an order of magnitude, even when the source region is not far from the so-called well-connected longitudes. It is impo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.13541v1-abstract-full').style.display = 'inline'; document.getElementById('2302.13541v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.13541v1-abstract-full" style="display: none;"> Gradual solar energetic particle (SEP) events, usually attributed to shock waves driven by coronal mass ejections (CMEs), show a wide variety of temporal behaviors. For example, TO, the >10 MeV proton onset time with respect to the launch of the CME, has a distribution of at least an order of magnitude, even when the source region is not far from the so-called well-connected longitudes. It is important to understand what controls TO, especially in the context of space weather prediction. Here we study two SEP events from the western hemisphere that are different in TO on the basis of >10 MeV proton data from the Geostationary Operations Environmental Satellite, despite similar in the CME speed and longitude of the source regions. We try to find the reasons for different TO, or proton release times, in how the CME-driven shock develops and the Alfv茅n Mach number of the shock wave reaches some threshold, by combining the CME height-time profiles with radio dynamic spectra. We also discuss how CME-CME interactions and active region properties may affect proton release times. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.13541v1-abstract-full').style.display = 'none'; document.getElementById('2302.13541v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 8 figures, accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.12825">arXiv:2211.12825</a> <span> [<a href="https://arxiv.org/pdf/2211.12825">pdf</a>, <a href="https://arxiv.org/format/2211.12825">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/aca52c">10.3847/1538-4357/aca52c <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Is there a Dynamic Difference between Stealthy and Standard CMEs? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ying%2C+B">Beili Ying</a>, <a href="/search/astro-ph?searchtype=author&query=Bemporad%2C+A">Alessandro Bemporad</a>, <a href="/search/astro-ph?searchtype=author&query=Feng%2C+L">Li Feng</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Gan%2C+W">Weiqun Gan</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2211.12825v1-abstract-short" style="display: inline;"> Stealthy Coronal Mass Ejections (CMEs), lacking low coronal signatures, may result in significant geomagnetic storms. However, the mechanism of stealthy CMEs is still highly debated. In this work, we investigate whether there are differences between the stealthy and standard CMEs in terms of their dynamic behaviors. Seven stealthy and eight standard CMEs with slow speeds are selected. We calculate… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.12825v1-abstract-full').style.display = 'inline'; document.getElementById('2211.12825v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.12825v1-abstract-full" style="display: none;"> Stealthy Coronal Mass Ejections (CMEs), lacking low coronal signatures, may result in significant geomagnetic storms. However, the mechanism of stealthy CMEs is still highly debated. In this work, we investigate whether there are differences between the stealthy and standard CMEs in terms of their dynamic behaviors. Seven stealthy and eight standard CMEs with slow speeds are selected. We calculate two-dimensional speed distributions of CMEs based on the cross-correlation method, rather than the unidimensional speed, and further obtain more accurate distributions and evolution of CME mechanical energies. Then we derive the CME driving powers and correlate them with CME parameters (total mass, average speed, and acceleration) for standard and stealthy CMEs. Besides, we study the forces that drive CMEs, namely, the Lorentz force, gravitational force, and drag force due to the ambient solar wind near the Sun. The results reveal that both the standard and stealthy CMEs are propelled by the combined action of those forces in the inner corona. The drag force and gravitational force are comparable with the Lorentz force. However, the impact of the drag and Lorentz forces on the global evolution of the stealthy CMEs is significantly weaker than that of the standard CMEs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.12825v1-abstract-full').style.display = 'none'; document.getElementById('2211.12825v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 7 figures, 1 table. Accepted by ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.16403">arXiv:2210.16403</a> <span> [<a href="https://arxiv.org/pdf/2210.16403">pdf</a>, <a href="https://arxiv.org/ps/2210.16403">ps</a>, <a href="https://arxiv.org/format/2210.16403">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202245037">10.1051/0004-6361/202245037 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The first gradual solar energetic particle event with enhanced 3He abundance on Solar Orbiter </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bu%C4%8D%C3%ADk%2C+R">R. Bu膷铆k</a>, <a href="/search/astro-ph?searchtype=author&query=Mason%2C+G+M">G. M. Mason</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez-Herrero%2C+R">R. G贸mez-Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Krupar%2C+V">V. Krupar</a>, <a href="/search/astro-ph?searchtype=author&query=Lario%2C+D">D. Lario</a>, <a href="/search/astro-ph?searchtype=author&query=Starkey%2C+M+J">M. J. Starkey</a>, <a href="/search/astro-ph?searchtype=author&query=Ho%2C+G+C">G. C. Ho</a>, <a href="/search/astro-ph?searchtype=author&query=Rodr%C3%ADguez-Pacheco%2C+J">J. Rodr铆guez-Pacheco</a>, <a href="/search/astro-ph?searchtype=author&query=Wimmer-Schweingruber%2C+R+F">R. F. Wimmer-Schweingruber</a>, <a href="/search/astro-ph?searchtype=author&query=Lara%2C+F+E">F. Espinosa Lara</a>, <a href="/search/astro-ph?searchtype=author&query=Tadesse%2C+T">T. Tadesse</a>, <a href="/search/astro-ph?searchtype=author&query=Balmaceda%2C+L">L. Balmaceda</a>, <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+C+M+S">C. M. S. Cohen</a>, <a href="/search/astro-ph?searchtype=author&query=Dayeh%2C+M+A">M. A. Dayeh</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+M+I">M. I. Desai</a>, <a href="/search/astro-ph?searchtype=author&query=K%C3%BChl%2C+P">P. K眉hl</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Wiedenbeck%2C+M+E">M. E. Wiedenbeck</a>, <a href="/search/astro-ph?searchtype=author&query=Xu%2C+Z+G">Z. G. Xu</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2210.16403v1-abstract-short" style="display: inline;"> The origin of 3He abundance enhancements in coronal mass ejection (CME)-driven shock gradual solar energetic particle (SEP) events remains largely unexplained. Two mechanisms have been suggested - the re-acceleration of remnant flare material in interplanetary space and concomitant activity in the corona. We explore the first gradual SEP event with enhanced 3He abundance observed by Solar Orbiter.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.16403v1-abstract-full').style.display = 'inline'; document.getElementById('2210.16403v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.16403v1-abstract-full" style="display: none;"> The origin of 3He abundance enhancements in coronal mass ejection (CME)-driven shock gradual solar energetic particle (SEP) events remains largely unexplained. Two mechanisms have been suggested - the re-acceleration of remnant flare material in interplanetary space and concomitant activity in the corona. We explore the first gradual SEP event with enhanced 3He abundance observed by Solar Orbiter. The event started on 2020 November 24 and was associated with a relatively fast halo CME. During the event, the spacecraft was at 0.9 au from the Sun. The event averaged 3He/4He abundance ratio is 24 times higher than the coronal or solar wind value, and the 3He intensity had timing similar to other species. We inspected available imaging, radio observations, and spacecraft magnetic connection to the CME source. It appears the most probable cause of the enhanced 3He abundance are residual 3He ions remaining from a preceding long period of 3He-rich SEPs on 2020 November 17-23. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.16403v1-abstract-full').style.display = 'none'; document.getElementById('2210.16403v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 9 figures, accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 669, A13 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.05760">arXiv:2209.05760</a> <span> [<a href="https://arxiv.org/pdf/2209.05760">pdf</a>, <a href="https://arxiv.org/format/2209.05760">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1029/2022SW003215">10.1029/2022SW003215 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> CME Evolution in the Structured Heliosphere and Effects at Earth and Mars During Solar Minimum </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Palmerio%2C+E">Erika Palmerio</a>, <a href="/search/astro-ph?searchtype=author&query=Lee%2C+C+O">Christina O. Lee</a>, <a href="/search/astro-ph?searchtype=author&query=Richardson%2C+I+G">Ian G. Richardson</a>, <a href="/search/astro-ph?searchtype=author&query=Nieves-Chinchilla%2C+T">Teresa Nieves-Chinchilla</a>, <a href="/search/astro-ph?searchtype=author&query=Santos%2C+L+F+G+D">Luiz F. G. Dos Santos</a>, <a href="/search/astro-ph?searchtype=author&query=Gruesbeck%2C+J+R">Jacob R. Gruesbeck</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Mays%2C+M+L">M. Leila Mays</a>, <a href="/search/astro-ph?searchtype=author&query=Halekas%2C+J+S">Jasper S. Halekas</a>, <a href="/search/astro-ph?searchtype=author&query=Zeitlin%2C+C">Cary Zeitlin</a>, <a href="/search/astro-ph?searchtype=author&query=Xu%2C+S">Shaosui Xu</a>, <a href="/search/astro-ph?searchtype=author&query=Holmstr%C3%B6m%2C+M">Mats Holmstr枚m</a>, <a href="/search/astro-ph?searchtype=author&query=Futaana%2C+Y">Yoshifumi Futaana</a>, <a href="/search/astro-ph?searchtype=author&query=Mulligan%2C+T">Tamitha Mulligan</a>, <a href="/search/astro-ph?searchtype=author&query=Lynch%2C+B+J">Benjamin J. Lynch</a>, <a href="/search/astro-ph?searchtype=author&query=Luhmann%2C+J+G">Janet G. Luhmann</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2209.05760v1-abstract-short" style="display: inline;"> The activity of the Sun alternates between a solar minimum and a solar maximum, the former corresponding to a period of "quieter" status of the heliosphere. During solar minimum, it is in principle more straightforward to follow eruptive events and solar wind structures from their birth at the Sun throughout their interplanetary journey. In this paper, we report analysis of the origin, evolution,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.05760v1-abstract-full').style.display = 'inline'; document.getElementById('2209.05760v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.05760v1-abstract-full" style="display: none;"> The activity of the Sun alternates between a solar minimum and a solar maximum, the former corresponding to a period of "quieter" status of the heliosphere. During solar minimum, it is in principle more straightforward to follow eruptive events and solar wind structures from their birth at the Sun throughout their interplanetary journey. In this paper, we report analysis of the origin, evolution, and heliospheric impact of a series of solar transient events that took place during the second half of August 2018, i.e. in the midst of the late declining phase of Solar Cycle 24. In particular, we focus on two successive coronal mass ejections (CMEs) and a following high-speed stream (HSS) on their way towards Earth and Mars. We find that the first CME impacted both planets, whilst the second caused a strong magnetic storm at Earth and went on to miss Mars, which nevertheless experienced space weather effects from the stream interacting region (SIR) preceding the HSS. Analysis of remote-sensing and in-situ data supported by heliospheric modelling suggests that CME--HSS interaction resulted in the second CME rotating and deflecting in interplanetary space, highlighting that accurately reproducing the ambient solar wind is crucial even during "simpler" solar minimum periods. Lastly, we discuss the upstream solar wind conditions and transient structures responsible for driving space weather effects at Earth and Mars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.05760v1-abstract-full').style.display = 'none'; document.getElementById('2209.05760v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">27 pages, 7 figures, 1 table, accepted for publication in Space Weather</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.03635">arXiv:2209.03635</a> <span> [<a href="https://arxiv.org/pdf/2209.03635">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/25c2cfeb.2b22d58b">10.3847/25c2cfeb.2b22d58b <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space: Need for contextual energetic particle measurements at Earth and supporting distributed observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Corti%2C+C">Claudio Corti</a>, <a href="/search/astro-ph?searchtype=author&query=Whitman%2C+K">Kathryn Whitman</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+R">Ravindra Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Rankin%2C+J">Jamie Rankin</a>, <a href="/search/astro-ph?searchtype=author&query=Strauss%2C+D+T">Du Toit Strauss</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Turner%2C+D">Drew Turner</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+T+Y">Thomas Y Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2209.03635v1-abstract-short" style="display: inline;"> The particle and radiation environment in cis-lunar space is becoming increasingly important as more hardware and human assets occupy various orbits around the Earth and space exploration efforts turn to the Moon and beyond. Since 2020, the total number of satellites in orbit has approximately doubled, highlighting the growing dependence on space-based resources. Through NASA's upcoming Artemis mi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.03635v1-abstract-full').style.display = 'inline'; document.getElementById('2209.03635v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.03635v1-abstract-full" style="display: none;"> The particle and radiation environment in cis-lunar space is becoming increasingly important as more hardware and human assets occupy various orbits around the Earth and space exploration efforts turn to the Moon and beyond. Since 2020, the total number of satellites in orbit has approximately doubled, highlighting the growing dependence on space-based resources. Through NASA's upcoming Artemis missions, humans will spend more time in cis-lunar space than ever before supported by the expansive infrastructure required for extended missions to the Moon, including a surface habitat, a communications network, and the Lunar Gateway. This paper focuses on galactic cosmic rays (GCRs) and solar energetic particles (SEPs) that create a dynamic and varying radiation environment within these regions. GCRs are particles of hundreds of MeV/nucleon (MeV/n) and above generated in highly energetic astrophysical environments in the Milky Way Galaxy, such as supernovae and pulsars, and beyond. These particles impinge isotropically on the heliosphere and are filtered down to 1 AU, experiencing modulation in energy and intensity on multiple timescales, from hours to decades, due to the solar magnetic cycle and other transient phenomena. SEPs are particles with energies up to thousands of MeV/n that are accelerated in eruptive events on the Sun and flood the inner heliosphere causing sudden and drastic increases in the particle environment on timescales of minutes to days. This paper highlights a current and prospective future gap in energetic particle measurements in the hundreds of MeV/n. We recommend key observations near Earth to act as a baseline as well as distributed measurements in the heliosphere, magnetosphere, and lunar surface to improve the scientific understanding of these particle populations and sources. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.03635v1-abstract-full').style.display = 'none'; document.getElementById('2209.03635v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 1 figure. White Paper submitted to Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.13034">arXiv:2202.13034</a> <span> [<a href="https://arxiv.org/pdf/2202.13034">pdf</a>, <a href="https://arxiv.org/format/2202.13034">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ac589b">10.3847/1538-4357/ac589b <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Coronal Mass Ejections and Dimmings: A Comparative Study using MHD Simulations and SDO Observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Jin%2C+M">Meng Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Cheung%2C+M+C+M">Mark C. M. Cheung</a>, <a href="/search/astro-ph?searchtype=author&query=DeRosa%2C+M+L">Marc L. DeRosa</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Schrijver%2C+C+J">Carolus J. Schrijver</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2202.13034v1-abstract-short" style="display: inline;"> Solar coronal dimmings have been observed extensively in the past two decades. Due to their close association with coronal mass ejections (CMEs), there is a critical need to improve our understanding of the physical processes that cause dimmings as well as their relationship with CMEs. In this study, we investigate coronal dimmings by combining simulation and observational efforts. By utilizing a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.13034v1-abstract-full').style.display = 'inline'; document.getElementById('2202.13034v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.13034v1-abstract-full" style="display: none;"> Solar coronal dimmings have been observed extensively in the past two decades. Due to their close association with coronal mass ejections (CMEs), there is a critical need to improve our understanding of the physical processes that cause dimmings as well as their relationship with CMEs. In this study, we investigate coronal dimmings by combining simulation and observational efforts. By utilizing a data-constrained global magnetohydrodynamics model (AWSoM: Alfven-wave Solar Model), we simulate coronal dimmings resulting from different CME energetics and flux rope configurations. We synthesize the emissions of different EUV spectral bands/lines and compare with SDO/AIA and EVE observations. A detailed analysis of the simulation and observation data suggests that the transient dimming / brightening are related to plasma heating processes, while the long-lasting core and remote dimmings are caused by mass loss process induced by the CME. Moreover, the interaction between the erupting flux rope with different orientations and the global solar corona could significantly influence the coronal dimming patterns. Using metrics such as dimming depth and dimming slope, we investigate the relationship between dimmings and CME properties (e.g., CME mass, CME speed) in the simulation. Our result suggests that coronal dimmings encode important information about the associated CMEs, which provides a physical basis for detecting stellar CMEs from distant solar-like stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.13034v1-abstract-full').style.display = 'none'; document.getElementById('2202.13034v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages, 9 figures, accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.07214">arXiv:2202.07214</a> <span> [<a href="https://arxiv.org/pdf/2202.07214">pdf</a>, <a href="https://arxiv.org/format/2202.07214">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1029/2021SW002894">10.1029/2021SW002894 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Assessing the Influence of Input Magnetic Maps on Global Modeling of the Solar Wind and CME-driven Shock in the 2013 April 11 Event </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Jin%2C+M">Meng Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+C+M+S">Christina M. S. Cohen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2202.07214v1-abstract-short" style="display: inline;"> In the past decade, significant efforts have been made in developing physics-based solar wind and coronal mass ejection (CME) models, which have been or are being transferred to national centers (e.g., SWPC, CCMC) to enable space weather predictive capability. However, the input data coverage for space weather forecasting is extremely limited. One major limitation is the solar magnetic field measu… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.07214v1-abstract-full').style.display = 'inline'; document.getElementById('2202.07214v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.07214v1-abstract-full" style="display: none;"> In the past decade, significant efforts have been made in developing physics-based solar wind and coronal mass ejection (CME) models, which have been or are being transferred to national centers (e.g., SWPC, CCMC) to enable space weather predictive capability. However, the input data coverage for space weather forecasting is extremely limited. One major limitation is the solar magnetic field measurements, which are used to specify the inner boundary conditions of the global magnetohydrodynamic (MHD) models. In this study, using the Alfven wave solar model (AWSoM), we quantitatively assess the influence of the magnetic field map input (synoptic/diachronic vs. synchronic magnetic maps) on the global modeling of the solar wind and the CME-driven shock in the 2013 April 11 solar energetic particle (SEP) event. Our study shows that due to the inhomogeneous background solar wind and dynamical evolution of the CME, the CME-driven shock parameters change significantly both spatially and temporally as the CME propagates through the heliosphere. The input magnetic map has a great impact on the shock connectivity and shock properties in the global MHD simulation. Therefore this study illustrates the importance of taking into account the model uncertainty due to the imperfect magnetic field measurements when using the model to provide space weather predictions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.07214v1-abstract-full').style.display = 'none'; document.getElementById('2202.07214v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">24 pages, 8 figures, accepted for publication in Space Weather</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.08408">arXiv:2110.08408</a> <span> [<a href="https://arxiv.org/pdf/2110.08408">pdf</a>, <a href="https://arxiv.org/format/2110.08408">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s11214-021-00857-0">10.1007/s11214-021-00857-0 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Understanding the Origins of Problem Geomagnetic Storms Associated With "Stealth" Coronal Mass Ejections </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Mulligan%2C+T">Tamitha Mulligan</a>, <a href="/search/astro-ph?searchtype=author&query=Kilpua%2C+E+K+J">Emilia K. J. Kilpua</a>, <a href="/search/astro-ph?searchtype=author&query=Lynch%2C+B+J">Benjamin J. Lynch</a>, <a href="/search/astro-ph?searchtype=author&query=Mierla%2C+M">Marilena Mierla</a>, <a href="/search/astro-ph?searchtype=author&query=O%27Kane%2C+J">Jennifer O'Kane</a>, <a href="/search/astro-ph?searchtype=author&query=Pagano%2C+P">Paolo Pagano</a>, <a href="/search/astro-ph?searchtype=author&query=Palmerio%2C+E">Erika Palmerio</a>, <a href="/search/astro-ph?searchtype=author&query=Pomoell%2C+J">Jens Pomoell</a>, <a href="/search/astro-ph?searchtype=author&query=Richardson%2C+I+G">Ian G. Richardson</a>, <a href="/search/astro-ph?searchtype=author&query=Rodriguez%2C+L">Luciano Rodriguez</a>, <a href="/search/astro-ph?searchtype=author&query=Rouillard%2C+A+P">Alexis P. Rouillard</a>, <a href="/search/astro-ph?searchtype=author&query=Sinha%2C+S">Suvadip Sinha</a>, <a href="/search/astro-ph?searchtype=author&query=Srivastava%2C+N">Nandita Srivastava</a>, <a href="/search/astro-ph?searchtype=author&query=Talpeanu%2C+D">Dana-Camelia Talpeanu</a>, <a href="/search/astro-ph?searchtype=author&query=Yardley%2C+S+L">Stephanie L. Yardley</a>, <a href="/search/astro-ph?searchtype=author&query=Zhukov%2C+A+N">Andrei N. Zhukov</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2110.08408v1-abstract-short" style="display: inline;"> Geomagnetic storms are an important aspect of space weather and can result in significant impacts on space- and ground-based assets. The majority of strong storms are associated with the passage of interplanetary coronal mass ejections (ICMEs) in the near-Earth environment. In many cases, these ICMEs can be traced back unambiguously to a specific coronal mass ejection (CME) and solar activity on t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.08408v1-abstract-full').style.display = 'inline'; document.getElementById('2110.08408v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.08408v1-abstract-full" style="display: none;"> Geomagnetic storms are an important aspect of space weather and can result in significant impacts on space- and ground-based assets. The majority of strong storms are associated with the passage of interplanetary coronal mass ejections (ICMEs) in the near-Earth environment. In many cases, these ICMEs can be traced back unambiguously to a specific coronal mass ejection (CME) and solar activity on the frontside of the Sun. Hence, predicting the arrival of ICMEs at Earth from routine observations of CMEs and solar activity currently makes a major contribution to the forecasting of geomagnetic storms. However, it is clear that some ICMEs, which may also cause enhanced geomagnetic activity, cannot be traced back to an observed CME, or, if the CME is identified, its origin may be elusive or ambiguous in coronal images. Such CMEs have been termed "stealth CMEs." In this review, we focus on these "problem" geomagnetic storms in the sense that the solar/CME precursors are enigmatic and stealthy. We start by reviewing evidence for stealth CMEs discussed in past studies. We then identify several moderate to strong geomagnetic storms (minimum Dst < -50 nT) in solar cycle 24 for which the related solar sources and/or CMEs are unclear and apparently stealthy. We discuss the solar and in situ circumstances of these events and identify several scenarios that may account for their elusive solar signatures. These range from observational limitations (e.g., a coronagraph near Earth may not detect an incoming CME if it is diffuse and not wide enough) to the possibility that there is a class of mass ejections from the Sun that have only weak or hard-to-observe coronal signatures. In particular, some of these sources are only clearly revealed by considering the evolution of coronal structures over longer time intervals than is usually considered. We also review a variety of numerical modelling approaches... <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.08408v1-abstract-full').style.display = 'none'; document.getElementById('2110.08408v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">60 pages, 25 figures, 5 tables. Accepted for publication in Space Science Reviews</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Space Sci Rev 217, 82 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2109.05570">arXiv:2109.05570</a> <span> [<a href="https://arxiv.org/pdf/2109.05570">pdf</a>, <a href="https://arxiv.org/format/2109.05570">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202141009">10.1051/0004-6361/202141009 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Long Period of 3He-rich Solar Energetic Particles Measured by Solar Orbiter on 2020 November 17-23 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bucik%2C+R">R. Bucik</a>, <a href="/search/astro-ph?searchtype=author&query=Mason%2C+G+M">G. M. Mason</a>, <a href="/search/astro-ph?searchtype=author&query=Gomez-Herrero%2C+R">R. Gomez-Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Lario%2C+D">D. Lario</a>, <a href="/search/astro-ph?searchtype=author&query=Balmaceda%2C+L">L. Balmaceda</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Krupar%2C+V">V. Krupar</a>, <a href="/search/astro-ph?searchtype=author&query=Dresing%2C+N">N. Dresing</a>, <a href="/search/astro-ph?searchtype=author&query=Ho%2C+G+C">G. C. Ho</a>, <a href="/search/astro-ph?searchtype=author&query=Allen%2C+R+C">R. C. Allen</a>, <a href="/search/astro-ph?searchtype=author&query=Carcaboso%2C+F">F. Carcaboso</a>, <a href="/search/astro-ph?searchtype=author&query=Rodriguez-Pacheco%2C+J">J. Rodriguez-Pacheco</a>, <a href="/search/astro-ph?searchtype=author&query=Schuller%2C+F">F. Schuller</a>, <a href="/search/astro-ph?searchtype=author&query=Warmuth%2C+A">A. Warmuth</a>, <a href="/search/astro-ph?searchtype=author&query=Wimmer-Schweingruber%2C+R+F">R. F. Wimmer-Schweingruber</a>, <a href="/search/astro-ph?searchtype=author&query=von+Forstner%2C+J+L+F">J. L. Freiherr von Forstner</a>, <a href="/search/astro-ph?searchtype=author&query=Andrews%2C+G+B">G. B. Andrews</a>, <a href="/search/astro-ph?searchtype=author&query=Berger%2C+L">L. Berger</a>, <a href="/search/astro-ph?searchtype=author&query=Cernuda%2C+I">I. Cernuda</a>, <a href="/search/astro-ph?searchtype=author&query=Lara%2C+F+E">F. Espinosa Lara</a>, <a href="/search/astro-ph?searchtype=author&query=Lees%2C+W+J">W. J. Lees</a>, <a href="/search/astro-ph?searchtype=author&query=Martin%2C+C">C. Martin</a>, <a href="/search/astro-ph?searchtype=author&query=Pacheco%2C+D">D. Pacheco</a>, <a href="/search/astro-ph?searchtype=author&query=Prieto%2C+M">M. Prieto</a>, <a href="/search/astro-ph?searchtype=author&query=Sanchez-Prieto%2C+S">S. Sanchez-Prieto</a> , et al. (9 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2109.05570v1-abstract-short" style="display: inline;"> We report observations of a relatively long period of 3He-rich solar energetic particles (SEPs) measured by Solar Orbiter. The period consists of several well-resolved ion injections. The high-resolution STEREO-A imaging observations reveal that the injections coincide with EUV jets/brightenings near the east limb, not far from the nominal magnetic connection of Solar Orbiter. The jets originated… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.05570v1-abstract-full').style.display = 'inline'; document.getElementById('2109.05570v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.05570v1-abstract-full" style="display: none;"> We report observations of a relatively long period of 3He-rich solar energetic particles (SEPs) measured by Solar Orbiter. The period consists of several well-resolved ion injections. The high-resolution STEREO-A imaging observations reveal that the injections coincide with EUV jets/brightenings near the east limb, not far from the nominal magnetic connection of Solar Orbiter. The jets originated in two adjacent, large, and complex active regions as observed by the Solar Dynamics Observatory when the regions rotated to the Earth's view. It appears that the sustained ion injections were related to the complex configuration of the sunspot group and the long period of 3He-rich SEPs to the longitudinal extent covered by the group during the analyzed time period. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.05570v1-abstract-full').style.display = 'none'; document.getElementById('2109.05570v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">accepted for publication in A&A, Letters to the Editor</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 656, L11 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2107.10257">arXiv:2107.10257</a> <span> [<a href="https://arxiv.org/pdf/2107.10257">pdf</a>, <a href="https://arxiv.org/format/2107.10257">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202039960">10.1051/0004-6361/202039960 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The unusual widespread solar energetic particle event on 2013 August 19. Solar origin and particle longitudinal distribution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Rodr%C3%ADguez-Garc%C3%ADa%2C+L">L. Rodr铆guez-Garc铆a</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez-Herrero%2C+R">R. G贸mez-Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Zouganelis%2C+I">I. Zouganelis</a>, <a href="/search/astro-ph?searchtype=author&query=Balmaceda%2C+L">L. Balmaceda</a>, <a href="/search/astro-ph?searchtype=author&query=Nieves-Chinchilla%2C+T">T. Nieves-Chinchilla</a>, <a href="/search/astro-ph?searchtype=author&query=Dresing%2C+N">N. Dresing</a>, <a href="/search/astro-ph?searchtype=author&query=Dumbovic%2C+M">M. Dumbovic</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Carcaboso%2C+F">F. Carcaboso</a>, <a href="/search/astro-ph?searchtype=author&query=Santos%2C+L+F+G+d">L. F. G. dos Santos</a>, <a href="/search/astro-ph?searchtype=author&query=Jian%2C+L+K">L. K. Jian</a>, <a href="/search/astro-ph?searchtype=author&query=Mays%2C+L">L. Mays</a>, <a href="/search/astro-ph?searchtype=author&query=Williams%2C+D">D. Williams</a>, <a href="/search/astro-ph?searchtype=author&query=Rodr%C3%ADguez-Pacheco%2C+J">J. Rodr铆guez-Pacheco</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2107.10257v1-abstract-short" style="display: inline;"> Context: Late on 2013 August 19, STEREO-A, STEREO-B, MESSENGER, Mars Odyssey, and the L1 spacecraft, spanning a longitudinal range of 222掳 in the ecliptic plane, observed an energetic particle flux increase. The widespread solar energetic particle (SEP) event was associated with a coronal mass ejection (CME) that came from a region located near the far-side central meridian from Earth's perspectiv… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.10257v1-abstract-full').style.display = 'inline'; document.getElementById('2107.10257v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.10257v1-abstract-full" style="display: none;"> Context: Late on 2013 August 19, STEREO-A, STEREO-B, MESSENGER, Mars Odyssey, and the L1 spacecraft, spanning a longitudinal range of 222掳 in the ecliptic plane, observed an energetic particle flux increase. The widespread solar energetic particle (SEP) event was associated with a coronal mass ejection (CME) that came from a region located near the far-side central meridian from Earth's perspective. The CME erupted in two stages, and was accompanied by a late M-class flare observed as a post-eruptive arcade, persisting low-frequency (interplanetary) type II and groups of shock-accelerated type III radio bursts, all of them making this SEP event unusual. Aims: There are two main objectives of this study, disentangling the reasons for the different intensity-time profiles observed by the spacecraft, especially at MESSENGER and STEREO-A locations, longitudinally separated by only 15掳, and unravelling the single solar source related with the widespread SEP event. Results: The solar source associated with the widespread SEP event is the shock driven by the CME, as the flare observed as a post-eruptive arcade is too late to explain the estimated particle onset. The different intensity-time profiles observed by STEREO-A, located at 0.97 au, and MESSENGER, at 0.33 au, can be interpreted as enhanced particle scattering beyond Mercury's orbit. The longitudinal extent of the shock does not explain by itself the wide spread of particles in the heliosphere. The particle increase observed at L1 may be attributed to cross-field diffusion transport, and this is also the case for STEREO-B, at least until the spacecraft is eventually magnetically connected to the shock when it reaches ~0.6 au. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.10257v1-abstract-full').style.display = 'none'; document.getElementById('2107.10257v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">23 pages, 13 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 653, A137 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.15591">arXiv:2106.15591</a> <span> [<a href="https://arxiv.org/pdf/2106.15591">pdf</a>, <a href="https://arxiv.org/format/2106.15591">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ac4223">10.3847/1538-4357/ac4223 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the Physics of the Solar Atmosphere with the Multi-slit Solar Explorer (MUSE): II. Flares and Eruptions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cheung%2C+M+C+M">Mark C. M. Cheung</a>, <a href="/search/astro-ph?searchtype=author&query=Mart%C3%ADnez-Sykora%2C+J">Juan Mart铆nez-Sykora</a>, <a href="/search/astro-ph?searchtype=author&query=Testa%2C+P">Paola Testa</a>, <a href="/search/astro-ph?searchtype=author&query=De+Pontieu%2C+B">Bart De Pontieu</a>, <a href="/search/astro-ph?searchtype=author&query=Chintzoglou%2C+G">Georgios Chintzoglou</a>, <a href="/search/astro-ph?searchtype=author&query=Rempel%2C+M">Matthias Rempel</a>, <a href="/search/astro-ph?searchtype=author&query=Polito%2C+V">Vanessa Polito</a>, <a href="/search/astro-ph?searchtype=author&query=Kerr%2C+G+S">Graham S. Kerr</a>, <a href="/search/astro-ph?searchtype=author&query=Reeves%2C+K+K">Katharine K. Reeves</a>, <a href="/search/astro-ph?searchtype=author&query=Fletcher%2C+L">Lyndsay Fletcher</a>, <a href="/search/astro-ph?searchtype=author&query=Jin%2C+M">Meng Jin</a>, <a href="/search/astro-ph?searchtype=author&query=N%C3%B3brega-Siverio%2C+D">Daniel N贸brega-Siverio</a>, <a href="/search/astro-ph?searchtype=author&query=Danilovic%2C+S">Sanja Danilovic</a>, <a href="/search/astro-ph?searchtype=author&query=Antolin%2C+P">Patrick Antolin</a>, <a href="/search/astro-ph?searchtype=author&query=Allred%2C+J">Joel Allred</a>, <a href="/search/astro-ph?searchtype=author&query=Hansteen%2C+V">Viggo Hansteen</a>, <a href="/search/astro-ph?searchtype=author&query=Ugarte-Urra%2C+I">Ignacio Ugarte-Urra</a>, <a href="/search/astro-ph?searchtype=author&query=DeLuca%2C+E">Edward DeLuca</a>, <a href="/search/astro-ph?searchtype=author&query=Longcope%2C+D">Dana Longcope</a>, <a href="/search/astro-ph?searchtype=author&query=Takasao%2C+S">Shinsuke Takasao</a>, <a href="/search/astro-ph?searchtype=author&query=DeRosa%2C+M">Marc DeRosa</a>, <a href="/search/astro-ph?searchtype=author&query=Boerner%2C+P">Paul Boerner</a>, <a href="/search/astro-ph?searchtype=author&query=Jaeggli%2C+S">Sarah Jaeggli</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Daw%2C+A">Adrian Daw</a> , et al. (3 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2106.15591v3-abstract-short" style="display: inline;"> Current state-of-the-art spectrographs cannot resolve the fundamental spatial (sub-arcseconds) and temporal scales (less than a few tens of seconds) of the coronal dynamics of solar flares and eruptive phenomena. The highest resolution coronal data to date are based on imaging, which is blind to many of the processes that drive coronal energetics and dynamics. As shown by IRIS for the low solar at… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.15591v3-abstract-full').style.display = 'inline'; document.getElementById('2106.15591v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.15591v3-abstract-full" style="display: none;"> Current state-of-the-art spectrographs cannot resolve the fundamental spatial (sub-arcseconds) and temporal scales (less than a few tens of seconds) of the coronal dynamics of solar flares and eruptive phenomena. The highest resolution coronal data to date are based on imaging, which is blind to many of the processes that drive coronal energetics and dynamics. As shown by IRIS for the low solar atmosphere, we need high-resolution spectroscopic measurements with simultaneous imaging to understand the dominant processes. In this paper: (1) we introduce the Multi-slit Solar Explorer (MUSE), a spaceborne observatory to fill this observational gap by providing high-cadence (<20 s), sub-arcsecond resolution spectroscopic rasters over an active region size of the solar transition region and corona; (2) using advanced numerical models, we demonstrate the unique diagnostic capabilities of MUSE for exploring solar coronal dynamics, and for constraining and discriminating models of solar flares and eruptions; (3) we discuss the key contributions MUSE would make in addressing the science objectives of the Next Generation Solar Physics Mission (NGSPM), and how MUSE, the high-throughput EUV Solar Telescope (EUVST) and the Daniel K Inouye Solar Telescope (and other ground-based observatories) can operate as a distributed implementation of the NGSPM. This is a companion paper to De Pontieu et al. (2021; arXiv:2106.15584), which focuses on investigating coronal heating with MUSE. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.15591v3-abstract-full').style.display = 'none'; document.getElementById('2106.15591v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">42 pages, 22 figures, submitted to ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.07571">arXiv:2106.07571</a> <span> [<a href="https://arxiv.org/pdf/2106.07571">pdf</a>, <a href="https://arxiv.org/format/2106.07571">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3389/fspas.2021.695966">10.3389/fspas.2021.695966 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Investigating Remote-sensing Techniques to Reveal Stealth Coronal Mass Ejections </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Palmerio%2C+E">Erika Palmerio</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Mulligan%2C+T">Tamitha Mulligan</a>, <a href="/search/astro-ph?searchtype=author&query=Mierla%2C+M">Marilena Mierla</a>, <a href="/search/astro-ph?searchtype=author&query=O%27Kane%2C+J">Jennifer O'Kane</a>, <a href="/search/astro-ph?searchtype=author&query=Richardson%2C+I+G">Ian G. Richardson</a>, <a href="/search/astro-ph?searchtype=author&query=Sinha%2C+S">Suvadip Sinha</a>, <a href="/search/astro-ph?searchtype=author&query=Srivastava%2C+N">Nandita Srivastava</a>, <a href="/search/astro-ph?searchtype=author&query=Yardley%2C+S+L">Stephanie L. Yardley</a>, <a href="/search/astro-ph?searchtype=author&query=Zhukov%2C+A+N">Andrei N. Zhukov</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2106.07571v1-abstract-short" style="display: inline;"> Eruptions of coronal mass ejections (CMEs) from the Sun are usually associated with a number of signatures that can be identified in solar disc imagery. However, there are cases in which a CME that is well observed in coronagraph data is missing a clear low-coronal counterpart. These events have received attention during recent years, mainly as a result of the increased availability of multi-point… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.07571v1-abstract-full').style.display = 'inline'; document.getElementById('2106.07571v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.07571v1-abstract-full" style="display: none;"> Eruptions of coronal mass ejections (CMEs) from the Sun are usually associated with a number of signatures that can be identified in solar disc imagery. However, there are cases in which a CME that is well observed in coronagraph data is missing a clear low-coronal counterpart. These events have received attention during recent years, mainly as a result of the increased availability of multi-point observations, and are now known as 'stealth CMEs'. In this work, we analyse examples of stealth CMEs featuring various levels of ambiguity. All the selected case studies produced a large-scale CME detected by coronagraphs and were observed from at least one secondary viewpoint, enabling a priori knowledge of their approximate source region. To each event, we apply several image processing and geometric techniques with the aim to evaluate whether such methods can provide additional information compared to the study of "normal" intensity images. We are able to identify at least weak eruptive signatures for all events upon careful investigation of remote-sensing data, noting that differently processed images may be needed to properly interpret and analyse elusive observations. We also find that the effectiveness of geometric techniques strongly depends on the CME propagation direction with respect to the observers and the relative spacecraft separation. Being able to observe and therefore forecast stealth CMEs is of great importance in the context of space weather, since such events are occasionally the solar counterparts of so-called 'problem geomagnetic storms'. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.07571v1-abstract-full').style.display = 'none'; document.getElementById('2106.07571v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">26 pages, 8 figures, 1 table, accepted for publication in Frontiers in Astronomy and Space Sciences</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2012.15390">arXiv:2012.15390</a> <span> [<a href="https://arxiv.org/pdf/2012.15390">pdf</a>, <a href="https://arxiv.org/ps/2012.15390">ps</a>, <a href="https://arxiv.org/format/2012.15390">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/abd62d">10.3847/1538-4357/abd62d <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Temperature in Solar Sources of 3He-rich Solar Energetic Particles and Relation to Ion Abundances </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bucik%2C+R">R. Bucik</a>, <a href="/search/astro-ph?searchtype=author&query=Mulay%2C+S+M">S. M. Mulay</a>, <a href="/search/astro-ph?searchtype=author&query=Mason%2C+G+M">G. M. Mason</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+M+I">M. I. Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Dayeh%2C+M+A">M. A. Dayeh</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2012.15390v1-abstract-short" style="display: inline;"> 3He-rich solar energetic particles (SEPs) are believed to be accelerated in solar flares or jets by a mechanism that depends on the ion charge-to-mass (Q/M) ratio. It implies that the flare plasma characteristics (e.g., temperature) may be effective in determining the elemental abundances of 3He-rich SEPs. This study examines the relation between the suprathermal (<0.2 MeV/nuc) abundances of the H… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.15390v1-abstract-full').style.display = 'inline'; document.getElementById('2012.15390v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2012.15390v1-abstract-full" style="display: none;"> 3He-rich solar energetic particles (SEPs) are believed to be accelerated in solar flares or jets by a mechanism that depends on the ion charge-to-mass (Q/M) ratio. It implies that the flare plasma characteristics (e.g., temperature) may be effective in determining the elemental abundances of 3He-rich SEPs. This study examines the relation between the suprathermal (<0.2 MeV/nuc) abundances of the He-Fe ions measured on the Advanced Composition Explorer and temperature in the solar sources for 24 3He-rich SEP events in the period 2010-2015. The differential emission measure technique is applied to derive the temperature of the source regions from the extreme ultraviolet imaging observations on the Solar Dynamics Observatory. The obtained temperature distribution peaks at 2.0-2.5 MK that is surprisingly consistent with earlier findings based on in-situ elemental abundance or charge state measurements. We have found a significant anti-correlation between 3He/4He ratio and solar source temperature with a coefficient -0.6. It is most likely caused by non-charge-stripping processes, as both isotopes would be fully ionized in the inferred temperature range. This study shows that the elemental ratios 4He/O, N/O, Ne/O, Si/O, S/O, Ca/O, Fe/O generally behave with temperature as expected from abundance enhancement calculations at ionization equilibrium. The C and Mg, the two species with small changes in the Q/M ratio in the obtained temperature range, show no such behavior with temperature and could be influenced by similar processes as for the 3He/4He ratio. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.15390v1-abstract-full').style.display = 'none'; document.getElementById('2012.15390v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 December, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2012.06116">arXiv:2012.06116</a> <span> [<a href="https://arxiv.org/pdf/2012.06116">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> </div> <p class="title is-5 mathjax"> Earth-affecting Solar Transients: A Review of Progresses in Solar Cycle 24 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+J">Jie Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Temmer%2C+M">Manuela Temmer</a>, <a href="/search/astro-ph?searchtype=author&query=Gopalswamy%2C+N">Nat Gopalswamy</a>, <a href="/search/astro-ph?searchtype=author&query=Malandraki%2C+O">Olga Malandraki</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Patsourakos%2C+S">Spiros Patsourakos</a>, <a href="/search/astro-ph?searchtype=author&query=Shen%2C+F">Fang Shen</a>, <a href="/search/astro-ph?searchtype=author&query=Vr%C5%A1nak%2C+B">Bojan Vr拧nak</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+Y">Yuming Wang</a>, <a href="/search/astro-ph?searchtype=author&query=Webb%2C+D">David Webb</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+M+I">Mihir I. Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Dissauer%2C+K">Karin Dissauer</a>, <a href="/search/astro-ph?searchtype=author&query=Dresing%2C+N">Nina Dresing</a>, <a href="/search/astro-ph?searchtype=author&query=Dumbovi%C4%87%2C+M">Mateja Dumbovi膰</a>, <a href="/search/astro-ph?searchtype=author&query=Feng%2C+X">Xueshang Feng</a>, <a href="/search/astro-ph?searchtype=author&query=Heinemann%2C+S+G">Stephan G. Heinemann</a>, <a href="/search/astro-ph?searchtype=author&query=Laurenza%2C+M">Monica Laurenza</a>, <a href="/search/astro-ph?searchtype=author&query=Lugaz%2C+N">No茅 Lugaz</a>, <a href="/search/astro-ph?searchtype=author&query=Zhuang%2C+B">Bin Zhuang</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2012.06116v1-abstract-short" style="display: inline;"> This review article summarizes the advancement in the studies of Earth-affecting solar transients in the last decade that encompasses most of solar cycle 24. The Sun Earth is an integrated physical system in which the space environment of the Earth sustains continuous influence from mass, magnetic field and radiation energy output of the Sun in varying time scales from minutes to millennium. This… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.06116v1-abstract-full').style.display = 'inline'; document.getElementById('2012.06116v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2012.06116v1-abstract-full" style="display: none;"> This review article summarizes the advancement in the studies of Earth-affecting solar transients in the last decade that encompasses most of solar cycle 24. The Sun Earth is an integrated physical system in which the space environment of the Earth sustains continuous influence from mass, magnetic field and radiation energy output of the Sun in varying time scales from minutes to millennium. This article addresses short time scale events, from minutes to days that directly cause transient disturbances in the Earth space environment and generate intense adverse effects on advanced technological systems of human society. Such transient events largely fall into the following four types: (1) solar flares, (2) coronal mass ejections (CMEs) including their interplanetary counterparts ICMEs, (3) solar energetic particle (SEP) events, and (4) stream interaction regions (SIRs) including corotating interaction regions (CIRs). In the last decade, the unprecedented multi viewpoint observations of the Sun from space, enabled by STEREO Ahead/Behind spacecraft in combination with a suite of observatories along the Sun-Earth lines, have provided much more accurate and global measurements of the size, speed, propagation direction and morphology of CMEs in both 3-D and over a large volume in the heliosphere. Several advanced MHD models have been developed to simulate realistic CME events from the initiation on the Sun until their arrival at 1 AU. Much progress has been made on detailed kinematic and dynamic behaviors of CMEs, including non-radial motion, rotation and deformation of CMEs, CME-CME interaction, and stealth CMEs and problematic ICMEs. The knowledge about SEPs has also been significantly improved. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.06116v1-abstract-full').style.display = 'none'; document.getElementById('2012.06116v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 December, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Review article, 184 pages</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.08062">arXiv:2007.08062</a> <span> [<a href="https://arxiv.org/pdf/2007.08062">pdf</a>, <a href="https://arxiv.org/format/2007.08062">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/aba621">10.3847/1538-4357/aba621 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Statistical Analysis of the Relation between Coronal Mass Ejections and Solar Energetic Particles </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kihara%2C+K">Kosuke Kihara</a>, <a href="/search/astro-ph?searchtype=author&query=Huang%2C+Y">Yuwei Huang</a>, <a href="/search/astro-ph?searchtype=author&query=Nishimura%2C+N">Nobuhiko Nishimura</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Yashiro%2C+S">Seiji Yashiro</a>, <a href="/search/astro-ph?searchtype=author&query=Ichimoto%2C+K">Kiyoshi Ichimoto</a>, <a href="/search/astro-ph?searchtype=author&query=Asai%2C+A">Ayumi Asai</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2007.08062v1-abstract-short" style="display: inline;"> To improve the forecasting capability of impactful solar energetic particle (SEP) events, the relation between coronal mass ejections (CMEs) and SEP events needs to be better understood. Here we present a statistical study of SEP occurrences and timescales with respect to the CME source locations and speeds, considering all 257 fast ($v_{CME}$ $\ge$ 900 km/s) and wide (angular width $\ge$ 60… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.08062v1-abstract-full').style.display = 'inline'; document.getElementById('2007.08062v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.08062v1-abstract-full" style="display: none;"> To improve the forecasting capability of impactful solar energetic particle (SEP) events, the relation between coronal mass ejections (CMEs) and SEP events needs to be better understood. Here we present a statistical study of SEP occurrences and timescales with respect to the CME source locations and speeds, considering all 257 fast ($v_{CME}$ $\ge$ 900 km/s) and wide (angular width $\ge$ 60$^{\circ}$) CMEs that occurred between December 2006 and October 2017. We associate them with SEP events at energies above 10 MeV. Examination of the source region of each CME reveals that CMEs more often accompany a SEP event if they originate from the longitude of E20-W100 relative to the observer. However, a SEP event could still be absent if the CME is $<$ 2000 km/s. For the associated CME-SEP pairs, we compute three timescales for each of the SEP events, following Kahler (2005, 2013); namely the timescale of the onset (TO), the rise time (TR), and the duration (TD). They are correlated with the longitude of the CME source region relative to the footpoint of the Parker spiral ($螖桅$) and $v_{CME}$. The TO tends to be short for $|螖桅|$ $<$ 60$^{\circ}$ . This trend is weaker for TR and TD. The SEP timescales are only weakly correlated with $v_{CME}$. Positive correlations of both TR and TD with $v_{CME}$ are seen in poorly connected (large $|螖桅|$) events. Additionally, TO appears to be negatively correlated with $v_{CME}$ for events with small $|螖桅|$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.08062v1-abstract-full').style.display = 'none'; document.getElementById('2007.08062v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">23 pages, 10 figures, accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2002.06249">arXiv:2002.06249</a> <span> [<a href="https://arxiv.org/pdf/2002.06249">pdf</a>, <a href="https://arxiv.org/format/2002.06249">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921320000575">10.1017/S1743921320000575 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Coronal Dimming as a Proxy for Stellar Coronal Mass Ejections </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Jin%2C+M">Meng Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Cheung%2C+M+C+M">Mark C. M. Cheung</a>, <a href="/search/astro-ph?searchtype=author&query=DeRosa%2C+M+L">Marc L. DeRosa</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Schrijver%2C+C+J">Carolus J. Schrijver</a>, <a href="/search/astro-ph?searchtype=author&query=France%2C+K">Kevin France</a>, <a href="/search/astro-ph?searchtype=author&query=Kowalski%2C+A">Adam Kowalski</a>, <a href="/search/astro-ph?searchtype=author&query=Mason%2C+J+P">James P. Mason</a>, <a href="/search/astro-ph?searchtype=author&query=Osten%2C+R">Rachel Osten</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2002.06249v1-abstract-short" style="display: inline;"> Solar coronal dimmings have been observed extensively in the past two decades and are believed to have close association with coronal mass ejections (CMEs). Recent study found that coronal dimming is the only signature that could differentiate powerful ares that have CMEs from those that do not. Therefore, dimming might be one of the best candidates to observe the stellar CMEs on distant Sun-like… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.06249v1-abstract-full').style.display = 'inline'; document.getElementById('2002.06249v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2002.06249v1-abstract-full" style="display: none;"> Solar coronal dimmings have been observed extensively in the past two decades and are believed to have close association with coronal mass ejections (CMEs). Recent study found that coronal dimming is the only signature that could differentiate powerful ares that have CMEs from those that do not. Therefore, dimming might be one of the best candidates to observe the stellar CMEs on distant Sun-like stars. In this study, we investigate the possibility of using coronal dimming as a proxy to diagnose stellar CMEs. By simulating a realistic solar CME event and corresponding coronal dimming using a global magnetohydrodynamics model (AWSoM: Alfven-wave Solar Model), we first demonstrate the capability of the model to reproduce solar observations. We then extend the model for simulating stellar CMEs by modifying the input magnetic flux density as well as the initial magnetic energy of the CME flux rope. Our result suggests that with improved instrument sensitivity, it is possible to detect the coronal dimming signals induced by the stellar CMEs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.06249v1-abstract-full').style.display = 'none'; document.getElementById('2002.06249v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, 4 figures, to appear in the Proceedings of IAU Symposium No. 354 - Solar and Stellar Magnetic Fields: Origins and Manifestations</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1911.05897">arXiv:1911.05897</a> <span> [<a href="https://arxiv.org/pdf/1911.05897">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ab57ff">10.3847/1538-4357/ab57ff <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Spectral Structures of Type II Solar Radio Bursts and Solar Energetic Particles </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Iwai%2C+K">Kazumasa Iwai</a>, <a href="/search/astro-ph?searchtype=author&query=Yashiro%2C+S">Seiji Yashiro</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Kubo%2C+Y">Yuki Kubo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1911.05897v1-abstract-short" style="display: inline;"> We investigated the relationship between the spectral structures of type II solar radio bursts in the hectometric and kilometric wavelength ranges and solar energetic particles (SEPs). To examine the statistical relationship between type II bursts and SEPs, we selected 26 coronal mass ejection (CME) events with similar characteristics (e.g., initial speed, angular width, and location) observed by… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1911.05897v1-abstract-full').style.display = 'inline'; document.getElementById('1911.05897v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1911.05897v1-abstract-full" style="display: none;"> We investigated the relationship between the spectral structures of type II solar radio bursts in the hectometric and kilometric wavelength ranges and solar energetic particles (SEPs). To examine the statistical relationship between type II bursts and SEPs, we selected 26 coronal mass ejection (CME) events with similar characteristics (e.g., initial speed, angular width, and location) observed by the Large Angle and Spectrometric Coronagraph (LASCO), regardless of the characteristics of the corresponding type II bursts and the SEP flux. Then, we compared associated type II bursts observed by the Radio and Plasma Wave Experiment (WAVES) onboard the Wind spacecraft and the SEP flux observed by the Geostationary Operational Environmental Satellite (GOES) orbiting around the Earth. We found that the bandwidth of the hectometric type II bursts and the peak flux of the SEPs has a positive correlation (with a correlation coefficient of 0.64). This result supports the idea that the nonthermal electrons of type II bursts and the nonthermal ions of SEPs are generated by the same shock and suggests that more SEPs may be generated for a wider or stronger CME shock with a longer duration. Our result also suggests that considering the spectral structures of type II bursts can improve the forecasting accuracy for the peak flux of gradual SEPs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1911.05897v1-abstract-full').style.display = 'none'; document.getElementById('1911.05897v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 November, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">24 pages, 6 figures, accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1910.03319">arXiv:1910.03319</a> <span> [<a href="https://arxiv.org/pdf/1910.03319">pdf</a>, <a href="https://arxiv.org/format/1910.03319">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s11207-020-1591-7">10.1007/s11207-020-1591-7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Comprehensive Characterization of Solar Eruptions With Remote and In-Situ Observations, and Modeling: The Major Solar Events on 4 November 2015 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cairns%2C+I+H">Iver H. Cairns</a>, <a href="/search/astro-ph?searchtype=author&query=Kozarev%2C+K+A">Kamen A. Kozarev</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Agueda%2C+N">Neus Agueda</a>, <a href="/search/astro-ph?searchtype=author&query=Battarbee%2C+M">Markus Battarbee</a>, <a href="/search/astro-ph?searchtype=author&query=Carley%2C+E+P">Eoin P. Carley</a>, <a href="/search/astro-ph?searchtype=author&query=Dresing%2C+N">Nina Dresing</a>, <a href="/search/astro-ph?searchtype=author&query=Gomez-Herrero%2C+R">Raul Gomez-Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Klein%2C+K">Karl-Ludwig Klein</a>, <a href="/search/astro-ph?searchtype=author&query=Lario%2C+D">David Lario</a>, <a href="/search/astro-ph?searchtype=author&query=Pomoell%2C+J">Jens Pomoell</a>, <a href="/search/astro-ph?searchtype=author&query=Salas-Matamoros%2C+C">Carolina Salas-Matamoros</a>, <a href="/search/astro-ph?searchtype=author&query=Veronig%2C+A+M">Astrid M. Veronig</a>, <a href="/search/astro-ph?searchtype=author&query=Li%2C+B">Bo Li</a>, <a href="/search/astro-ph?searchtype=author&query=McCauley%2C+P">Patrick McCauley</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1910.03319v1-abstract-short" style="display: inline;"> Solar energetic particles (SEPs) are an important product of solar activity. They are connected to solar active regions and flares, coronal mass ejections (CMEs), EUV waves, shocks, Type II and III radio emissions, and X-ray bursts. These phenomena are major probes of the partition of energy in solar eruptions, as well as for the organization, dynamics, and relaxation of coronal and interplanetary… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.03319v1-abstract-full').style.display = 'inline'; document.getElementById('1910.03319v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1910.03319v1-abstract-full" style="display: none;"> Solar energetic particles (SEPs) are an important product of solar activity. They are connected to solar active regions and flares, coronal mass ejections (CMEs), EUV waves, shocks, Type II and III radio emissions, and X-ray bursts. These phenomena are major probes of the partition of energy in solar eruptions, as well as for the organization, dynamics, and relaxation of coronal and interplanetary magnetic fields. Many of these phenomena cause terrestrial space weather, posing multiple hazards for humans and their technology from space to the ground. Since particular flares, shocks, CMEs, and EUV waves produce SEP events but others do not, since propagation effects from the low corona to 1 AU appear important for some events but not others, and since Type II and III radio emissions and X-ray bursts are sometimes produced by energetic particles leaving these acceleration sites, it is necessary to study the whole system with a multi-frequency and multi-instrument perspective that combines both in-situ and remote observations with detailed modelling of phenomena. This article demonstrates this comprehensive approach, and shows its necessity, by analysing a trio of unusual and striking solar eruptions, radio and X-ray bursts, and SEP events that occurred on 4 November 2015. These events show both strong similarities and differences from standard events and each other, despite having very similar interplanetary conditions and only two are sites and CME genesis regions. They are therefore major targets for further in-depth observational studies, and for testing both existing and new theories and models. Based on the very limited modelling available we identify the aspects that are and are not understood, and we discuss ideas that may lead to improved understanding of the SEP, radio, and space-weather events. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.03319v1-abstract-full').style.display = 'none'; document.getElementById('1910.03319v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 October, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">56 pages, 25 figures; Accepted for publication in Solar Physics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1812.07735">arXiv:1812.07735</a> <span> [<a href="https://arxiv.org/pdf/1812.07735">pdf</a>, <a href="https://arxiv.org/ps/1812.07735">ps</a>, <a href="https://arxiv.org/format/1812.07735">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/aaf37f">10.3847/2041-8213/aaf37f <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> 3He-Rich Solar Energetic Particles from Sunspot Jets </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bucik%2C+R">R. Bucik</a>, <a href="/search/astro-ph?searchtype=author&query=Wiedenbeck%2C+M+E">M. E. Wiedenbeck</a>, <a href="/search/astro-ph?searchtype=author&query=Mason%2C+G+M">G. M. Mason</a>, <a href="/search/astro-ph?searchtype=author&query=Gomez-Herrero%2C+R">R. Gomez-Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">N. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+L">L. Wang</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1812.07735v1-abstract-short" style="display: inline;"> Solar sources of suprathermal (<1 MeV/nucleon) 3He-rich solar energetic particles (SEPs) have been commonly associated with jets originating in small, compact active regions at the periphery of near-equatorial coronal holes. Sources of relatively rare, high-energy (>10 MeV/nucleon) 3He-rich SEPs remain unexplored. Here we present two of the most intense 3He-rich (3He/4He>1) SEP events of the curre… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.07735v1-abstract-full').style.display = 'inline'; document.getElementById('1812.07735v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1812.07735v1-abstract-full" style="display: none;"> Solar sources of suprathermal (<1 MeV/nucleon) 3He-rich solar energetic particles (SEPs) have been commonly associated with jets originating in small, compact active regions at the periphery of near-equatorial coronal holes. Sources of relatively rare, high-energy (>10 MeV/nucleon) 3He-rich SEPs remain unexplored. Here we present two of the most intense 3He-rich (3He/4He>1) SEP events of the current solar cycle 24 measured on the Advanced Composition Explorer at energy >10 MeV/nucleon. Although 3He shows high intensities, Z>2 ions are below the detection threshold. The events are accompanied by type-III radio bursts, but no type-II emission as typically seen for suprathermal 3He-rich SEPs. The corresponding solar sources were analyzed using high-resolution, extreme-ultraviolet imaging and photospheric magnetic field observations on the Solar Dynamics Observatory. We find the sources of these events associated with jets originating at the boundary of large sunspots with complex beta-gamma-delta magnetic configuration. Thus, details of the underlying photospheric field apparently are important to produce 3He to high energies in the examined events. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.07735v1-abstract-full').style.display = 'none'; document.getElementById('1812.07735v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 December, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJL 869, L21 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1807.09847">arXiv:1807.09847</a> <span> [<a href="https://arxiv.org/pdf/1807.09847">pdf</a>, <a href="https://arxiv.org/format/1807.09847">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/aad77b">10.3847/2041-8213/aad77b <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Truly Global Extreme Ultraviolet Wave from the SOL2017-09-10 X8.2+ Solar Flare-Coronal Mass Ejection </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Liu%2C+W">Wei Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Jin%2C+M">Meng Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Downs%2C+C">Cooper Downs</a>, <a href="/search/astro-ph?searchtype=author&query=Ofman%2C+L">Leon Ofman</a>, <a href="/search/astro-ph?searchtype=author&query=Cheung%2C+M+C+M">Mark C. M. Cheung</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1807.09847v2-abstract-short" style="display: inline;"> We report SDO/AIA observations of an extraordinary global extreme ultraviolet (EUV) wave triggered by the X8.2+ flare-CME eruption on 2017 September 10. This was one of the best EUV waves ever observed with modern instruments, yet it was likely the last one of such magnitudes of Solar Cycle 24 as the Sun heads toward the minimum. Its remarkable characteristics include the following. (1) The wave w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.09847v2-abstract-full').style.display = 'inline'; document.getElementById('1807.09847v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1807.09847v2-abstract-full" style="display: none;"> We report SDO/AIA observations of an extraordinary global extreme ultraviolet (EUV) wave triggered by the X8.2+ flare-CME eruption on 2017 September 10. This was one of the best EUV waves ever observed with modern instruments, yet it was likely the last one of such magnitudes of Solar Cycle 24 as the Sun heads toward the minimum. Its remarkable characteristics include the following. (1) The wave was observed, for the first time, to traverse the full-Sun corona over the entire visible solar disk and off-limb circumference, manifesting a truly global nature, owing to its exceptionally large amplitude, e.g., with EUV enhancements by up to 300% at 1.1 Rsun from the eruption. (2) This leads to strong transmissions (in addition to commonly observed reflections) in and out of both polar coronal holes, which are usually devoid of EUV waves. It has elevated wave speeds >2000 km/s within them, consistent with the expected higher fast-mode magnetosonic wave speeds. The coronal holes essentially serve as new "radiation centers" for the waves being refracted out of them, which then travel toward the equator and collide head-on, causing additional EUV enhancements. (3) The wave produces significant compressional heating to local plasma upon its impact, indicated by long-lasting EUV intensity changes and differential emission measure increases at higher temperatures (e.g., log T=6.2) accompanied by decreases at lower temperatures (e.g., log T=6.0). These characteristics signify the potential of such EUV waves for novel magnetic and thermal diagnostics of the solar corona {\it on global scales}. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.09847v2-abstract-full').style.display = 'none'; document.getElementById('1807.09847v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 August, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 July, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted by ApJ Letters (as of July 24, 2018), 8 pages, 5 figures; Update: minor edits made on August 14, 2018, after submitting ApJL proof corrections</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1807.01427">arXiv:1807.01427</a> <span> [<a href="https://arxiv.org/pdf/1807.01427">pdf</a>, <a href="https://arxiv.org/format/1807.01427">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/aae1fd">10.3847/1538-4357/aae1fd <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the Puzzle of Behind-the-Limb $纬$-ray Flares: Data-driven Simulations of Magnetic Connectivity and CME-driven Shock Evolution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Jin%2C+M">Meng Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Petrosian%2C+V">Vahe Petrosian</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+W">Wei Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Omodei%2C+N">Nicola Omodei</a>, <a href="/search/astro-ph?searchtype=author&query=da+Costa%2C+F+R">Fatima Rubio da Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Effenberger%2C+F">Frederic Effenberger</a>, <a href="/search/astro-ph?searchtype=author&query=Li%2C+G">Gang Li</a>, <a href="/search/astro-ph?searchtype=author&query=Pesce-Rollins%2C+M">Melissa Pesce-Rollins</a>, <a href="/search/astro-ph?searchtype=author&query=Allafort%2C+A">Alice Allafort</a>, <a href="/search/astro-ph?searchtype=author&query=Manchester%2C+W">Ward Manchester IV</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1807.01427v2-abstract-short" style="display: inline;"> Recent detections of high-energy $纬$-rays from behind-the-limb (BTL) solar flares by the \emph{Fermi $纬$-ray Space Telescope} pose a puzzle and challenge on the particle acceleration and transport mechanisms. In such events, the $纬$-ray emission region is located away from the BTL flare site by up to tens of degrees in heliogrpahic longitude. It is thus hypothesized that particles are accelerated… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.01427v2-abstract-full').style.display = 'inline'; document.getElementById('1807.01427v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1807.01427v2-abstract-full" style="display: none;"> Recent detections of high-energy $纬$-rays from behind-the-limb (BTL) solar flares by the \emph{Fermi $纬$-ray Space Telescope} pose a puzzle and challenge on the particle acceleration and transport mechanisms. In such events, the $纬$-ray emission region is located away from the BTL flare site by up to tens of degrees in heliogrpahic longitude. It is thus hypothesized that particles are accelerated at the shock driven by the coronal mass ejection (CME) and then travel from the shock downstream back to the front side of the Sun to produce the observed $纬$-rays. To test this scenario, we performed data-driven, global magnetohydrodynamics simulations of the CME associated with a well-observed BTL flare on 2014 September 1. We found that part of the CME-driven shock develops magnetic connectivity with the $纬$-ray emission region, facilitating transport of particles back to the Sun. Moreover, the observed increase in $纬$-ray flux is temporally correlated with (1) the increase of the shock compression ratio and (2) the presence of a quasi-perpendicular shock over the area that is magnetically connected to the $纬$-ray emitting region, both conditions favoring the diffusive shock acceleration (DSA) of particles. These results support the above hypothesis and can help resolve another puzzle, i.e., long-duration (up to 20 hours) $纬$-rays flares. We suggest that, in addition to DSA, stochastic acceleration by plasma turbulence may also play a role, especially in the shock downstream region and during the early stage when the shock Alfv茅n Mach number is small. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.01427v2-abstract-full').style.display = 'none'; document.getElementById('1807.01427v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 September, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 3 July, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">29 pages, 8 figures, accepted by ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1711.09394">arXiv:1711.09394</a> <span> [<a href="https://arxiv.org/pdf/1711.09394">pdf</a>, <a href="https://arxiv.org/ps/1711.09394">ps</a>, <a href="https://arxiv.org/format/1711.09394">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/aa9d8f">10.3847/1538-4357/aa9d8f <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> 3He-Rich Solar Energetic Particles in Helical Jets on the Sun </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bucik%2C+R">Radoslav Bucik</a>, <a href="/search/astro-ph?searchtype=author&query=Innes%2C+D+E">Davina E. Innes</a>, <a href="/search/astro-ph?searchtype=author&query=Mason%2C+G+M">Glenn M. Mason</a>, <a href="/search/astro-ph?searchtype=author&query=Wiedenbeck%2C+M+E">Mark E. Wiedenbeck</a>, <a href="/search/astro-ph?searchtype=author&query=Gomez-Herrero%2C+R">Raul Gomez-Herrero</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1711.09394v1-abstract-short" style="display: inline;"> Particle acceleration in stellar flares is ubiquitous in the Universe, however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of ten thousand) rare elements like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1711.09394v1-abstract-full').style.display = 'inline'; document.getElementById('1711.09394v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1711.09394v1-abstract-full" style="display: none;"> Particle acceleration in stellar flares is ubiquitous in the Universe, however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of ten thousand) rare elements like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense 3He- and Fe-rich solar energetic particle events ever reported. The events were accompanied by non-relativistic electron events and type III radio bursts. The corresponding high-resolution, extreme-ultraviolet imaging observations have revealed for the first time a helical structure in the source flare with a jet-like shape. The helical jets originated in relatively small, compact active regions, located at the coronal hole boundary. A mini-filament at the base of the jet appears to trigger these events. The events were observed with the two Solar Terrestrial Relations Observatories STEREO on the backside of the Sun, during the period of increased solar activity in 2014. The helical jets may be a distinct feature of these intense events that is related to the production of high 3He and Fe enrichments. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1711.09394v1-abstract-full').style.display = 'none'; document.getElementById('1711.09394v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 November, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">accepted for publication in The Astrophysical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.04900">arXiv:1603.04900</a> <span> [<a href="https://arxiv.org/pdf/1603.04900">pdf</a>, <a href="https://arxiv.org/format/1603.04900">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/0004-637X/820/1/16">10.3847/0004-637X/820/1/16 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Numerical Study of Long-Range Magnetic Impacts during Coronal Mass Ejections </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Jin%2C+M">M. Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Schrijver%2C+C+J">C. J. Schrijver</a>, <a href="/search/astro-ph?searchtype=author&query=Cheung%2C+M+C+M">M. C. M. Cheung</a>, <a href="/search/astro-ph?searchtype=author&query=DeRosa%2C+M+L">M. L. DeRosa</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Title%2C+A+M">A. M. Title</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1603.04900v1-abstract-short" style="display: inline;"> With the global view and high-cadence observations from SDO/AIA and STEREO, many spatially separated solar eruptive events appear to be coupled. However, the mechanisms for "sympathetic" events are still largely unknown. In this study, we investigate the impact of an erupting flux rope on surrounding solar structures through large-scale magnetic coupling. We build a realistic environment of the so… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.04900v1-abstract-full').style.display = 'inline'; document.getElementById('1603.04900v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.04900v1-abstract-full" style="display: none;"> With the global view and high-cadence observations from SDO/AIA and STEREO, many spatially separated solar eruptive events appear to be coupled. However, the mechanisms for "sympathetic" events are still largely unknown. In this study, we investigate the impact of an erupting flux rope on surrounding solar structures through large-scale magnetic coupling. We build a realistic environment of the solar corona on 2011 February 15 using a global magnetohydrodynamics (MHD) model and initiate coronal mass ejections (CMEs) in active region (AR) 11158 by inserting Gibson-Low analytical flux ropes. We show that a CME's impact on the surrounding structures depends not only on the magnetic strength of these structures and their distance to the source region, but also on the interaction between the CME with the large-scale magnetic field. Within the CME expansion domain where the flux rope field directly interacts with the solar structures, expansion-induced reconnection often modifies the overlying field, thereby increasing the decay index. This effect may provide a primary coupling mechanism underlying the sympathetic eruptions. The magnitude of the impact is found to depend on the orientation of the erupting flux rope, with the largest impacts occurring when the flux rope is favorably oriented for reconnecting with the surrounding regions. Outside the CME expansion domain, the influence of the CME is mainly through field line compression or post-eruption relaxation. Based on our numerical experiments, we discuss a way to quantify the eruption impact, which could be useful for forecasting purposes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.04900v1-abstract-full').style.display = 'none'; document.getElementById('1603.04900v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">38 pages, 13 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, Volume 820, Issue 1, article id. 16, 2016 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.03258">arXiv:1603.03258</a> <span> [<a href="https://arxiv.org/pdf/1603.03258">pdf</a>, <a href="https://arxiv.org/format/1603.03258">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1002/asna.201612428">10.1002/asna.201612428 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Observations of solar X-ray and EUV jets and their related phenomena </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Innes%2C+D">Davina Innes</a>, <a href="/search/astro-ph?searchtype=author&query=Bucik%2C+R">Radoslav Bucik</a>, <a href="/search/astro-ph?searchtype=author&query=Guo%2C+L">Li-Jia Guo</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1603.03258v2-abstract-short" style="display: inline;"> Solar jets are fast-moving, elongated brightenings related to ejections seen in both images and spectra on all scales from barely visible chromospheric jets to coronal jets extending up to a few solar radii. The largest, most powerful jets are the source of type III radio bursts, energetic electrons and ions with greatly enhanced $^3$He and heavy element abundances. The frequent coronal jets from… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.03258v2-abstract-full').style.display = 'inline'; document.getElementById('1603.03258v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.03258v2-abstract-full" style="display: none;"> Solar jets are fast-moving, elongated brightenings related to ejections seen in both images and spectra on all scales from barely visible chromospheric jets to coronal jets extending up to a few solar radii. The largest, most powerful jets are the source of type III radio bursts, energetic electrons and ions with greatly enhanced $^3$He and heavy element abundances. The frequent coronal jets from polar and equatorial coronal holes may contribute to the solar wind. The primary acceleration mechanism for all jets is believed to be release of magnetic stress via reconnection; however the energy buildup depends on the jets' source environment. In this review, we discuss how certain features of X-ray and EUV jets, such as their repetition rate and association with radio emission, depends on their underlying photospheric field configurations (active regions, polar and equatorial coronal holes, and quiet Sun). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.03258v2-abstract-full').style.display = 'none'; document.getElementById('1603.03258v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">(9 Pages, 8 Figures, Presented at 12th Potsdam Thinkshop "The Dynamic Sun - Exploring the Many Facets of Solar Eruptive Events". To be published in Astronomische Nachrichten</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1505.06804">arXiv:1505.06804</a> <span> [<a href="https://arxiv.org/pdf/1505.06804">pdf</a>, <a href="https://arxiv.org/ps/1505.06804">ps</a>, <a href="https://arxiv.org/format/1505.06804">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> Solar Sources of $^{3}$He-rich Solar Energetic Particle Events in Solar Cycle 24 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Mason%2C+G+M">Glenn M. Mason</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+L">Linghua Wang</a>, <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+C+M+S">Christina M. S. Cohen</a>, <a href="/search/astro-ph?searchtype=author&query=Wiedenbeck%2C+M+E">Mark E. Wiedenbeck</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1505.06804v1-abstract-short" style="display: inline;"> Using high-cadence extreme-ultraviolet (EUV) images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we investigate the solar sources of 26 $^{3}$He-rich solar energetic particle (SEP) events at $\lesssim$1 MeV nucleon$^{-1}$ that were well-observed by the Advanced Composition Explorer during solar cycle 24. Identification of the solar sources is based on… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1505.06804v1-abstract-full').style.display = 'inline'; document.getElementById('1505.06804v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1505.06804v1-abstract-full" style="display: none;"> Using high-cadence extreme-ultraviolet (EUV) images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we investigate the solar sources of 26 $^{3}$He-rich solar energetic particle (SEP) events at $\lesssim$1 MeV nucleon$^{-1}$ that were well-observed by the Advanced Composition Explorer during solar cycle 24. Identification of the solar sources is based on the association of $^{3}$He-rich events with type III radio bursts and electron events as observed by Wind. The source locations are further verified in EUV images from the Solar and Terrestrial Relations Observatory, which provides information on solar activities in the regions not visible from the Earth. Based on AIA observations, $^{3}$He-rich events are not only associated with coronal jets as emphasized in solar cycle 23 studies, but also with more spatially extended eruptions. The properties of the $^{3}$He-rich events do not appear to be strongly correlated with those of the source regions. As in the previous studies, the magnetic connection between the source region and the observer is not always reproduced adequately by the simple potential field source surface model combined with the Parker spiral. Instead, we find a broad longitudinal distribution of the source regions extending well beyond the west limb, with the longitude deviating significantly from that expected from the observed solar wind speed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1505.06804v1-abstract-full').style.display = 'none'; document.getElementById('1505.06804v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 May, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2015. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 10 figures, Astrophysical Journal, Accepted</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1411.6559">arXiv:1411.6559</a> <span> [<a href="https://arxiv.org/pdf/1411.6559">pdf</a>, <a href="https://arxiv.org/format/1411.6559">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s11207-014-0642-3">10.1007/s11207-014-0642-3 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Interplanetary Propagation Behavior of the Fast Coronal Mass Ejection from 23 July 2012 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Temmer%2C+M">Manuela Temmer</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1411.6559v1-abstract-short" style="display: inline;"> The fast coronal mass ejection (CME) from 23 July 2012 raised attention due to its extremely short transit time from Sun to 1 AU of less than 21 h. In-situ data from STEREO-A revealed the arrival of a fast forward shock with a speed of more than 2200 km s$^{-1}$ followed by a magnetic structure moving with almost 1900 km s$^{-1}$. We investigate the propagation behavior of the CME shock and magnet… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1411.6559v1-abstract-full').style.display = 'inline'; document.getElementById('1411.6559v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1411.6559v1-abstract-full" style="display: none;"> The fast coronal mass ejection (CME) from 23 July 2012 raised attention due to its extremely short transit time from Sun to 1 AU of less than 21 h. In-situ data from STEREO-A revealed the arrival of a fast forward shock with a speed of more than 2200 km s$^{-1}$ followed by a magnetic structure moving with almost 1900 km s$^{-1}$. We investigate the propagation behavior of the CME shock and magnetic structure with the aim to reproduce the short transit time and high impact speed as derived from in-situ data. We carefully measure the 3D kinematics of the CME using the graduated cylindrical shell model, and obtain a maximum speed of 2580$\pm$280 km s$^{-1}$ for the CME shock and of 2270$\pm$420 km s$^{-1}$ for its magnetic structure. Based on the 3D kinematics, the drag-based model (DBM) reproduces the observational data reasonably well. To successfully simulate the CME shock, we find that the ambient flow speed should be of average value close to the slow solar wind speed (450 km s$^{-1}$), and the initial shock speed at a distance of 30 $R_{\odot}$ should not exceed $\approx$2300 km s$^{-1}$, otherwise it would arrive much too early at STEREO-A. The model results indicate that an extremely low aerodynamic drag force is exerted on the shock, smaller by one order of magnitude compared to the average. As a consequence, the CME hardly decelerates in interplanetary space and maintains its high initial speed. The low aerodynamic drag can only be reproduced when reducing the density of the ambient solar wind flow, in which the massive CME propagates, to $蟻_{\rm sw}$=1-2 cm$^{-3}$ at the distance of 1 AU. This result is consistent with the preconditioning of interplanetary space owing to a previous CME. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1411.6559v1-abstract-full').style.display = 'none'; document.getElementById('1411.6559v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 November, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2014. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">in press for Solar Physics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1409.4754">arXiv:1409.4754</a> <span> [<a href="https://arxiv.org/pdf/1409.4754">pdf</a>, <a href="https://arxiv.org/format/1409.4754">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s11207-014-0602-y">10.1007/s11207-014-0602-y <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Relation Between Large-Scale Coronal Propagating Fronts and Type II Radio Bursts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+W">Wei Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Gopalswamy%2C+N">Nat Gopalswamy</a>, <a href="/search/astro-ph?searchtype=author&query=Yashiro%2C+S">Seiji Yashiro</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1409.4754v1-abstract-short" style="display: inline;"> Large-scale, wave-like disturbances in extreme-ultraviolet (EUV) and type II radio bursts are often associated with coronal mass ejections (CMEs). Both phenomena may signify shock waves driven by CMEs. Taking EUV full-disk images at an unprecedented cadence, the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory has observed the so-called EIT waves or large-scale coronal pro… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1409.4754v1-abstract-full').style.display = 'inline'; document.getElementById('1409.4754v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1409.4754v1-abstract-full" style="display: none;"> Large-scale, wave-like disturbances in extreme-ultraviolet (EUV) and type II radio bursts are often associated with coronal mass ejections (CMEs). Both phenomena may signify shock waves driven by CMEs. Taking EUV full-disk images at an unprecedented cadence, the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory has observed the so-called EIT waves or large-scale coronal propagating fronts (LCPFs) from their early evolution, which coincides with the period when most metric type II bursts occur. This article discusses the relation of LCPFs as captured by AIA with metric type II bursts. We show examples of type II bursts without a clear LCPF and fast LCPFs without a type II burst. Part of the disconnect between the two phenomena may be due to the difficulty in identifying them objectively. Furthermore, it is possible that the individual LCPFs and type II bursts may reflect different physical processes and external factors. In particular, the type II bursts that start at low frequencies and high altitudes tend to accompany an extended arc- shaped feature, which probably represents the 3D structure of the CME and the shock wave around it, rather than its near-surface track, which has usually been identified with EIT waves. This feature expands and propagates toward and beyond the limb. These events may be characterized by stretching of field lines in the radial direction, and be distinct from other LCPFs, which may be explained in terms of sudden lateral expansion of the coronal volume. Neither LCPFs nor type II bursts by themselves serve as necessary conditions for coronal shock waves, but these phenomena may provide useful information on the early evolution of the shock waves in 3D when both are clearly identified in eruptive events. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1409.4754v1-abstract-full').style.display = 'none'; document.getElementById('1409.4754v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 September, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2014. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 9 figures, accepted for publication in Solar Physics. Here, it became 24 pages long, but the original PDF file is available at bit.ly/1m0401J</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1405.6088">arXiv:1405.6088</a> <span> [<a href="https://arxiv.org/pdf/1405.6088">pdf</a>, <a href="https://arxiv.org/ps/1405.6088">ps</a>, <a href="https://arxiv.org/format/1405.6088">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/ncomms4481">10.1038/ncomms4481 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Observations of an extreme storm in interplanetary space caused by successive coronal mass ejections </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Liu%2C+Y+D">Ying D. Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Luhmann%2C+J+G">Janet G. Luhmann</a>, <a href="/search/astro-ph?searchtype=author&query=Kajdi%C4%8D%2C+P">Primo啪 Kajdi膷</a>, <a href="/search/astro-ph?searchtype=author&query=Kilpua%2C+E+K+J">Emilia K. J. Kilpua</a>, <a href="/search/astro-ph?searchtype=author&query=Lugaz%2C+N">No茅 Lugaz</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%B6stl%2C+C">Christian M枚stl</a>, <a href="/search/astro-ph?searchtype=author&query=Lavraud%2C+B">Benoit Lavraud</a>, <a href="/search/astro-ph?searchtype=author&query=Bale%2C+S+D">Stuart D. Bale</a>, <a href="/search/astro-ph?searchtype=author&query=Farrugia%2C+C+J">Charles J. Farrugia</a>, <a href="/search/astro-ph?searchtype=author&query=Galvin%2C+A+B">Antoinette B. Galvin</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1405.6088v1-abstract-short" style="display: inline;"> Space weather refers to dynamic conditions on the Sun and in the space environment of the Earth, which are often driven by solar eruptions and their subsequent interplanetary disturbances. It has been unclear how an extreme space weather storm forms and how severe it can be. Here we report and investigate an extreme event with multi-point remote-sensing and in-situ observations. The formation of t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1405.6088v1-abstract-full').style.display = 'inline'; document.getElementById('1405.6088v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1405.6088v1-abstract-full" style="display: none;"> Space weather refers to dynamic conditions on the Sun and in the space environment of the Earth, which are often driven by solar eruptions and their subsequent interplanetary disturbances. It has been unclear how an extreme space weather storm forms and how severe it can be. Here we report and investigate an extreme event with multi-point remote-sensing and in-situ observations. The formation of the extreme storm showed striking novel features. We suggest that the in-transit interaction between two closely launched coronal mass ejections resulted in the extreme enhancement of the ejecta magnetic field observed near 1 AU at STEREO A. The fast transit to STEREO A (in only 18.6 hours), or the unusually weak deceleration of the event, was caused by the preconditioning of the upstream solar wind by an earlier solar eruption. These results provide a new view crucial to solar physics and space weather as to how an extreme space weather event can arise from a combination of solar eruptions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1405.6088v1-abstract-full').style.display = 'none'; document.getElementById('1405.6088v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 May, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2014. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">23 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Communications, Volume 5, id. 3481 (2014) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1310.6029">arXiv:1310.6029</a> <span> [<a href="https://arxiv.org/pdf/1310.6029">pdf</a>, <a href="https://arxiv.org/format/1310.6029">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stt2032">10.1093/mnras/stt2032 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multi-wavelength Diagnostics of the Precursor and Main phases of an M1.8 Flare on 2011 April 22 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Awasthi%2C+A+K">A. K. Awasthi</a>, <a href="/search/astro-ph?searchtype=author&query=Jain%2C+R">R. Jain</a>, <a href="/search/astro-ph?searchtype=author&query=Gadhiya%2C+P+D">P. D. Gadhiya</a>, <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">M. J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Uddin%2C+W">W. Uddin</a>, <a href="/search/astro-ph?searchtype=author&query=Srivastava%2C+A+K">A. K. Srivastava</a>, <a href="/search/astro-ph?searchtype=author&query=Chandra%2C+R">R. Chandra</a>, <a href="/search/astro-ph?searchtype=author&query=Gopalswamy%2C+N">N. Gopalswamy</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">N. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Yashiro%2C+S">S. Yashiro</a>, <a href="/search/astro-ph?searchtype=author&query=Manoharan%2C+P+K">P. K. Manoharan</a>, <a href="/search/astro-ph?searchtype=author&query=Choudhary%2C+D+P">D. P. Choudhary</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+N+C">N. C. Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Dwivedi%2C+V+C">V. C. Dwivedi</a>, <a href="/search/astro-ph?searchtype=author&query=Mahalakshmi%2C+K">K. Mahalakshmi</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1310.6029v1-abstract-short" style="display: inline;"> We study the temporal, spatial and spectral evolution of the M1.8 flare, which occurred in NOAA AR 11195 (S17E31) on 22 April 2011, and explore the underlying physical processes during the precursors and their relation to the main phase. The study of the source morphology using the composite images in 131 掳A wavelength observed by the SDO/AIA and 6-14 keV revealed a multiloop system that destabili… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.6029v1-abstract-full').style.display = 'inline'; document.getElementById('1310.6029v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1310.6029v1-abstract-full" style="display: none;"> We study the temporal, spatial and spectral evolution of the M1.8 flare, which occurred in NOAA AR 11195 (S17E31) on 22 April 2011, and explore the underlying physical processes during the precursors and their relation to the main phase. The study of the source morphology using the composite images in 131 掳A wavelength observed by the SDO/AIA and 6-14 keV revealed a multiloop system that destabilized systematically during the precursor and main phases. In contrast, HXR emission (20-50 keV) was absent during the precursor phase, appearing only from the onset of the impulsive phase in the form of foot-points of emitting loop/s. This study has also revealed the heated loop-top prior to the loop emission, although no accompanying foot-point sources were observed during the precursor phase. We estimate the flare plasma parameters viz. T, EM, power-law index, and photon turn-over energy by forward fitting RHESSI spectral observations. The energy released in the precursor phase was thermal and constituted ~1 per cent of the total energy released during the flare. The study of morphological evolution of the filament in conjunction with synthesized T and EM maps has been carried out which reveals (a) Partial filament eruption prior to the onset of the precursor emission, (b) Heated dense plasma over the polarity inversion line and in the vicinity of the slowly rising filament during the precursor phase. Based on the implications from multi-wavelength observations, we propose a scheme to unify the energy release during the precursor and main phase emissions in which, the precursor phase emission has been originated via conduction front formed due to the partial filament eruption. Next, the heated leftover S-shaped filament has undergone slow rise and heating due to magnetic reconnection and finally erupted to produce emission during the impulsive and gradual phases. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.6029v1-abstract-full').style.display = 'none'; document.getElementById('1310.6029v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 October, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 Pages, 11 Figures, Accepted for Publication in MNRAS Main Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1308.3544">arXiv:1308.3544</a> <span> [<a href="https://arxiv.org/pdf/1308.3544">pdf</a>, <a href="https://arxiv.org/ps/1308.3544">ps</a>, <a href="https://arxiv.org/format/1308.3544">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/776/1/58">10.1088/0004-637X/776/1/58 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Large-scale Coronal Propagating Fronts in Solar Eruptions as Observed by the Atmospheric Imaging Assembly on Board the Solar Dynamics Observatory\,--\,An Ensemble Study </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Schrijver%2C+C+J">Carolus J. Schrijver</a>, <a href="/search/astro-ph?searchtype=author&query=Title%2C+A+M">Alan M. Title</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+W">Wei Liu</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1308.3544v1-abstract-short" style="display: inline;"> This paper presents a study of a large sample of global disturbances in the solar corona with characteristic propagating fronts as intensity enhancement, similar to the phenomena that have often been referred to as EIT waves or EUV waves. Now Extreme Ultraviolet (EUV) images obtained by the {\it Atmospheric Imaging Assembly} (AIA) on board the {\it Solar Dynamics Observatory} (SDO) provide a signi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.3544v1-abstract-full').style.display = 'inline'; document.getElementById('1308.3544v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1308.3544v1-abstract-full" style="display: none;"> This paper presents a study of a large sample of global disturbances in the solar corona with characteristic propagating fronts as intensity enhancement, similar to the phenomena that have often been referred to as EIT waves or EUV waves. Now Extreme Ultraviolet (EUV) images obtained by the {\it Atmospheric Imaging Assembly} (AIA) on board the {\it Solar Dynamics Observatory} (SDO) provide a significantly improved view of these large-scale coronal propagating fronts (LCPFs). Between April 2010 and January 2013, a total of 171 LCPFs have been identified through visual inspection of AIA images in the 193 脜 channel. Here we focus on the 138 LCPFs that are seen to propagate across the solar disk, first studying how they are associated with flares, coronal mass ejections (CMEs) and type II radio bursts. We measure the speed of the LCPF in various directions until it is clearly altered by active regions or coronal holes. The highest speed is extracted for each LCPF. It is often considerably higher than EIT waves. We do not find a pattern where faster LCPFs decelerate and slow LCPFs accelerate. Furthermore, the speeds are not strongly correlated with the flare intensity or CME magnitude, nor do they show an association with type II bursts. We do not find a good correlation either between the speeds of LCPFs and CMEs in a subset of 86 LCPFs observed by one or both of the {\it Solar and Terrestrial Relations Observatory} (STEREO) spacecraft as limb events. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.3544v1-abstract-full').style.display = 'none'; document.getElementById('1308.3544v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 August, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">30 pages, 9 figures, accepted by the Astrophysical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1308.1465">arXiv:1308.1465</a> <span> [<a href="https://arxiv.org/pdf/1308.1465">pdf</a>, <a href="https://arxiv.org/ps/1308.1465">ps</a>, <a href="https://arxiv.org/format/1308.1465">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s11207-013-0388-3">10.1007/s11207-013-0388-3 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Association of Solar Flares with Coronal Mass Ejections During the Extended Solar Minimum </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">M. J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Freeland%2C+S+L">S. L. Freeland</a>, <a href="/search/astro-ph?searchtype=author&query=Lemen%2C+J+R">J. R. Lemen</a>, <a href="/search/astro-ph?searchtype=author&query=W%C3%BClser%2C+J+-">J. -P. W眉lser</a>, <a href="/search/astro-ph?searchtype=author&query=Zarro%2C+D+M">D. M. Zarro</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1308.1465v1-abstract-short" style="display: inline;"> We study the association of solar flares with coronal mass ejections (CMEs) during the deep, extended solar minimum of 2007-2009, using extreme-ultraviolet (EUV) and white-light (coronagraph) images from the {\it Solar Terrestrial Relations Observatory} (STEREO). Although all of the fast (v $>$ 900 km s$^{-1}$) {\it and} wide ($胃>$ 100$\arcdeg$) CMEs are associated with a flare that is at least id… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.1465v1-abstract-full').style.display = 'inline'; document.getElementById('1308.1465v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1308.1465v1-abstract-full" style="display: none;"> We study the association of solar flares with coronal mass ejections (CMEs) during the deep, extended solar minimum of 2007-2009, using extreme-ultraviolet (EUV) and white-light (coronagraph) images from the {\it Solar Terrestrial Relations Observatory} (STEREO). Although all of the fast (v $>$ 900 km s$^{-1}$) {\it and} wide ($胃>$ 100$\arcdeg$) CMEs are associated with a flare that is at least identified in GOES soft X-ray light curves, a majority of flares with relatively high X-ray intensity for the deep solar minimum (e.g. $\gtrsim$1 \times 10^{-6}$ W m$^{-2}$ or C1) are not associated with CMEs. Intense flares tend to occur in active regions with strong and complex photospheric magnetic field, but the active regions that produce CME-associated flares tend to be small, including those that have no sunspots and therefore no NOAA active-region numbers. Other factors on scales comparable to and larger than active regions seem to exist that contribute to the association of flares with CMEs. We find the possible low coronal signatures of CMEs, namely eruptions, dimmings, EUV waves, and Type III bursts, in 91%, 74%, 57%, and 74%, respectively, of the 35 flares that we associate with CMEs. None of these observables can fully replace direct observations of CMEs by coronagraphs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.1465v1-abstract-full').style.display = 'none'; document.getElementById('1308.1465v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 August, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages, 9 figures, accepted by Solar Physics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1304.4163">arXiv:1304.4163</a> <span> [<a href="https://arxiv.org/pdf/1304.4163">pdf</a>, <a href="https://arxiv.org/ps/1304.4163">ps</a>, <a href="https://arxiv.org/format/1304.4163">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s11207-013-0307-7">10.1007/s11207-013-0307-7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Soft X-ray Fluxes of Major Flares Far Behind the Limb as Estimated Using STEREO EUV Images </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">M. J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Boerner%2C+P+F">P. F. Boerner</a>, <a href="/search/astro-ph?searchtype=author&query=Freeland%2C+S+L">S. L. Freeland</a>, <a href="/search/astro-ph?searchtype=author&query=Lemen%2C+J+R">J. R. Lemen</a>, <a href="/search/astro-ph?searchtype=author&query=Wuelser%2C+J+-">J. -P. Wuelser</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1304.4163v1-abstract-short" style="display: inline;"> With increasing solar activity since 2010, many flares from the backside of the Sun have been observed by the Extreme Ultraviolet Imager (EUVI) on either of the twin STEREO spacecraft. Our objective is to estimate their X-ray peak fluxes from EUVI data by finding a relation of the EUVI with GOES X-ray fluxes. Because of the presence of the Fe xxiv line at 192 A, the response of the EUVI 195 A chan… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1304.4163v1-abstract-full').style.display = 'inline'; document.getElementById('1304.4163v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1304.4163v1-abstract-full" style="display: none;"> With increasing solar activity since 2010, many flares from the backside of the Sun have been observed by the Extreme Ultraviolet Imager (EUVI) on either of the twin STEREO spacecraft. Our objective is to estimate their X-ray peak fluxes from EUVI data by finding a relation of the EUVI with GOES X-ray fluxes. Because of the presence of the Fe xxiv line at 192 A, the response of the EUVI 195 A channel has a secondary broad peak around 15 MK, and its fluxes closely trace X-ray fluxes during the rise phase of flares. If the flare plasma is isothermal, the EUVI flux should be directly proportional to the GOES flux. In reality, the multithermal nature of the flare and other factors complicate the estimation of the X-ray fluxes from EUVI observations. We discuss the uncer- tainties, by comparing GOES fluxes with the high cadence EUV data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We conclude that the EUVI 195 A data can provide estimates of the X-ray peak fluxes of intense flares (e.g., above M4 in the GOES scale) with uncertainties of a factor of a few. Lastly we show examples of intense flares from regions far behind the limb, some of which show eruptive signatures in AIA images. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1304.4163v1-abstract-full').style.display = 'none'; document.getElementById('1304.4163v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 April, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 9 figures, accepted by Solar Physics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1303.1251">arXiv:1303.1251</a> <span> [<a href="https://arxiv.org/pdf/1303.1251">pdf</a>, <a href="https://arxiv.org/ps/1303.1251">ps</a>, <a href="https://arxiv.org/format/1303.1251">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.asr.2013.03.009">10.1016/j.asr.2013.03.009 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Multiwavelength Study of Eruptive Events on January 23, 2012 Associated with a Major Solar Energetic Particle Event </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+N+C">N. C. Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Uddin%2C+W">W. Uddin</a>, <a href="/search/astro-ph?searchtype=author&query=Srivastava%2C+A+K">A. K. Srivastava</a>, <a href="/search/astro-ph?searchtype=author&query=Chandra%2C+R">R. Chandra</a>, <a href="/search/astro-ph?searchtype=author&query=Gopalswamy%2C+N">N. Gopalswamy</a>, <a href="/search/astro-ph?searchtype=author&query=Manoharan%2C+P+K">P. K. Manoharan</a>, <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">M. J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Choudhary%2C+D+P">D. P. Choudhary</a>, <a href="/search/astro-ph?searchtype=author&query=Jain%2C+R">R. Jain</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Xie%2C+H">H. Xie</a>, <a href="/search/astro-ph?searchtype=author&query=Yashiro%2C+S">S. Yashiro</a>, <a href="/search/astro-ph?searchtype=author&query=Akiyama%2C+S">S. Akiyama</a>, <a href="/search/astro-ph?searchtype=author&query=Makela%2C+P">P. Makela</a>, <a href="/search/astro-ph?searchtype=author&query=Kayshap%2C+P">P. Kayshap</a>, <a href="/search/astro-ph?searchtype=author&query=Awasthi%2C+A+K">A. K. Awasthi</a>, <a href="/search/astro-ph?searchtype=author&query=Dwivedi%2C+V+C">V. C. Dwivedi</a>, <a href="/search/astro-ph?searchtype=author&query=Mahalakshmi%2C+K">K. Mahalakshmi</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1303.1251v1-abstract-short" style="display: inline;"> We use multiwavelength data from space and ground based instruments to study the solar flares and coronal mass ejections (CMEs) on January 23, 2012 that were responsible for one of the largest solar energetic particle (SEP) events of solar cycle 24. The eruptions consisting of two fast CMEs (1400 km/s and 2000 km/s) and M-class flares that occurred in active region 11402 located at N28 W36. The tw… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.1251v1-abstract-full').style.display = 'inline'; document.getElementById('1303.1251v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1303.1251v1-abstract-full" style="display: none;"> We use multiwavelength data from space and ground based instruments to study the solar flares and coronal mass ejections (CMEs) on January 23, 2012 that were responsible for one of the largest solar energetic particle (SEP) events of solar cycle 24. The eruptions consisting of two fast CMEs (1400 km/s and 2000 km/s) and M-class flares that occurred in active region 11402 located at N28 W36. The two CMEs occurred in quick successions, so they interacted very close to the Sun. The second CME caught up with the first one at a distance of 11-12 Rsun. The CME interaction may be responsible for the elevated SEP flux and significant changes in the intensity profile of the SEP event. The compound CME resulted in a double-dip moderate geomagnetic storm (Dst = -73 nT). The two dips are due to the southward component of the interplanetary magnetic field in the shock sheath and the ICME intervals. One possible reason for the lack of a stronger geomagnetic storm may be that the ICME delivered a glancing blow to Earth. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.1251v1-abstract-full').style.display = 'none'; document.getElementById('1303.1251v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 March, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">29 pages, 11 figures, Accepted for publication in ADSPR</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1301.0893">arXiv:1301.0893</a> <span> [<a href="https://arxiv.org/pdf/1301.0893">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.asr.2013.01.006">10.1016/j.asr.2013.01.006 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Height of Shock Formation in the Solar Corona Inferred from Observations of Type II Radio Bursts and Coronal Mass Ejections </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gopalswamy%2C+N">N. Gopalswamy</a>, <a href="/search/astro-ph?searchtype=author&query=Xie%2C+H">H. Xie</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%A4kel%C3%A4%2C+P">P. M盲kel盲</a>, <a href="/search/astro-ph?searchtype=author&query=Yashiro%2C+S">S. Yashiro</a>, <a href="/search/astro-ph?searchtype=author&query=Akiyama%2C+S">S. Akiyama</a>, <a href="/search/astro-ph?searchtype=author&query=Srivastava%2C+W+U+A+K">W. Uddin. A. K. Srivastava</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+N+C">N. C. Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Chandra%2C+R">R. Chandra</a>, <a href="/search/astro-ph?searchtype=author&query=Manoharan%2C+P+K">P. K. Manoharan</a>, <a href="/search/astro-ph?searchtype=author&query=Mahalakshmi%2C+K">K. Mahalakshmi</a>, <a href="/search/astro-ph?searchtype=author&query=Dwivedi%2C+V+C">V. C. Dwivedi</a>, <a href="/search/astro-ph?searchtype=author&query=Awasthi%2C+R+J+A+K">R. Jain A. K. Awasthi</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">M. J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Choudhary%2C+D+P">D. P. Choudhary</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1301.0893v1-abstract-short" style="display: inline;"> Employing coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from sola… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1301.0893v1-abstract-full').style.display = 'inline'; document.getElementById('1301.0893v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1301.0893v1-abstract-full" style="display: none;"> Employing coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from solar cycle 24. We minimized the projection effects by making the measurements from a view that is roughly orthogonal to the direction of the ejection. We also chose image frames close to the onset times of the type II bursts, so no extrapolation was necessary. We found that the CMEs were located in the heliocentric distance range from 1.20 to 1.93 solar radii (Rs), with mean and median values of 1.43 and 1.38 Rs, respectively. We conclusively find that the shock formation can occur at heights substantially below 1.5 Rs. In a few cases, the CME height at type II onset was close to 2 Rs. In these cases, the starting frequency of the type II bursts was very low, in the range 25 to 40 MHz, which confirms that the shock can also form at larger heights. The starting frequencies of metric type II bursts have a weak correlation with the measured CME/shock heights and are consistent with the rapid decline of density with height in the inner corona. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1301.0893v1-abstract-full').style.display = 'none'; document.getElementById('1301.0893v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 January, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 4 figures, 2 tables, COSPAR 2012</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1209.2866">arXiv:1209.2866</a> <span> [<a href="https://arxiv.org/pdf/1209.2866">pdf</a>, <a href="https://arxiv.org/ps/1209.2866">ps</a>, <a href="https://arxiv.org/format/1209.2866">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/758/1/10">10.1088/0004-637X/758/1/10 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multi-point shock and flux rope analysis of multiple interplanetary coronal mass ejections around 2010 August 1 in the inner heliosphere </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=M%C3%B6stl%2C+C">C. M枚stl</a>, <a href="/search/astro-ph?searchtype=author&query=Farrugia%2C+C+J">C. J. Farrugia</a>, <a href="/search/astro-ph?searchtype=author&query=Kilpua%2C+E+K+J">E. K. J. Kilpua</a>, <a href="/search/astro-ph?searchtype=author&query=Jian%2C+L+K">L. K. Jian</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+Y">Y. Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Eastwood%2C+J">J. Eastwood</a>, <a href="/search/astro-ph?searchtype=author&query=Harrison%2C+R+A">R. A. Harrison</a>, <a href="/search/astro-ph?searchtype=author&query=Webb%2C+D+F">D. F. Webb</a>, <a href="/search/astro-ph?searchtype=author&query=Temmer%2C+M">M. Temmer</a>, <a href="/search/astro-ph?searchtype=author&query=Odstrcil%2C+D">D. Odstrcil</a>, <a href="/search/astro-ph?searchtype=author&query=Davies%2C+J+A">J. A. Davies</a>, <a href="/search/astro-ph?searchtype=author&query=Rollett%2C+T">T. Rollett</a>, <a href="/search/astro-ph?searchtype=author&query=Luhmann%2C+J+G">J. G. Luhmann</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">N. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Mulligan%2C+T">T. Mulligan</a>, <a href="/search/astro-ph?searchtype=author&query=Jensen%2C+E+A">E. A. Jensen</a>, <a href="/search/astro-ph?searchtype=author&query=Forsyth%2C+R">R. Forsyth</a>, <a href="/search/astro-ph?searchtype=author&query=Lavraud%2C+B">B. Lavraud</a>, <a href="/search/astro-ph?searchtype=author&query=De+Koning%2C+C+A">C. A. De Koning</a>, <a href="/search/astro-ph?searchtype=author&query=Veronig%2C+A+M">A. M. Veronig</a>, <a href="/search/astro-ph?searchtype=author&query=Galvin%2C+A+B">A. B. Galvin</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+T+L">T. L. Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+B+J">B. J. Anderson</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1209.2866v1-abstract-short" style="display: inline;"> We present multi-point in situ observations of a complex sequence of coronal mass ejections (CMEs) which may serve as a benchmark event for numerical and empirical space weather prediction models. On 2010 August 1, instruments on various space missions (Solar Dynamics Observatory/ Solar and Heliospheric Observatory/Solar-TErrestrial-RElations-Observatory) monitored several CMEs originating within… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1209.2866v1-abstract-full').style.display = 'inline'; document.getElementById('1209.2866v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1209.2866v1-abstract-full" style="display: none;"> We present multi-point in situ observations of a complex sequence of coronal mass ejections (CMEs) which may serve as a benchmark event for numerical and empirical space weather prediction models. On 2010 August 1, instruments on various space missions (Solar Dynamics Observatory/ Solar and Heliospheric Observatory/Solar-TErrestrial-RElations-Observatory) monitored several CMEs originating within tens of degrees from solar disk center. We compare their imprints on four widely separated locations, spanning 120 degree in heliospheric longitude, with radial distances from the Sun ranging from MESSENGER (0.38 AU) to Venus Express (VEX, at 0.72 AU) to Wind, ACE and ARTEMIS near Earth, and STEREO-B close to 1 AU. Calculating shock and flux rope parameters at each location points to a non-spherical shape of the shock, and shows the global configuration of the interplanetary coronal mass ejections (ICMEs), which have interacted, but do not seem to have merged. VEX and STEREO-B observed similar magnetic flux ropes (MFRs), in contrast to structures at Wind. The geomagnetic storm was intense, reaching two minima in the Dst index (~ -100 nT), caused by the sheath region behind the shock and one of two observed MFRs. MESSENGER received a glancing blow of the ICMEs, and the events missed STEREO-A entirely. The observations demonstrate how sympathetic solar eruptions may immerse at least 1/3 of the heliosphere in the ecliptic with their distinct plasma and magnetic field signatures. We also emphasize the difficulties in linking the local views derived from single-spacecraft observations to a consistent global picture, pointing to possible alterations from the classical picture of ICMEs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1209.2866v1-abstract-full').style.display = 'none'; document.getElementById('1209.2866v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 September, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 10 figures, 3 tables, accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1207.2790">arXiv:1207.2790</a> <span> [<a href="https://arxiv.org/pdf/1207.2790">pdf</a>, <a href="https://arxiv.org/ps/1207.2790">ps</a>, <a href="https://arxiv.org/format/1207.2790">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/756/2/124">10.1088/0004-637X/756/2/124 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> First 3D Reconstructions of Coronal Loops with the STEREO A+B Spacecraft: IV. Magnetic Modeling with Twisted Force-Free Fields </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">Markus J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Wuelser%2C+J">Jean-Pierre Wuelser</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Lemen%2C+J+R">James R. Lemen</a>, <a href="/search/astro-ph?searchtype=author&query=DeRosa%2C+M+L">Marc L. DeRosa</a>, <a href="/search/astro-ph?searchtype=author&query=Malanushenko%2C+A">Anna Malanushenko</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1207.2790v1-abstract-short" style="display: inline;"> The three-dimensional (3D) coordinates of stereoscopically triangulated loops provide strong constraints for magnetic field models of active regions in the solar corona. Here we use STEREO/A and B data from some 500 stereoscopically triangulated loops observed in four active regions (2007 Apr 30, May 9, May 19, Dec 11), together with SOHO/MDI line-of-sight magnetograms. We measure the average misa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1207.2790v1-abstract-full').style.display = 'inline'; document.getElementById('1207.2790v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1207.2790v1-abstract-full" style="display: none;"> The three-dimensional (3D) coordinates of stereoscopically triangulated loops provide strong constraints for magnetic field models of active regions in the solar corona. Here we use STEREO/A and B data from some 500 stereoscopically triangulated loops observed in four active regions (2007 Apr 30, May 9, May 19, Dec 11), together with SOHO/MDI line-of-sight magnetograms. We measure the average misalignment angle between the stereoscopic loops and theoretical magnetic field models, finding a mismatch of $渭=19^\circ-46^\circ$ for a potential field model, which is reduced to $渭=14^\circ-19^\circ$ for a non-potential field model parameterized by twist parameters. The residual error is commensurable with stereoscopic measurement errors ($渭_{SE} \approx 8^\circ-12^\circ$). We developed a potential field code that deconvolves a line-of-sight magnetogram into three magnetic field components $(B_x, B_y, B_z)$, as well as a non-potential field forward-fitting code that determines the full length of twisted loops ($L \approx 50-300$ Mm), the number of twist turns (median $N_{twist}=0.06$), the nonlinear force-free $伪$-parameter (median $伪\approx 4 \times 10^{-11}$ cm$^{-1}$), and the current density (median $j_z \approx 1500$ Mx cm$^{-2}$ s$^{-1}$). All twisted loops are found to be far below the critical value for kink instability, and Joule dissipation of their currents is found be be far below the coronal heating requirement. The algorithm developed here, based on an analytical solution of nonlinear force-free fields that is accurate to second order (in the force-free parameter $伪$), represents the first code that enables fast forward-fitting to photospheric magnetograms and stereoscopically triangulated loops in the solar corona. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1207.2790v1-abstract-full').style.display = 'none'; document.getElementById('1207.2790v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 July, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">The Astrophysical Journal (in press), 37 pages, 14 Figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1207.2787">arXiv:1207.2787</a> <span> [<a href="https://arxiv.org/pdf/1207.2787">pdf</a>, <a href="https://arxiv.org/ps/1207.2787">ps</a>, <a href="https://arxiv.org/format/1207.2787">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s11207-012-0092-8">10.1007/s11207-012-0092-8 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Solar Stereoscopy with STEREO/EUVI A and B spacecraft from small (6 deg) to large (170 deg) spacecraft separation angles </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">Markus J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=W%C3%BClser%2C+J">Jean-Pierre W眉lser</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Lemen%2C+J">James Lemen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1207.2787v1-abstract-short" style="display: inline;"> We performed for the first time stereoscopic triangulation of coronal loops in active regions over the entire range of spacecraft separation angles ($伪_{sep}\approx 6^\circ, 43^\circ, 89^\circ, 127^\circ$, and $170^\circ$). The accuracy of stereoscopic correlation depends mostly on the viewing angle with respect to the solar surface for each spacecraft, which affects the stereoscopic correspondenc… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1207.2787v1-abstract-full').style.display = 'inline'; document.getElementById('1207.2787v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1207.2787v1-abstract-full" style="display: none;"> We performed for the first time stereoscopic triangulation of coronal loops in active regions over the entire range of spacecraft separation angles ($伪_{sep}\approx 6^\circ, 43^\circ, 89^\circ, 127^\circ$, and $170^\circ$). The accuracy of stereoscopic correlation depends mostly on the viewing angle with respect to the solar surface for each spacecraft, which affects the stereoscopic correspondence identification of loops in image pairs. From a simple theoretical model we predict an optimum range of $伪_{sep} \approx 22^\circ-125^\circ$, which is also experimentally confirmed. The best accuracy is generally obtained when an active region passes the central meridian (viewed from Earth), which yields a symmetric view for both STEREO spacecraft and causes minimum horizontal foreshortening. For the extended angular range of $伪_{sep}\approx 6^\circ-127^{\circ}$ we find a mean 3D misalignment angle of $渭_{PF} \approx 21^\circ-39^\circ$ of stereoscopically triangulated loops with magnetic potential field models, and $渭_{FFF} \approx 15^\circ-21^\circ$ for a force-free field model, which is partly caused by stereoscopic uncertainties $渭_{SE} \approx 9^\circ$. We predict optimum conditions for solar stereoscopy during the time intervals of 2012--2014, 2016--2017, and 2021--2023. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1207.2787v1-abstract-full').style.display = 'none'; document.getElementById('1207.2787v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 July, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Solar Physics, (in press), 22 pages, 9 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1204.5470">arXiv:1204.5470</a> <span> [<a href="https://arxiv.org/pdf/1204.5470">pdf</a>, <a href="https://arxiv.org/ps/1204.5470">ps</a>, <a href="https://arxiv.org/format/1204.5470">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Plasma Physics">physics.plasm-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/753/1/52">10.1088/0004-637X/753/1/52 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quasi-periodic Fast-mode Wave Trains Within a Global EUV Wave and Sequential Transverse Oscillations Detected by SDO/AIA </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Liu%2C+W">Wei Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Ofman%2C+L">Leon Ofman</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">Markus J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Schrijver%2C+C+J">Carolus J. Schrijver</a>, <a href="/search/astro-ph?searchtype=author&query=Title%2C+A+M">Alan M. Title</a>, <a href="/search/astro-ph?searchtype=author&query=Tarbell%2C+T+D">Theodore D. Tarbell</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1204.5470v1-abstract-short" style="display: inline;"> We present the first unambiguous detection of quasi-periodic wave trains within the broad pulse of a global EUV wave (so-called "EIT wave") occurring on the limb. These wave trains, running ahead of the lateral CME front of 2-4 times slower, coherently travel to distances $>R_{sun}/2$ along the solar surface, with initial velocities up to 1400 km/s decelerating to ~650 km/s. The rapid expansion of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1204.5470v1-abstract-full').style.display = 'inline'; document.getElementById('1204.5470v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1204.5470v1-abstract-full" style="display: none;"> We present the first unambiguous detection of quasi-periodic wave trains within the broad pulse of a global EUV wave (so-called "EIT wave") occurring on the limb. These wave trains, running ahead of the lateral CME front of 2-4 times slower, coherently travel to distances $>R_{sun}/2$ along the solar surface, with initial velocities up to 1400 km/s decelerating to ~650 km/s. The rapid expansion of the CME initiated at an elevated height of 110 Mm produces a strong downward and lateral compression, which may play an important role in driving the primary EUV wave and shaping its front forwardly inclined toward the solar surface. The waves have a dominant 2 min periodicity that matches the X-ray flare pulsations, suggesting a causal connection. The arrival of the leading EUV wave front at increasing distances produces an uninterrupted chain sequence of deflections and/or transverse (likely fast kink mode) oscillations of local structures, including a flux-rope coronal cavity and its embedded filament with delayed onsets consistent with the wave travel time at an elevated (by ~50%) velocity within it. This suggests that the EUV wave penetrates through a topological separatrix surface into the cavity, unexpected from CME caused magnetic reconfiguration. These observations, when taken together, provide compelling evidence of the fast-mode MHD wave nature of the {\it primary (outer) fast component} of a global EUV wave, running ahead of the {\it secondary (inner) slow} component of CME-caused restructuring. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1204.5470v1-abstract-full').style.display = 'none'; document.getElementById('1204.5470v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 April, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">17 pages, 12 figures; accepted by ApJ, April 24, 2012</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, Volume 753, Issue 1, article id. 52 (07/2012) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1203.5777">arXiv:1203.5777</a> <span> [<a href="https://arxiv.org/pdf/1203.5777">pdf</a>, <a href="https://arxiv.org/format/1203.5777">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s11214-012-9877-1">10.1007/s11214-012-9877-1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> What Are Special About Ground-Level Events? Flares, CMEs, Active Regions And Magnetic Field Connection </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">N. V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+Y">Y. Liu</a>, <a href="/search/astro-ph?searchtype=author&query=DeRosa%2C+M+L">M. L. DeRosa</a>, <a href="/search/astro-ph?searchtype=author&query=Nightingale%2C+R+W">R. W. Nightingale</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1203.5777v1-abstract-short" style="display: inline;"> Ground level events (GLEs) occupy the high-energy end of gradual solar energetic particle (SEP) events. They are associated with coronal mass ejections (CMEs) and solar flares, but we still do not clearly understand the special conditions that produce these rare events. During Solar Cycle 23, a total of 16 GLEs were registered, using ground-based neutron monitor data. We first ask if these GLEs ar… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1203.5777v1-abstract-full').style.display = 'inline'; document.getElementById('1203.5777v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1203.5777v1-abstract-full" style="display: none;"> Ground level events (GLEs) occupy the high-energy end of gradual solar energetic particle (SEP) events. They are associated with coronal mass ejections (CMEs) and solar flares, but we still do not clearly understand the special conditions that produce these rare events. During Solar Cycle 23, a total of 16 GLEs were registered, using ground-based neutron monitor data. We first ask if these GLEs are clearly distinguishable from other SEP events observed from space. Setting aside possible difficulties in identifying all GLEs consistently, we then try to find observables which may unmistakably isolate these GLEs by studying the basic properties of the associated eruptions and the active regions (ARs) that produced them. It is found that neither the magnitudes of the CMEs and flares nor the complexities of the ARs give sufficient conditions for GLEs. It is possible to find CMEs, flares or ARs that are not associated with GLEs but that have more extreme properties than those associated with GLEs. We also try to evaluate the importance of magnetic field connection of the AR with Earth on the detection of GLEs and their onset times. Using the potential field source surface (PFSS) model, a half of the GLEs are found to be well-connected. However, the GLE onset time with respect to the onset of the associated flare and CME does not strongly depend on how well-connected the AR is. The GLE onset behavior may be largely determined by when and where the CME-driven shock develops. We could not relate the shocks responsible for the onsets of past GLEs with features in solar images, but the combined data from the Solar TErrestrial RElations Observatory (STEREO) and the Solar Dynamics Observatory (SDO) have the potential to change this for GLEs that may occur in the rising phase of Solar Cycle 24. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1203.5777v1-abstract-full').style.display = 'none'; document.getElementById('1203.5777v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 March, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">25 pages, 9 figures, accepted by Space Science Reviews</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1202.0629">arXiv:1202.0629</a> <span> [<a href="https://arxiv.org/pdf/1202.0629">pdf</a>, <a href="https://arxiv.org/format/1202.0629">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/749/1/57">10.1088/0004-637X/749/1/57 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Characteristics of kinematics of a coronal mass ejection during the 2010 August 1 CME-CME interaction event </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Temmer%2C+M">Manuela Temmer</a>, <a href="/search/astro-ph?searchtype=author&query=Vrsnak%2C+B">Bojan Vrsnak</a>, <a href="/search/astro-ph?searchtype=author&query=Rollett%2C+T">Tanja Rollett</a>, <a href="/search/astro-ph?searchtype=author&query=Bein%2C+B">Bianca Bein</a>, <a href="/search/astro-ph?searchtype=author&query=de+Koning%2C+C+A">Curt A. de Koning</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+Y">Ying Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Bosman%2C+E">Eckhard Bosman</a>, <a href="/search/astro-ph?searchtype=author&query=Davies%2C+J+A">Jackie A. Davies</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%B6stl%2C+C">Christian M枚stl</a>, <a href="/search/astro-ph?searchtype=author&query=Zic%2C+T">Tomislav Zic</a>, <a href="/search/astro-ph?searchtype=author&query=Veronig%2C+A+M">Astrid M. Veronig</a>, <a href="/search/astro-ph?searchtype=author&query=Bothmer%2C+V">Volker Bothmer</a>, <a href="/search/astro-ph?searchtype=author&query=Harrison%2C+R">Richard Harrison</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Bisi%2C+M">Mario Bisi</a>, <a href="/search/astro-ph?searchtype=author&query=Flor%2C+O">Olga Flor</a>, <a href="/search/astro-ph?searchtype=author&query=Eastwood%2C+J">Jonathan Eastwood</a>, <a href="/search/astro-ph?searchtype=author&query=Odstrcil%2C+D">Dusan Odstrcil</a>, <a href="/search/astro-ph?searchtype=author&query=Forsyth%2C+R">Robert Forsyth</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1202.0629v1-abstract-short" style="display: inline;"> We study the interaction of two successive coronal mass ejections (CMEs) during the 2010 August 1 events using STEREO/SECCHI COR and HI data. We obtain the direction of motion for both CMEs by applying several independent reconstruction methods and find that the CMEs head in similar directions. This provides evidence that a full interaction takes place between the two CMEs that can be observed in… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1202.0629v1-abstract-full').style.display = 'inline'; document.getElementById('1202.0629v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1202.0629v1-abstract-full" style="display: none;"> We study the interaction of two successive coronal mass ejections (CMEs) during the 2010 August 1 events using STEREO/SECCHI COR and HI data. We obtain the direction of motion for both CMEs by applying several independent reconstruction methods and find that the CMEs head in similar directions. This provides evidence that a full interaction takes place between the two CMEs that can be observed in the HI1 field-of-view. The full de-projected kinematics of the faster CME from Sun to Earth is derived by combining remote observations with in situ measurements of the CME at 1 AU. The speed profile of the faster CME (CME2; ~1200 km/s) shows a strong deceleration over the distance range at which it reaches the slower, preceding CME (CME1; ~700 km/s). By applying a drag-based model we are able to reproduce the kinematical profile of CME2 suggesting that CME1 represents a magnetohydrodynamic obstacle for CME2 and that, after the interaction, the merged entity propagates as a single structure in an ambient flow of speed and density typical for quiet solar wind conditions. Observational facts show that magnetic forces may contribute to the enhanced deceleration of CME2. We speculate that the increase in magnetic tension and pressure, when CME2 bends and compresses the magnetic field lines of CME1, increases the efficiency of drag. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1202.0629v1-abstract-full').style.display = 'none'; document.getElementById('1202.0629v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 February, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">accepted for ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1201.0815">arXiv:1201.0815</a> <span> [<a href="https://arxiv.org/pdf/1201.0815">pdf</a>, <a href="https://arxiv.org/ps/1201.0815">ps</a>, <a href="https://arxiv.org/format/1201.0815">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Plasma Physics">physics.plasm-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/2041-8205/723/1/L53">10.1088/2041-8205/723/1/L53 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> First SDO AIA Observations of a Global Coronal EUV "Wave": Multiple Components and "Ripples" </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Liu%2C+W">Wei Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Schrijver%2C+C+J">Carolus J. Schrijver</a>, <a href="/search/astro-ph?searchtype=author&query=Title%2C+A+M">Alan M. Title</a>, <a href="/search/astro-ph?searchtype=author&query=Tarbell%2C+T+D">Theodore D. Tarbell</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1201.0815v1-abstract-short" style="display: inline;"> We present the first SDO AIA observations of a global coronal EUV disturbance (so-called "EIT wave") revealed in unprecedented detail. The disturbance observed on 2010 April 8 exhibits two components: one diffuse pulse superimposed on which are multiple sharp fronts that have slow and fast components. The disturbance originates in front of erupting coronal loops and some sharp fronts undergo accel… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1201.0815v1-abstract-full').style.display = 'inline'; document.getElementById('1201.0815v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1201.0815v1-abstract-full" style="display: none;"> We present the first SDO AIA observations of a global coronal EUV disturbance (so-called "EIT wave") revealed in unprecedented detail. The disturbance observed on 2010 April 8 exhibits two components: one diffuse pulse superimposed on which are multiple sharp fronts that have slow and fast components. The disturbance originates in front of erupting coronal loops and some sharp fronts undergo accelerations, both effects implying that the disturbance is driven by a CME. The diffuse pulse, propagating at a uniform velocity of 204-238 km/s with very little angular dependence within its extent in the south, maintains its coherence and stable profile for ~30 minutes. Its arrival at increasing distances coincides with the onsets of loop expansions and the slow sharp front. The fast sharp front overtakes the slow front, producing multiple "ripples" and steepening the local pulse, and both fronts propagate independently afterwards. This behavior resembles the nature of real waves. Unexpectedly, the amplitude and FWHM of the diffuse pulse decrease linearly with distance. A hybrid model, combining both wave and non-wave components, can explain many, but not all, of the observations. Discoveries of the two-component fronts and multiple ripples were made possible for the first time thanks to AIA's high cadences (10-20 s) and high signal-to-noise ratio. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1201.0815v1-abstract-full').style.display = 'none'; document.getElementById('1201.0815v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 January, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal Letters, 723: L53-L59, 2010 November 1 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1109.2925">arXiv:1109.2925</a> <span> [<a href="https://arxiv.org/pdf/1109.2925">pdf</a>, <a href="https://arxiv.org/format/1109.2925">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/0004-637X/744/1/72">10.1088/0004-637X/744/1/72 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Coronal Magnetic Field Measurement from EUV Images made by the Solar Dynamics Observatory </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gopalswamy%2C+N">Nat Gopalswamy</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a>, <a href="/search/astro-ph?searchtype=author&query=Akiyama%2C+S">Sachiko Akiyama</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%A4kel%C3%A4%2C+P">Pertti M盲kel盲</a>, <a href="/search/astro-ph?searchtype=author&query=Yashiro%2C+S">Seiji Yashiro</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1109.2925v1-abstract-short" style="display: inline;"> By measuring the geometrical properties of the coronal mass ejection (CME) flux rope and the leading shock observed on 2010 June 13 by the Solar Dynamics Observatory (SDO) mission's Atmospheric Imaging Assembly (AIA) we determine the Alfv茅n speed and the magnetic field strength in the inner corona at a heliocentric distance of ~ 1.4 Rs. The basic measurements are the shock standoff distance (delta… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1109.2925v1-abstract-full').style.display = 'inline'; document.getElementById('1109.2925v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1109.2925v1-abstract-full" style="display: none;"> By measuring the geometrical properties of the coronal mass ejection (CME) flux rope and the leading shock observed on 2010 June 13 by the Solar Dynamics Observatory (SDO) mission's Atmospheric Imaging Assembly (AIA) we determine the Alfv茅n speed and the magnetic field strength in the inner corona at a heliocentric distance of ~ 1.4 Rs. The basic measurements are the shock standoff distance (deltaR) ahead of the CME flux rope, the radius of curvature of the flux rope (Rc), and the shock speed. We first derive the Alfv茅nic Mach number (M) using the relationship, deltaR/Rc = 0.81[(gamma-1) M^2 + 2]/[(gamma+1)(M^2-1)], where gamma is the only parameter that needed to be assumed. For gamma =4/3, the Mach number declined from 3.7 to 1.5 indicating shock weakening within the field of view of the imager. The shock formation coincided with the appearance of a type II radio burst at a frequency of ~300 MHz (harmonic component), providing an independent confirmation of the shock. The shock compression ratio derived from the radio dynamic spectrum was found to be consistent with that derived from the theory of fast mode MHD shocks. From the measured shock speed and the derived Mach number, we found the Alfv茅n speed to increase from ~140 km/s to 460 km/s over the distance range 1.2 to 1.5 Rs. By deriving the upstream plasma density from the emission frequency of the associated type II radio burst, we determined the coronal magnetic field to be in the range 1.3 to 1.5 G. The derived magnetic field values are consistent with other estimates in a similar distance range. This work demonstrates that the EUV imagers, in the presence of radio dynamic spectra, can be used as coronal magnetometers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1109.2925v1-abstract-full').style.display = 'none'; document.getElementById('1109.2925v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 September, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2011. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">25 pages, 6 figures, 2 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1101.5232">arXiv:1101.5232</a> <span> [<a href="https://arxiv.org/pdf/1101.5232">pdf</a>, <a href="https://arxiv.org/ps/1101.5232">ps</a>, <a href="https://arxiv.org/format/1101.5232">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/2041-8205/727/2/L43">10.1088/2041-8205/727/2/L43 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Case Study of Four Homologous Large-Scale Coronal Waves Observed on 2010 April 28 and 29 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kienreich%2C+I+W">I. W. Kienreich</a>, <a href="/search/astro-ph?searchtype=author&query=Veronig%2C+A+M">A. M. Veronig</a>, <a href="/search/astro-ph?searchtype=author&query=Muhr%2C+N">N. Muhr</a>, <a href="/search/astro-ph?searchtype=author&query=Temmer%2C+M">M. Temmer</a>, <a href="/search/astro-ph?searchtype=author&query=Vrsnak%2C+B">B. Vrsnak</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">N. Nitta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1101.5232v1-abstract-short" style="display: inline;"> On 2010 April 28 and 29, the Solar TErrestrial Relations Observatory B/Extreme Ultraviolet Imager observed four homologous large-scale coronal waves, the so-called EIT-waves, within 8 hr. All waves emerged from the same source active region, were accompanied by weak flares and faint coronal mass ejections, and propagated into the same direction at constant velocities in the range of ~220-340 km s-… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1101.5232v1-abstract-full').style.display = 'inline'; document.getElementById('1101.5232v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1101.5232v1-abstract-full" style="display: none;"> On 2010 April 28 and 29, the Solar TErrestrial Relations Observatory B/Extreme Ultraviolet Imager observed four homologous large-scale coronal waves, the so-called EIT-waves, within 8 hr. All waves emerged from the same source active region, were accompanied by weak flares and faint coronal mass ejections, and propagated into the same direction at constant velocities in the range of ~220-340 km s-1. The last of these four coronal wave events was the strongest and fastest, with a velocity of 337 +/- 31 km s-1 and a peak perturbation amplitude of ~1.24, corresponding to a magnetosonic Mach number of Mms ~ 1.09. The magnetosonic Mach numbers and velocities of the four waves are distinctly correlated, suggestive of the nonlinear fast-mode magnetosonic wave nature of the events. We also found a correlation between the magnetic energy buildup times and the velocity and magnetosonic Mach number. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1101.5232v1-abstract-full').style.display = 'none'; document.getElementById('1101.5232v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 January, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2011. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal Letters, 727:L43 (6pp), 2011 February 1 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0805.4474">arXiv:0805.4474</a> <span> [<a href="https://arxiv.org/pdf/0805.4474">pdf</a>, <a href="https://arxiv.org/ps/0805.4474">ps</a>, <a href="https://arxiv.org/format/0805.4474">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/523842">10.1086/523842 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Characteristics of Anemone Active Regions Appearing in Coronal Holes Observed with {\it Yohkoh} Soft X-ray Telescope </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Asai%2C+A">Ayumi Asai</a>, <a href="/search/astro-ph?searchtype=author&query=Shibata%2C+K">Kazunari Shibata</a>, <a href="/search/astro-ph?searchtype=author&query=Hara%2C+H">Hirohisa Hara</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N+V">Nariaki V. Nitta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0805.4474v1-abstract-short" style="display: inline;"> Coronal structure of active regions appearing in coronal holes is studied by using the data obtained with the Soft X-Ray Telescope (SXT) aboard {\it Yohkoh} from 1991 November to 1993 March. The following characteristics are found; Many of active regions appearing in coronal holes show a structure that looks like a ``sea-anemone''. Such active regions are called {\it anemone ARs}. About one-fort… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0805.4474v1-abstract-full').style.display = 'inline'; document.getElementById('0805.4474v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0805.4474v1-abstract-full" style="display: none;"> Coronal structure of active regions appearing in coronal holes is studied by using the data obtained with the Soft X-Ray Telescope (SXT) aboard {\it Yohkoh} from 1991 November to 1993 March. The following characteristics are found; Many of active regions appearing in coronal holes show a structure that looks like a ``sea-anemone''. Such active regions are called {\it anemone ARs}. About one-forth of all active regions that were observed with SXT from their births showed the anemone structure. For almost all the anemone ARs, the order of magnetic polarities is consistent with the Hale-Nicholson's polarity law. These anemone ARs also showed more or less east-west asymmetry in X-ray intensity distribution, such that the following (eastern) part of the ARs is brighter than its preceding (western) part. This, as well as the anemone shape itself, is consistent with the magnetic polarity distribution around the anemone ARs. These observations also suggest that an active region appearing in coronal holes has simpler (less sheared) and more preceding-spot-dominant magnetic structure than those appearing in other regions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0805.4474v1-abstract-full').style.display = 'none'; document.getElementById('0805.4474v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 May, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 3 tables, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J.673:1188-1193,2008 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0004093">arXiv:astro-ph/0004093</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0004093">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0004093">ps</a>, <a href="https://arxiv.org/format/astro-ph/0004093">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/312695">10.1086/312695 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Effect of Hydrostatic Weighting on the Vertical Temperature Structure of the Solar Corona </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">Markus J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Nitta%2C+N">Nariaki Nitta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0004093v1-abstract-short" style="display: inline;"> We investigate the effect of hydrostatic scale heights $位(T)$ in coronal loops on the determination of the vertical temperature structure $T(h)$ of the solar corona. Every method that determines an average temperature at a particular line-of-sight from optically thin emission (e.g. in EUV or soft X-ray wavelengths) of a mutli-temperature plasma, is subject to the emission measure-weighted contri… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0004093v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0004093v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0004093v1-abstract-full" style="display: none;"> We investigate the effect of hydrostatic scale heights $位(T)$ in coronal loops on the determination of the vertical temperature structure $T(h)$ of the solar corona. Every method that determines an average temperature at a particular line-of-sight from optically thin emission (e.g. in EUV or soft X-ray wavelengths) of a mutli-temperature plasma, is subject to the emission measure-weighted contributions $dEM(T)/dT$ from different temperatures. Because most of the coronal structures (along open or closed field lines) are close to hydrostatic equilibrium, the hydrostatic temperature scale height introduces a height-dependent weighting function that causes a systematic bias in the determination of the temperature structure $T(h)$ as function of altitude $h$. The net effect is that the averaged temperature seems to increase with altitude, $dT(h)/dh > 0$, even if every coronal loop (of a multi-temperature ensemble) is isothermal in itself. We simulate this effect with differential emission measure distributions observed by {\sl SERTS} for an instrument with a broadband temperature filter such as {\sl Yohkoh/SXT} and find that the apparent temperature increase due to hydrostatic weighting is of order $螖T \approx T_0 \times h/r_{\sun}$. We suggest that this effect largely explains the systematic temperature increase in the upper corona reported in recent studies (e.g. by Sturrock et al., Wheatland et al., or Priest et al.), rather than being an intrinsic signature of a coronal heating mechanism. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0004093v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0004093v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 April, 2000; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2000. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 3 figures. ApJ Letters, accepted 2000 April 6, in press</span> </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/about">About</a></li> <li><a href="https://info.arxiv.org/help">Help</a></li> </ul> </div> <div class="column"> <ul class="nav-spaced"> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>contact arXiv</title><desc>Click here to contact arXiv</desc><path d="M502.3 190.8c3.9-3.1 9.7-.2 9.7 4.7V400c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V195.6c0-5 5.7-7.8 9.7-4.7 22.4 17.4 52.1 39.5 154.1 113.6 21.1 15.4 56.7 47.8 92.2 47.6 35.7.3 72-32.8 92.3-47.6 102-74.1 131.6-96.3 154-113.7zM256 320c23.2.4 56.6-29.2 73.4-41.4 132.7-96.3 142.8-104.7 173.4-128.7 5.8-4.5 9.2-11.5 9.2-18.9v-19c0-26.5-21.5-48-48-48H48C21.5 64 0 85.5 0 112v19c0 7.4 3.4 14.3 9.2 18.9 30.6 23.9 40.7 32.4 173.4 128.7 16.8 12.2 50.2 41.8 73.4 41.4z"/></svg> <a href="https://info.arxiv.org/help/contact.html"> Contact</a> </li> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>subscribe to arXiv mailings</title><desc>Click here to subscribe</desc><path d="M476 3.2L12.5 270.6c-18.1 10.4-15.8 35.6 2.2 43.2L121 358.4l287.3-253.2c5.5-4.9 13.3 2.6 8.6 8.3L176 407v80.5c0 23.6 28.5 32.9 42.5 15.8L282 426l124.6 52.2c14.2 6 30.4-2.9 33-18.2l72-432C515 7.8 493.3-6.8 476 3.2z"/></svg> <a href="https://info.arxiv.org/help/subscribe"> Subscribe</a> </li> </ul> </div> </div> </div>   <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/help/license/index.html">Copyright</a></li> <li><a href="https://info.arxiv.org/help/policies/privacy_policy.html">Privacy Policy</a></li> </ul> </div> <div class="column sorry-app-links"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/help/web_accessibility.html">Web Accessibility Assistance</a></li> <li> <p class="help"> <a class="a11y-main-link" href="https://status.arxiv.org" target="_blank">arXiv Operational Status <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 512" class="icon filter-dark_grey" role="presentation"><path d="M224.3 273l-136 136c-9.4 9.4-24.6 9.4-33.9 0l-22.6-22.6c-9.4-9.4-9.4-24.6 0-33.9l96.4-96.4-96.4-96.4c-9.4-9.4-9.4-24.6 0-33.9L54.3 103c9.4-9.4 24.6-9.4 33.9 0l136 136c9.5 9.4 9.5 24.6.1 34z"/></svg></a><br> Get status notifications via <a class="is-link" href="https://subscribe.sorryapp.com/24846f03/email/new" target="_blank"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><path d="M502.3 190.8c3.9-3.1 9.7-.2 9.7 4.7V400c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V195.6c0-5 5.7-7.8 9.7-4.7 22.4 17.4 52.1 39.5 154.1 113.6 21.1 15.4 56.7 47.8 92.2 47.6 35.7.3 72-32.8 92.3-47.6 102-74.1 131.6-96.3 154-113.7zM256 320c23.2.4 56.6-29.2 73.4-41.4 132.7-96.3 142.8-104.7 173.4-128.7 5.8-4.5 9.2-11.5 9.2-18.9v-19c0-26.5-21.5-48-48-48H48C21.5 64 0 85.5 0 112v19c0 7.4 3.4 14.3 9.2 18.9 30.6 23.9 40.7 32.4 173.4 128.7 16.8 12.2 50.2 41.8 73.4 41.4z"/></svg>email</a> or <a class="is-link" href="https://subscribe.sorryapp.com/24846f03/slack/new" target="_blank"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512" class="icon filter-black" role="presentation"><path d="M94.12 315.1c0 25.9-21.16 47.06-47.06 47.06S0 341 0 315.1c0-25.9 21.16-47.06 47.06-47.06h47.06v47.06zm23.72 0c0-25.9 21.16-47.06 47.06-47.06s47.06 21.16 47.06 47.06v117.84c0 25.9-21.16 47.06-47.06 47.06s-47.06-21.16-47.06-47.06V315.1zm47.06-188.98c-25.9 0-47.06-21.16-47.06-47.06S139 32 164.9 32s47.06 21.16 47.06 47.06v47.06H164.9zm0 23.72c25.9 0 47.06 21.16 47.06 47.06s-21.16 47.06-47.06 47.06H47.06C21.16 243.96 0 222.8 0 196.9s21.16-47.06 47.06-47.06H164.9zm188.98 47.06c0-25.9 21.16-47.06 47.06-47.06 25.9 0 47.06 21.16 47.06 47.06s-21.16 47.06-47.06 47.06h-47.06V196.9zm-23.72 0c0 25.9-21.16 47.06-47.06 47.06-25.9 0-47.06-21.16-47.06-47.06V79.06c0-25.9 21.16-47.06 47.06-47.06 25.9 0 47.06 21.16 47.06 47.06V196.9zM283.1 385.88c25.9 0 47.06 21.16 47.06 47.06 0 25.9-21.16 47.06-47.06 47.06-25.9 0-47.06-21.16-47.06-47.06v-47.06h47.06zm0-23.72c-25.9 0-47.06-21.16-47.06-47.06 0-25.9 21.16-47.06 47.06-47.06h117.84c25.9 0 47.06 21.16 47.06 47.06 0 25.9-21.16 47.06-47.06 47.06H283.1z"/></svg>slack</a> </p> </li> </ul> </div> </div> </div>  </div> </footer> <script src="https://static.arxiv.org/static/base/1.0.0a5/js/member_acknowledgement.js"></script> </body> </html>

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