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</div> <div class="control"> <button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Aschwanden%2C+M+J&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Aschwanden%2C+M+J&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Aschwanden%2C+M+J&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <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/2211.08323">arXiv:2211.08323</a> <span> [<a href="https://arxiv.org/pdf/2211.08323">pdf</a>, <a href="https://arxiv.org/ps/2211.08323">ps</a>, <a href="https://arxiv.org/format/2211.08323">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"> The Universality of Power Law Slopes in the Solar Photosphere and Transition Region Observed with HMI and IRIS </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=Nhalil%2C+N+V">Nived Vilangot Nhalil</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="2211.08323v3-abstract-short" style="display: inline;"> We compare the size distributions of self-organized criticality (SOC) systems in the solar photosphere and the transition region, using magnetogram data from Helioseismic and Magnetic Imager (HMI) and Interface Region Imaging Spectrograph (IRIS)} data. For each dataset we fit a combination of a Gaussian and a power law size distribution function, which yields information on four different physical… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.08323v3-abstract-full').style.display = 'inline'; document.getElementById('2211.08323v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.08323v3-abstract-full" style="display: none;"> We compare the size distributions of self-organized criticality (SOC) systems in the solar photosphere and the transition region, using magnetogram data from Helioseismic and Magnetic Imager (HMI) and Interface Region Imaging Spectrograph (IRIS)} data. For each dataset we fit a combination of a Gaussian and a power law size distribution function, which yields information on four different physical processes: (i) Gaussian random noise in IRIS data; (ii) spicular events in the plages of the transition region (described by power law size distribution in IRIS data); (iii) salt-and-pepper small-scale magnetic structures (described by the random noise in HMI magnetograms); and (iv) magnetic reconnection processes in flares and nanoflares (described by power law size distributions in HMI data). We find a high correlation (CCC=0.90) between IRIS and HMI data. Datasets with magnetic flux balance are generally found to match the SOC-predicted power law slope a_F=1.80 (for mean fluxes F), but exceptions occur due to arbitrary choices of the HMI field-of-view. The matching cases confirm the universality of SOC-inferred flux size distributions, and agree with the results of Parnell et al.~(2009), a_F=1.85 +/- 0.14. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.08323v3-abstract-full').style.display = 'none'; document.getElementById('2211.08323v3-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, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 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">text 17 pages, 3 Tables, 8 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/2207.12894">arXiv:2207.12894</a> <span> [<a href="https://arxiv.org/pdf/2207.12894">pdf</a>, <a href="https://arxiv.org/format/2207.12894">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"> Interface Region Imaging Spectrograph (IRIS) Observations of the Fractal Dimension in the Solar Atmosphere </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=Nhalil%2C+N+V">Nived Vilangot Nhalil</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="2207.12894v1-abstract-short" style="display: inline;"> While previous work explored the fractality and self-organized criticality (SOC) of flares and nanoflares in wavelengths emitted in the solar corona (such as in hard X-rays, soft X-rays, and EUV wavelenghts), we focus here on impulsive phenomena in the photosphere and transition region, as observed with the {\sl Interface Region Imaging Spectrograph (IRIS)} in the temperature range of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.12894v1-abstract-full').style.display = 'inline'; document.getElementById('2207.12894v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2207.12894v1-abstract-full" style="display: none;"> While previous work explored the fractality and self-organized criticality (SOC) of flares and nanoflares in wavelengths emitted in the solar corona (such as in hard X-rays, soft X-rays, and EUV wavelenghts), we focus here on impulsive phenomena in the photosphere and transition region, as observed with the {\sl Interface Region Imaging Spectrograph (IRIS)} in the temperature range of $T_e \approx 10^4-10^6$ K. We find the following fractal dimensions (in increasing order): $D_A=1.21 \pm 0.07$ for photospheric granulation, $D_A=1.29 \pm 0.15$ for plages in the transition region, $D_A=1.54 \pm 0.16$ for sunspots in the transition region, $D_A=1.59 \pm 0.08$ for magnetograms in active regions, $D_A=1.56 \pm 0.08$ for EUV nanoflares, $D_A=1.76 \pm 0.14$ for large solar flares, and up to $D_A=1.89 \pm 0.05$ for the largest X-class flares. We interpret low values of the fractal dimension ($1.0 \lapprox D_A \lapprox 1.5$) in terms of sparse curvi-linear flow patterns, while high values of the fractal dimension ($1.5 \lapprox D_A \lapprox 2.0$) indicate near space-filling transport processes, such as chromospheric evaporation. Phenomena in the solar transition region appear to be consistent with SOC models, based on their size distributions of fractal areas $A$ and (radiative) energies $E$, which show power law slopes of $伪_A^{obs}=2.51 \pm 0.21$ (with $伪_A^{theo}=2.33$ predicted), and $伪_E^{obs}=2.03 \pm 0.18$ (with $伪_E^{theo}=1.80$ predicted). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.12894v1-abstract-full').style.display = 'none'; document.getElementById('2207.12894v1-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, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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 text, 3 Tables, 5 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/2203.12484">arXiv:2203.12484</a> <span> [<a href="https://arxiv.org/pdf/2203.12484">pdf</a>, <a href="https://arxiv.org/ps/2203.12484">ps</a>, <a href="https://arxiv.org/format/2203.12484">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="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chaotic Dynamics">nlin.CD</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/ac7b8d">10.3847/2041-8213/ac7b8d <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Reconciling Power Law Slopes in Solar Flare and Nanoflare Size Distributions </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> </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="2203.12484v2-abstract-short" style="display: inline;"> We unify the power laws of size distributions of solar flare and nanoflare energies. We present three models that predict the power law slopes $伪_E$ of flare energies defined in terms of the 2-D and 3-D fractal dimensions ($D_A, D_V$): (i) The spatio-temporal standard SOC model, defined by the power law slope $伪_{E1}=1+2/(D_V+2)=(13/9)\approx 1.44$; (ii) the 2-D thermal energy model,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.12484v2-abstract-full').style.display = 'inline'; document.getElementById('2203.12484v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.12484v2-abstract-full" style="display: none;"> We unify the power laws of size distributions of solar flare and nanoflare energies. We present three models that predict the power law slopes $伪_E$ of flare energies defined in terms of the 2-D and 3-D fractal dimensions ($D_A, D_V$): (i) The spatio-temporal standard SOC model, defined by the power law slope $伪_{E1}=1+2/(D_V+2)=(13/9)\approx 1.44$; (ii) the 2-D thermal energy model, $伪_{E2}=1+2/D_A=(7/3)\approx 2.33$, and (iii) the 3-D thermal energy model, $伪_{E3}=1+2/D_V=(9/5)\approx 1.80$. The theoretical predictions of energies are consistent with the observational values of these three groups, i.e., $伪_{E1}=1.47 \pm 0.07$; $伪_{E2}=2.38 \pm 0.09$, and $伪_{E3}=1.80 \pm 0.18$. These results corroborate that the energy of nanoflares does not diverge at small energies, since $(伪_{E1}<2$) and $(伪_{E3}<2)$, except for the unphyiscal 2-D model $(伪_{E2}>2)$. This conclusion adds an additional argument against the scenario of coronal heating by nanoflares. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.12484v2-abstract-full').style.display = 'none'; document.getElementById('2203.12484v2-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> 2 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">12 pages, 3 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/2112.07759">arXiv:2112.07759</a> <span> [<a href="https://arxiv.org/pdf/2112.07759">pdf</a>, <a href="https://arxiv.org/ps/2112.07759">ps</a>, <a href="https://arxiv.org/format/2112.07759">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"> Global energetics of solar flares. XIII. The Neupert effect and acceleration of coronal mass ejections </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> </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="2112.07759v1-abstract-short" style="display: inline;"> Our major aim is a height-time model $r(t)$ of the propagation of {\sl Coronal Mass Ejections (CMEs)}, where the lower corona is self-consistently connected to the heliospheric path. We accomplish this task by using the Neupert effect to derive the peak time, duration, and rate of the CME acceleration phase, as obtained from the time derivative of the {\sl soft X-ray (SXR)} light curve. This novel… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.07759v1-abstract-full').style.display = 'inline'; document.getElementById('2112.07759v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.07759v1-abstract-full" style="display: none;"> Our major aim is a height-time model $r(t)$ of the propagation of {\sl Coronal Mass Ejections (CMEs)}, where the lower corona is self-consistently connected to the heliospheric path. We accomplish this task by using the Neupert effect to derive the peak time, duration, and rate of the CME acceleration phase, as obtained from the time derivative of the {\sl soft X-ray (SXR)} light curve. This novel approach offers the advantage to obtain the kinematics of the CME height-time profile $r(t)$, the CME velocity profile $v(t)=dr(t)/dt$, and the CME acceleration profile $a(t)=dv(t)/dt$ from {\sl Geostationary Orbiting Earth Satellite (GOES)} and white-light data, without the need of {\sl hard X-ray (HXR)} data. We apply this technique to a data set of 576 (GOES X and M-class) flare events observed with GOES and the {\sl Large Angle Solar Coronagraph (LASCO)}. Our analysis yields acceleration rates in the range of $a_A = 0.1-13$ km s$^{-2}$, acceleration durations of $蟿_A = 1.2-45$ min, and acceleration distances in the range of $d_A = 3-1063$ Mm, with a median of $d_A=39$ Mm, which corresponds to the hydrostatic scale height of a corona with a temperature of $T_e \approx 0.8$ MK. The results are consistent with standard flare/CME models that predict magnetic reconnection and synchronized (primary) acceleration of CMEs in the low corona (at a height of ~0.1 R_sun), while secondary (weaker) acceleration may occur further out at heliospheric distances. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.07759v1-abstract-full').style.display = 'none'; document.getElementById('2112.07759v1-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 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">11 pages text + 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/2107.13621">arXiv:2107.13621</a> <span> [<a href="https://arxiv.org/pdf/2107.13621">pdf</a>, <a href="https://arxiv.org/ps/2107.13621">ps</a>, <a href="https://arxiv.org/format/2107.13621">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/ac2a29">10.3847/1538-4357/ac2a29 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Solar Memory From Hours to Decades </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=Johnson%2C+J+R">Jay R. Johnson</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="2107.13621v1-abstract-short" style="display: inline;"> Waiting time distributions allow us to distinguish at least three different types of dynamical systems, such as (i) linear random processes (with no memory); (ii) nonlinear, avalanche-type, nonstationary Poisson processes (with memory during the exponential growth of the avalanche rise time); and (iii) chaotic systems in the state of a nonlinear limit cycle (with memory during the oscillatory phas… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.13621v1-abstract-full').style.display = 'inline'; document.getElementById('2107.13621v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.13621v1-abstract-full" style="display: none;"> Waiting time distributions allow us to distinguish at least three different types of dynamical systems, such as (i) linear random processes (with no memory); (ii) nonlinear, avalanche-type, nonstationary Poisson processes (with memory during the exponential growth of the avalanche rise time); and (iii) chaotic systems in the state of a nonlinear limit cycle (with memory during the oscillatory phase). We describe the temporal evolution of the flare rate $位(t) \propto t^p$ with a polynomial function, which allows us to distinguish linear ($p \approx 1$) from nonlinear ($p \gapprox 2$) events. The power law slopes $伪$ of observed waiting times (with full solar cycle coverage) cover a range of $伪=2.1-2.4$, which agrees well with our prediction of $伪= 2.0+1/p = 2.3-2.5$. The memory time can also be defined with the time evolution of the logistic equation, for which we find a relationship between the nonlinear growth time $蟿_G = 蟿_{rise}/(4p)$ and the nonlinearity index $p$. We find a nonlinear evolution for most events, in particular for the clustering of solar flares ($p=2.2\pm0.1$), partially occulted flare events ($p=1.8\pm0.2$), and the solar dynamo ($p=2.8\pm0.5$). The Sun exhibits memory on time scales of $\lapprox$2 hours to 3 days (for solar flare clustering), 6 to 23 days (for partially occulted flare events), and 1.5 month to 1 year (for the rise time of the solar dynamo). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.13621v1-abstract-full').style.display = 'none'; document.getElementById('2107.13621v1-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 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">11 pages, 1 Table, 5 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/2107.13065">arXiv:2107.13065</a> <span> [<a href="https://arxiv.org/pdf/2107.13065">pdf</a>, <a href="https://arxiv.org/ps/2107.13065">ps</a>, <a href="https://arxiv.org/format/2107.13065">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/ac19a9">10.3847/1538-4357/ac19a9 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Poissonian Origin of Power Laws in Solar Flare Waiting Time Distributions </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=Johnson%2C+J+R">Jay R. Johnson</a>, <a href="/search/astro-ph?searchtype=author&query=Nurhan%2C+Y+I">Yosia I. Nurhan</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="2107.13065v1-abstract-short" style="display: inline;"> In this study we aim for a deeper understanding of the power law slope, $伪$, of waiting time distributions. Statistically independent events with linear behavior can be characterized by binomial, Gaussian, exponential, or Poissonian size distribution functions. In contrast, physical processes with nonlinear behavior exhibit spatio-temporal coherence (or memory) and "fat tails" in their size distri… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.13065v1-abstract-full').style.display = 'inline'; document.getElementById('2107.13065v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.13065v1-abstract-full" style="display: none;"> In this study we aim for a deeper understanding of the power law slope, $伪$, of waiting time distributions. Statistically independent events with linear behavior can be characterized by binomial, Gaussian, exponential, or Poissonian size distribution functions. In contrast, physical processes with nonlinear behavior exhibit spatio-temporal coherence (or memory) and "fat tails" in their size distributions that fit power law-like functions, as a consequence of the time variability of the mean event rate, as demonstrated by means of Bayesian block decomposition in the work of Wheatland et al.~(1998). In this study we conduct numerical simulations of waiting time distributions $N(蟿)$ in a large parameter space for various (polynomial, sinusoidal, Gaussian) event rate functions $位(t)$, parameterized with an exponent $p$ that expresses the degree of the polynomial function $位(t) \propto t^p$. We derive an analytical exact solution of the waiting time distribution function in terms of the incomplete gamma function, which is similar to a Pareto type-II function and has a power law slope of $伪= 2 + 1/p$, in the asymptotic limit of large waiting times. Numerically simulated random distributions reproduce this theoretical prediction accurately. Numerical simulations in the nonlinear regime ($p \ge 2$) predict power law slopes in the range of $2.0 \le 伪\le 2.5$. The self-organized criticality model yields a prediction of $伪=2$. Observations of solar flares and coronal mass ejections (over at least a half solar cycle) are found in the range of $伪_{obs} \approx 2.1-2.4$. Deviations from strict power law functions are expected due to the variability of the flare event rate $位(t)$, and deviations from theoretically predicted slope values $伪$ occur due to the Poissonian weighting bias of power law fits. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.13065v1-abstract-full').style.display = 'none'; document.getElementById('2107.13065v1-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 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">14 pages, 7 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/2106.06490">arXiv:2106.06490</a> <span> [<a href="https://arxiv.org/pdf/2106.06490">pdf</a>, <a href="https://arxiv.org/ps/2106.06490">ps</a>, <a href="https://arxiv.org/format/2106.06490">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/abdec7">10.3847/1538-4357/abdec7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Self-Organized Criticality in Stellar Flares </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=Guedel%2C+M">Manuel Guedel</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="2106.06490v1-abstract-short" style="display: inline;"> Power law size distributions are the hallmarks of nonlinear energy dissipation processes governed by self-organized criticality. Here we analyze 75 data sets of stellar flare size distributions, mostly obtained from the {\sl Extreme Ultra-Violet Explorer (EUVE)} and the {\sl Kepler} mission. We aim to answer the following questions for size distributions of stellar flares: (i) What are the values… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.06490v1-abstract-full').style.display = 'inline'; document.getElementById('2106.06490v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.06490v1-abstract-full" style="display: none;"> Power law size distributions are the hallmarks of nonlinear energy dissipation processes governed by self-organized criticality. Here we analyze 75 data sets of stellar flare size distributions, mostly obtained from the {\sl Extreme Ultra-Violet Explorer (EUVE)} and the {\sl Kepler} mission. We aim to answer the following questions for size distributions of stellar flares: (i) What are the values and uncertainties of power law slopes? (ii) Do power law slopes vary with time ? (iii) Do power law slopes depend on the stellar spectral type? (iv) Are they compatible with solar flares? (v) Are they consistent with self-organized criticality (SOC) models? We find that the observed size distributions of stellar flare fluences (or energies) exhibit power law slopes of $伪_E=2.09\pm0.24$ for optical data sets observed with Kepler. The observed power law slopes do not show much time variability and do not depend on the stellar spectral type (M, K, G, F, A, Giants). In solar flares we find that background subtraction lowers the uncorrected value of $伪_E=2.20\pm0.22$ to $伪_E=1.57\pm0.19$. Furthermore, most of the stellar flares are temporally not resolved in low-cadence (30 min) Kepler data, which causes an additional bias. Taking these two biases into account, the stellar flare data sets are consistent with the theoretical prediction $N(x) \propto x^{-伪_x}$ of self-organized criticality models, i.e., $伪_E=1.5$. Thus, accurate power law fits require automated detection of the inertial range and background subtraction, which can be modeled with the generalized Pareto distribution, finite-system size effects, and extreme event outliers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.06490v1-abstract-full').style.display = 'none'; document.getElementById('2106.06490v1-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 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">16 pages, 7 Figures, 3 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/2102.02305">arXiv:2102.02305</a> <span> [<a href="https://arxiv.org/pdf/2102.02305">pdf</a>, <a href="https://arxiv.org/ps/2102.02305">ps</a>, <a href="https://arxiv.org/format/2102.02305">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/abef69">10.3847/1538-4357/abef69 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Correlation of the sunspot number and the waiting time distribution of solar flares, coronal mass ejections, and solar wind switchback events observed with the Parker Solar Probe </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=de+Wit%2C+T+D">Thierry Dudok de Wit</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="2102.02305v1-abstract-short" style="display: inline;"> Waiting time distributions of solar flares and {\sl coronal mass ejections (CMEs)} exhibit power law-like distribution functions with slopes in the range of $伪_蟿 \approx 1.4-3.2$, as observed in annual data sets during 4 solar cycles (1974-2012). We find a close correlation between the waiting time power law slope $伪_蟿$ and the {\sl sunspot number (SN)}, i.e., $伪_蟿$ = 1.38 + 0.01 $\times$ SN. The… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.02305v1-abstract-full').style.display = 'inline'; document.getElementById('2102.02305v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2102.02305v1-abstract-full" style="display: none;"> Waiting time distributions of solar flares and {\sl coronal mass ejections (CMEs)} exhibit power law-like distribution functions with slopes in the range of $伪_蟿 \approx 1.4-3.2$, as observed in annual data sets during 4 solar cycles (1974-2012). We find a close correlation between the waiting time power law slope $伪_蟿$ and the {\sl sunspot number (SN)}, i.e., $伪_蟿$ = 1.38 + 0.01 $\times$ SN. The waiting time distribution can be fitted with a Pareto-type function of the form $N(蟿) = N_0$ $(蟿_0 + 蟿)^{-伪_蟿}$, where the offset $蟿_0$ depends on the instrumental sensitivity, the detection threshold of events, and pulse pile-up effects. The time-dependent power law slope $伪_蟿(t)$ of waiting time distributions depends only on the global solar magnetic flux (quantified by the sunspot number) or flaring rate, independent of other physical parameters of {\sl self-organized criticality (SOC)} or {\sl magneto-hydrodynamic (MHD)} turbulence models. Power law slopes of $伪_蟿\approx 1.2-1.6$ were also found in solar wind switchback events, as observed with the {\sl Parker Solar Probe (PSP)}. We conclude that the annual variability of switchback events in the heliospheric solar wind is modulated by flare and CME rates originating in the photosphere and lower corona. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.02305v1-abstract-full').style.display = 'none'; document.getElementById('2102.02305v1-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, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">12 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> (2021), ApJ 912:94 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.03124">arXiv:2101.03124</a> <span> [<a href="https://arxiv.org/pdf/2101.03124">pdf</a>, <a href="https://arxiv.org/ps/2101.03124">ps</a>, <a href="https://arxiv.org/format/2101.03124">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/abda48">10.3847/1538-4357/abda48 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Finite System-Size Effects in Self-Organized Criticality Systems </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> </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="2101.03124v1-abstract-short" style="display: inline;"> We explore upper limits for the largest avalanches or catastrophes in nonlinear energy dissipation systems governed by self-organized criticality (SOC). We generalize the idealized "straight" power low size distribution and Pareto distribution functions in order to accomodate for incomplete sampling, limited instrumental sensitivity, finite system-size effects, "Black-Swan" and "Dragon-King" extre… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.03124v1-abstract-full').style.display = 'inline'; document.getElementById('2101.03124v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.03124v1-abstract-full" style="display: none;"> We explore upper limits for the largest avalanches or catastrophes in nonlinear energy dissipation systems governed by self-organized criticality (SOC). We generalize the idealized "straight" power low size distribution and Pareto distribution functions in order to accomodate for incomplete sampling, limited instrumental sensitivity, finite system-size effects, "Black-Swan" and "Dragon-King" extreme events. Our findings are: (i) Solar flares show no finite system-size limits up to L < 200 Mm, but solar flare durations reveal an upper flare duration limit of < 6 hrs; (ii) Stellar flares observed with KEPLER exhibit inertial ranges of $E \approx 10^{34}-10^{37}$ erg, finite system-size ranges at $E \approx 10^{37}-10^{38}$ erg, and extreme events at $E =(1-5) \times 10^{38}$ erg; (iii) The maximum flare energy of different spectral-type stars (M, K, G, F, A, Giants) reveal a positive correlation with the stellar radius, which indicates a finite system-size limit imposed by the stellar surface area. Fitting our finite system-size models to terrestrial data sets (Earth quakes, wildfires, city sizes, blackouts, terrorism, words, surnames, web-links) yields evidence (in half of the cases) for finite system-size limits and extreme events, which can be modeled with dual power law size distributions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.03124v1-abstract-full').style.display = 'none'; document.getElementById('2101.03124v1-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 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">21 pages, 10 Figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> (2021), ApJ 909:69 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.04419">arXiv:2007.04419</a> <span> [<a href="https://arxiv.org/pdf/2007.04419">pdf</a>, <a href="https://arxiv.org/ps/2007.04419">ps</a>, <a href="https://arxiv.org/format/2007.04419">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/abb946">10.3847/1538-4357/abb946 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares. XII. Energy Scaling Laws </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> </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="2007.04419v2-abstract-short" style="display: inline;"> In this study we test 30 variants of 5 physical scaling laws that describe different aspects of solar flares. We express scaling laws in terms of the magnetic potential field energy $E_p$, the mean potential field strength $B_p$, the free energy $E_{free}$, the dissipated magnetic flare energy $E_{diss}$, the mean loop length scale $L$, the mean helically twisted flux tube radius $R$, the sunspot… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.04419v2-abstract-full').style.display = 'inline'; document.getElementById('2007.04419v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.04419v2-abstract-full" style="display: none;"> In this study we test 30 variants of 5 physical scaling laws that describe different aspects of solar flares. We express scaling laws in terms of the magnetic potential field energy $E_p$, the mean potential field strength $B_p$, the free energy $E_{free}$, the dissipated magnetic flare energy $E_{diss}$, the mean loop length scale $L$, the mean helically twisted flux tube radius $R$, the sunspot radius $r$, the emission measure-weighted flare temperature $T_w$, the electron density $n_e$, and the total emission measure $EM$, measured from a data set of $\lapprox 400$ GOES M- and X-class flare events. The 5 categories of physical scaling laws include (i) a scaling law of the potential-field energy, (ii) a scaling law for helical twisting, (iii) a scaling law for Petschek-type magnetic reconnection, (iv) the Rosner-Tucker-Vaiana scaling law, and (v) the Shibata-Yokoyama scaling law. We test the self-consistency of these theoretical scaling laws with observed parameters by requiring two conditions: a cross-corrleation coefficient of CCC$>$0.5 between the observed and theoretically predicted scaling laws, and a linear regression fit with a slope of $伪\approx 1$. With these two criteria we find that 10 out of the 30 tested scaling law variants are consistent with the observed data, which strongly corroborates the existence and validity of the tested flare scaling laws. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.04419v2-abstract-full').style.display = 'none'; document.getElementById('2007.04419v2-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, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 8 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">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/2007.04413">arXiv:2007.04413</a> <span> [<a href="https://arxiv.org/pdf/2007.04413">pdf</a>, <a href="https://arxiv.org/ps/2007.04413">ps</a>, <a href="https://arxiv.org/format/2007.04413">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/ab9630">10.3847/1538-4357/ab9630 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares. XI. Flare Magnitude Predictions of the GOES-Class </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> </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="2007.04413v1-abstract-short" style="display: inline;"> In this study we determine scaling relationships of observed solar flares that can be used to predict upper limits of the GOES-class magnitude of solar flares. The flare prediction scheme is based on the scaling of the slowly-varying potential energy $E_p(t)$, which is extrapolated in time over an interval of $螖t \le$ 24 hrs. The observed scaling of the dissipated energy $E_{diss}$ scales with the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.04413v1-abstract-full').style.display = 'inline'; document.getElementById('2007.04413v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.04413v1-abstract-full" style="display: none;"> In this study we determine scaling relationships of observed solar flares that can be used to predict upper limits of the GOES-class magnitude of solar flares. The flare prediction scheme is based on the scaling of the slowly-varying potential energy $E_p(t)$, which is extrapolated in time over an interval of $螖t \le$ 24 hrs. The observed scaling of the dissipated energy $E_{diss}$ scales with the potential field energy as $E_{diss} \propto E_p^{1.32}$. In addition, the observed scaling relationship of the flare volume, $V \propto E_{diss}^{1.17}$, the multi-thermal energy, $E_{th} \propto V^{0.76}$, the flare emission measure $EM \propto E_{th}^{0.79}$, the EM-weighted temperature $T_{w}$, and the GOES flux, $F_8(t) \propto E_p(t)^{0.92}$, allows us then to predict an upper limit of the GOES-class flare magnitude in the extrapolated time window. We find a good correlation (CCC$\approx 0.7$) between the observed and predicted GOES-class flare magnitudes (in 172 X and M-class events). This is the first algorithm that employs observed scaling laws of physical flare parameters to predict GOES flux upper limits, an important capability that complements previous flare prediction methods based on machine-learning algorithms used in space weather forecasting. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.04413v1-abstract-full').style.display = 'none'; document.getElementById('2007.04413v1-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 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">4 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 Vol. 897:16, (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.04404">arXiv:2007.04404</a> <span> [<a href="https://arxiv.org/pdf/2007.04404">pdf</a>, <a href="https://arxiv.org/format/2007.04404">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/ab8aec">10.3847/1538-4357/ab8aec <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares: X. Petschek Reconnection Rate and Alfven Mach Number of Magnetic Reconnection Outflows </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> </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="2007.04404v1-abstract-short" style="display: inline;"> We investigate physical scaling laws for magnetic energy dissipation in solar flares, in the framework of the Sweet-Parker model and the Petschek model. We find that the total dissipated magnetic energy $E_{diss}$ in a flare depends on the mean magnetic field component $B_f$ associated with the free energy $E_f$, the length scale $L$ of the magnetic area, the hydrostatic density scale height $位$ o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.04404v1-abstract-full').style.display = 'inline'; document.getElementById('2007.04404v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.04404v1-abstract-full" style="display: none;"> We investigate physical scaling laws for magnetic energy dissipation in solar flares, in the framework of the Sweet-Parker model and the Petschek model. We find that the total dissipated magnetic energy $E_{diss}$ in a flare depends on the mean magnetic field component $B_f$ associated with the free energy $E_f$, the length scale $L$ of the magnetic area, the hydrostatic density scale height $位$ of the solar corona, the Alfv茅n Mach number $M_A=v_1/v_A$ (the ratio of the inflow speed $v_1$ to the Alfv茅nic outflow speed $v_A$), and the flare duration $蟿_f$, i.e., $E_{diss} = (1/4蟺) B_f^2\ L\ 位 v_A\ M_A\ 蟿_f$, where the Alfv茅n speed depends on the nonpotential field strength $B_{np}$ and the mean electron density $n_e$ in the reconnection outflow. Using MDI/SDO and AIA/SDO observations and 3-D magnetic field solutions obtained with the vertical-current approximation nonlinear force-free field code (VCA-NLFFF) we measure all physical parameters necessary to test scaling laws, which represents a new method to measure Alfv茅n Mach numbers $M_A$, the reconnection rate, and the total free energy dissipated in solar flares. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.04404v1-abstract-full').style.display = 'none'; document.getElementById('2007.04404v1-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 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">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 Vol. 895:134, (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2001.10103">arXiv:2001.10103</a> <span> [<a href="https://arxiv.org/pdf/2001.10103">pdf</a>, <a href="https://arxiv.org/ps/2001.10103">ps</a>, <a href="https://arxiv.org/format/2001.10103">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/ab7120">10.3847/1538-4357/ab7120 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Torsional Alfv茅nic Oscillations Discovered in the Magnetic Free Energy During Solar Flares </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=Wang%2C+T">Tongjiang 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="2001.10103v1-abstract-short" style="display: inline;"> We report the discovery of torsional Alfv茅nic oscillations in solar flares, which modulate the time evolution of the magnetic free energy $E_f(t)$, while the magnetic potential energy $E_p(t)$ is uncorrelated, and the nonpotential energy varies as $E_{np}(t) = E_p + E_f(t)$. The mean observed time period of the torsional oscillations is $P_{obs}=15.1 \pm 3.9$ min, the mean field line length is… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.10103v1-abstract-full').style.display = 'inline'; document.getElementById('2001.10103v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2001.10103v1-abstract-full" style="display: none;"> We report the discovery of torsional Alfv茅nic oscillations in solar flares, which modulate the time evolution of the magnetic free energy $E_f(t)$, while the magnetic potential energy $E_p(t)$ is uncorrelated, and the nonpotential energy varies as $E_{np}(t) = E_p + E_f(t)$. The mean observed time period of the torsional oscillations is $P_{obs}=15.1 \pm 3.9$ min, the mean field line length is $L=135\pm35$ Mm, and the mean phase speed is $v_{phase} =315 \pm 120$ km s$^{-1}$, which we interpret as torsional Alfv茅nic waves in flare loops with enhanced electron densities. Most of the torsional oscillations are found to be decay-less, but exhibit a positive or negative trend in the evolution of the free energy, indicating new emerging flux (if positive), magnetic cancellation, or flare energy dissipation (if negative). The time evolution of the free energy has been calculated in this study with the {\sl Vertical-Current Approximation (Version 4) Nonlinear Force-Free Field (VCA4-NLFFF)} code, which incorporates automatically detected coronal loops in the solution and bypasses the non-forcefreeness of the photospheric boundary condition, in contrast to traditional NLFFF codes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.10103v1-abstract-full').style.display = 'none'; document.getElementById('2001.10103v1-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, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">21 pages and 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> (2020), ApJ 891:99 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.08673">arXiv:1909.08673</a> <span> [<a href="https://arxiv.org/pdf/1909.08673">pdf</a>, <a href="https://arxiv.org/ps/1909.08673">ps</a>, <a href="https://arxiv.org/format/1909.08673">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/ab5371">10.3847/1538-4357/ab5371 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Non-Stationary Fast-Driven Self-Organized Criticality in Solar Flares </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> </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="1909.08673v1-abstract-short" style="display: inline;"> The original concept of self-organized criticality (Bak et al.~1987), applied to solar flare statistics (Lu and Hamilton 1991), assumed a slow-driven and stationary flaring rate, which warrants time scale separation (between flare durations and inter-flare waiting times), it reproduces power-law distributions for flare peak fluxes and durations, but predicts an exponential waiting time distributio… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.08673v1-abstract-full').style.display = 'inline'; document.getElementById('1909.08673v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.08673v1-abstract-full" style="display: none;"> The original concept of self-organized criticality (Bak et al.~1987), applied to solar flare statistics (Lu and Hamilton 1991), assumed a slow-driven and stationary flaring rate, which warrants time scale separation (between flare durations and inter-flare waiting times), it reproduces power-law distributions for flare peak fluxes and durations, but predicts an exponential waiting time distribution. In contrast to these classical assumptions we observe: (i) multiple energy dissipation episodes during most flares, (ii) violation of the principle of time scale separation, (iii) a fast-driven and non-stationary flaring rate, (iv) a power law distribution for waiting times $螖t$, with a slope of $伪_{螖t} \approx 2.0$, as predicted from the universal reciprocality between mean flaring rates and mean waiting times; and (v) pulses with rise times and decay times of the dissipated magnetic free energy on time scales of $12\pm6$ min, up to 13 times in long-duration ($\lapprox 4$ hrs) flares. These results are inconsistent with coronal long-term energy storage (Rosner and Vaiana 1978), but require photospheric-chromospheric current injections into the corona. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.08673v1-abstract-full').style.display = 'none'; document.getElementById('1909.08673v1-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 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">19 p, 8 Figs</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.08672">arXiv:1909.08672</a> <span> [<a href="https://arxiv.org/pdf/1909.08672">pdf</a>, <a href="https://arxiv.org/ps/1909.08672">ps</a>, <a href="https://arxiv.org/format/1909.08672">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/ab46c1">10.3847/1538-4357/ab46c1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares. IX. Refined Magnetic Modeling </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> </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="1909.08672v1-abstract-short" style="display: inline;"> A more accurate analytical solution of the {\sl vertical-current approximation nonlinear force-free field (VCA3-NLFFF)} model is presented that includes besides the radial $(B_r)$ and the azimuthal $(B_\varphi)$ magnetic field components a poloidal component $(B_胃 \neq 0)$ also. This new analytical solution is of second-order accuracy in the divergence-freeness condition, and of third-order accura… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.08672v1-abstract-full').style.display = 'inline'; document.getElementById('1909.08672v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.08672v1-abstract-full" style="display: none;"> A more accurate analytical solution of the {\sl vertical-current approximation nonlinear force-free field (VCA3-NLFFF)} model is presented that includes besides the radial $(B_r)$ and the azimuthal $(B_\varphi)$ magnetic field components a poloidal component $(B_胃 \neq 0)$ also. This new analytical solution is of second-order accuracy in the divergence-freeness condition, and of third-order accuracy in the force-freeness condition. We re-analyze the sample of 173 GOES M- and X-class flares observed with the {\sl Atmospheric Imaging Assembly (AIA)} and {\sl Helioseismic and Magnetic Imager (HMI)} onboard the {\sl Solar Dynamics Observatory (SDO)}. The new code reproduces helically twisted loops with a low winding number below the kink instability consistently, avoiding unstable, highly-twisted structures of the Gold-Hoyle flux rope type. The magnetic energies agree within $E_{VCA3}/E_W=0.99\pm0.21$ with the Wiegelmann (W-NLFFF) code. The time evolution of the magnetic field reveals multiple, intermittent energy build-up and releases in most flares, contradicting both the Rosner-Vaiana model (with gradual energy storage in the corona) and the principle of time scale separation ($蟿_{flare} \ll 蟿_{storage}$) postulated in self-organized criticality models. The mean dissipated flare energy is found to amount to $7\%\pm3\%$ of the potential energy, or $60\%\pm26\%$ of the free energy, a result that can be used for predicting flare magnitudes based on the potential field of active regions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.08672v1-abstract-full').style.display = 'none'; document.getElementById('1909.08672v1-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 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">40. p, 13 Figs</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1906.05840">arXiv:1906.05840</a> <span> [<a href="https://arxiv.org/pdf/1906.05840">pdf</a>, <a href="https://arxiv.org/ps/1906.05840">ps</a>, <a href="https://arxiv.org/format/1906.05840">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/ab29f4">10.3847/1538-4357/ab29f4 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Self-Organized Criticality in Solar and Stellar Flares: Are Extreme Events Scale-Free ? </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> </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="1906.05840v1-abstract-short" style="display: inline;"> We search for outliers in extreme events of statistical size distributions of astrophysical data sets, motivated by the {\sl Dragon-King hypothesis} of Sornette (2009), which suggests that the most extreme events in a statistical distribution may belong to a different population, and thus may be generated by a different phyiscal mechanism, in contrast to the strict power law behavior of {\sl self-… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.05840v1-abstract-full').style.display = 'inline'; document.getElementById('1906.05840v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.05840v1-abstract-full" style="display: none;"> We search for outliers in extreme events of statistical size distributions of astrophysical data sets, motivated by the {\sl Dragon-King hypothesis} of Sornette (2009), which suggests that the most extreme events in a statistical distribution may belong to a different population, and thus may be generated by a different phyiscal mechanism, in contrast to the strict power law behavior of {\sl self-organized criticality (SOC)} models. Identifying such disparate outliers is important for space weather predictions. Possible physical mechanisms to produce such outliers could be generated by sympathetic flaring. However, we find that Dragon-King events are not common in solar and stellar flares, identified in 4 out of 25 solar and stellar flare data sets only. Consequently, small, large, and extreme flares are essentially scale-free and can be modeled with a single physical mechanism. In very large data sets ($N \gapprox 10^4$) we find significant deviations from ideal power laws in almost all data sets. Neverthess, the fitted power law slopes constrain physcial scaling laws in terms of flare areas and volumes, which have the highest nonlinearity in their scaling laws. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.05840v1-abstract-full').style.display = 'none'; document.getElementById('1906.05840v1-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 June, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">6 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/1906.05804">arXiv:1906.05804</a> <span> [<a href="https://arxiv.org/pdf/1906.05804">pdf</a>, <a href="https://arxiv.org/ps/1906.05804">ps</a>, <a href="https://arxiv.org/format/1906.05804">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/ab1b39">10.3847/1538-4357/ab1b39 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares: VII. Aerodynamic Drag in Coronal Mass Ejections </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=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="1906.05804v1-abstract-short" style="display: inline;"> The free energy that is dissipated in a magnetic reconnection process of a solar flare, generally accompanied by a coronal mass ejection (CME), has been considered as the ultimate energy source of the global energy budget of solar flares in previous statistical studies. Here we explore the effects of the aerodynamic drag force on CMEs, which supplies additional energy from the slow solar wind to a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.05804v1-abstract-full').style.display = 'inline'; document.getElementById('1906.05804v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.05804v1-abstract-full" style="display: none;"> The free energy that is dissipated in a magnetic reconnection process of a solar flare, generally accompanied by a coronal mass ejection (CME), has been considered as the ultimate energy source of the global energy budget of solar flares in previous statistical studies. Here we explore the effects of the aerodynamic drag force on CMEs, which supplies additional energy from the slow solar wind to a CME event, besides the magnetic energy supply. For this purpose we fit the analytical aerodynamic drag model of Cargill (2004) and Vrsnak et al.~{\bf (2013)} to the height-time profiles $r(t)$ of LASCO/SOHO data in 14,316 CME events observed during the first 8 years (2010-2017) of the SDO era {\bf (ensuring EUV coverage with AIA)}. Our main findings are: (i) a mean solar wind speed of $w=472 \pm 414$ km s$^{-1}$, (ii) a maximum drag-accelerated CME energy of $E_{drag} \lapprox 2 \times 10^{32}$ erg, (iii) a maximum flare-accelerated CME energy of $E_{flare} \lapprox 1.5 \times 10^{33}$ erg; (iv) the ratio of the summed kinetic energies of all flare-accelerated CMEs to the drag-accelerated CMEs amounts to a factor of 4; (v) the inclusion of the drag force slightly lowers the overall energy budget of CME kinetic energies in flares from $\approx 7\%$ to $\approx 4\%$; and (vi) the arrival times of CMEs at Earth can be predicted with an accuracy of $\approx 23\%$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.05804v1-abstract-full').style.display = 'none'; document.getElementById('1906.05804v1-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 June, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">11 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 877:149 (14pp) (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1902.10612">arXiv:1902.10612</a> <span> [<a href="https://arxiv.org/pdf/1902.10612">pdf</a>, <a href="https://arxiv.org/ps/1902.10612">ps</a>, <a href="https://arxiv.org/format/1902.10612">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/ab0b42">10.3847/1538-4357/ab0b42 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Helical Twisting Number and Braiding Linkage Number of Solar Coronal Loops </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> </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="1902.10612v1-abstract-short" style="display: inline;"> Coronal loops in active regions are often characterized by quasi-circular and helically twisted (sigmoidal) geometries, which are consistent with dipolar potential field models in the former case, and with nonlinear force-free field models with vertical currents in the latter case. Alternatively, Parker-type nanoflare models of the solar corona hypothesize that a braiding mechanism operates betwee… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.10612v1-abstract-full').style.display = 'inline'; document.getElementById('1902.10612v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1902.10612v1-abstract-full" style="display: none;"> Coronal loops in active regions are often characterized by quasi-circular and helically twisted (sigmoidal) geometries, which are consistent with dipolar potential field models in the former case, and with nonlinear force-free field models with vertical currents in the latter case. Alternatively, Parker-type nanoflare models of the solar corona hypothesize that a braiding mechanism operates between unresolved loop strands, which is a more complex topological model. In this study we use the vertical-current approximation of a nonpotential magnetic field solution (that fulfills the divergence-free and force-free conditions) to characterize the number of helical turns $N_{twist}$ in twisted coronal loops. We measure the helical twist in 15 active regions observed with AIA and HMI/SDO and find a mean nonpotentiality angle (between the potential and nonpotential field directions) of $渭_{NP} = 15^\circ \pm 3^\circ$. The resulting mean rotational twist angle is $\varphi = 49^\circ \pm 11^\circ$, which corresponds to $N_{twist}=\varphi/360^\circ = 0.14\pm0.03$ turns with respect to the untwisted potential field, with an absolute upper limit of $N_{twist} \lapprox 0.5$, which is far below the kink instability limit of $|N_{twist}| \gapprox 1$. The number of twist turns $N_{twist}$ corresponds to the Gauss linkage number $N_{link}$ in braiding topologies. We conclude that any braided topology (with $|N_{link}| \ge 1$) cannot explain the observed stability of loops in a force-free corona, nor the observed low twist number. Parker-type nanoflaring can thus occur in non-forcefree environments only, such as in the chromosphere and transition region. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.10612v1-abstract-full').style.display = 'none'; document.getElementById('1902.10612v1-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, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">19 pages, 4 Figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophysical journal 874, 131, (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1810.07712">arXiv:1810.07712</a> <span> [<a href="https://arxiv.org/pdf/1810.07712">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/10.1038/s41567-018-0058-3">10.1038/s41567-018-0058-3 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Alfv茅n Wave Dissipation in the Solar Chromosphere </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Grant%2C+S+D+T">S. D. T. Grant</a>, <a href="/search/astro-ph?searchtype=author&query=Jess%2C+D+B">D. B. Jess</a>, <a href="/search/astro-ph?searchtype=author&query=Zaqarashvili%2C+T+V">T. V. Zaqarashvili</a>, <a href="/search/astro-ph?searchtype=author&query=Beck%2C+C">C. Beck</a>, <a href="/search/astro-ph?searchtype=author&query=Socas-Navarro%2C+H">H. Socas-Navarro</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=Keys%2C+P+H">P. H. Keys</a>, <a href="/search/astro-ph?searchtype=author&query=Christian%2C+D+J">D. J. Christian</a>, <a href="/search/astro-ph?searchtype=author&query=Houston%2C+S+J">S. J. Houston</a>, <a href="/search/astro-ph?searchtype=author&query=Hewitt%2C+R+L">R. L. Hewitt</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="1810.07712v1-abstract-short" style="display: inline;"> Magneto-hydrodynamic (MHD) Alfv茅n waves have been a focus of laboratory plasma physics and astrophysics for over half a century. Their unique nature makes them ideal energy transporters, and while the solar atmosphere provides preferential conditions for their existence, direct detection has proved difficult as a result of their evolving and dynamic observational signatures. The viability of Alfv茅… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1810.07712v1-abstract-full').style.display = 'inline'; document.getElementById('1810.07712v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1810.07712v1-abstract-full" style="display: none;"> Magneto-hydrodynamic (MHD) Alfv茅n waves have been a focus of laboratory plasma physics and astrophysics for over half a century. Their unique nature makes them ideal energy transporters, and while the solar atmosphere provides preferential conditions for their existence, direct detection has proved difficult as a result of their evolving and dynamic observational signatures. The viability of Alfv茅n waves as a heating mechanism relies upon the efficient dissipation and thermalization of the wave energy, with direct evidence remaining elusive until now. Here we provide the first observational evidence of Alfv茅n waves heating chromospheric plasma in a sunspot umbra through the formation of shock fronts. The magnetic field configuration of the shock environment, alongside the tangential velocity signatures, distinguish them from conventional umbral flashes. Observed local temperature enhancements of 5% are consistent with the dissipation of mode-converted Alfv茅n waves driven by upwardly propagating magneto-acoustic oscillations, providing an unprecedented insight into the behaviour of Alfv茅n waves in the solar atmosphere and beyond. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1810.07712v1-abstract-full').style.display = 'none'; document.getElementById('1810.07712v1-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 October, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">Letter: 7 pages, 4 figures. Supplementary Material: 22 pages, 10 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Physics, 14, 480-483 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1808.05269">arXiv:1808.05269</a> <span> [<a href="https://arxiv.org/pdf/1808.05269">pdf</a>, <a href="https://arxiv.org/ps/1808.05269">ps</a>, <a href="https://arxiv.org/format/1808.05269">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"> The Minimum Energy Principle Applied to Parker's Coronal Braiding and Nanoflaring Scenario </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">M. J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=van+Ballegooijen%2C+A+A">A. A van Ballegooijen</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="1808.05269v1-abstract-short" style="display: inline;"> Parker's coronal braiding and nanoflaring scenario predicts the development of tangential discontinuities and highly misaligned magnetic field lines, as a consequence of random buffeting of their footpoints due to the action of sub-photospheric convection. The increased stressing of magnetic field lines is thought to become unstable above some critical misalignment angle and to result into local m… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1808.05269v1-abstract-full').style.display = 'inline'; document.getElementById('1808.05269v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1808.05269v1-abstract-full" style="display: none;"> Parker's coronal braiding and nanoflaring scenario predicts the development of tangential discontinuities and highly misaligned magnetic field lines, as a consequence of random buffeting of their footpoints due to the action of sub-photospheric convection. The increased stressing of magnetic field lines is thought to become unstable above some critical misalignment angle and to result into local magnetic reconnection events, which is generally referred to as Parker's `nanoflaring scenario'. In this study we show that the {\sl minimum (magnetic) energy principle} leads to a bifurcation of force-free field solutions for helical twist angles at $|\varphi(t)| = 蟺$, which prevents the build-up of arbitrary large free energies and misalignment angles. The minimum energy principle predicts that neighbored magnetic field lines are almost parallel (with misalignment angles of $螖渭\approx 1.6^\circ-1.8^\circ$), and do not reach a critical misalignment angle prone to nanoflaring. Consequently, no nanoflares are expected in the divergence-free and force-free parts of the solar corona, while they are more likely to occur in the chromosphere and transition region. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1808.05269v1-abstract-full').style.display = 'none'; document.getElementById('1808.05269v1-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, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">16 pages, 6 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/1805.00281">arXiv:1805.00281</a> <span> [<a href="https://arxiv.org/pdf/1805.00281">pdf</a>, <a href="https://arxiv.org/format/1805.00281">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/aac20b">10.3847/1538-4357/aac20b <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Towards a Quantitative Comparison of Magnetic Field Extrapolations and Observed Coronal Loops </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Warren%2C+H+P">Harry P. Warren</a>, <a href="/search/astro-ph?searchtype=author&query=Crump%2C+N+A">Nicholas A. Crump</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=Sun%2C+X">Xudong Sun</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=Wiegelmann%2C+T">Thomas Wiegelmann</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="1805.00281v1-abstract-short" style="display: inline;"> It is widely believed that loops observed in the solar atmosphere trace out magnetic field lines. However, the degree to which magnetic field extrapolations yield field lines that actually do follow loops has yet to be studied systematically. In this paper we apply three different extrapolation techniques - a simple potential model, a NLFF model based on photospheric vector data, and a NLFF model… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.00281v1-abstract-full').style.display = 'inline'; document.getElementById('1805.00281v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1805.00281v1-abstract-full" style="display: none;"> It is widely believed that loops observed in the solar atmosphere trace out magnetic field lines. However, the degree to which magnetic field extrapolations yield field lines that actually do follow loops has yet to be studied systematically. In this paper we apply three different extrapolation techniques - a simple potential model, a NLFF model based on photospheric vector data, and a NLFF model based on forward fitting magnetic sources with vertical currents - to 15 active regions that span a wide range of magnetic conditions. We use a distance metric to assess how well each of these models is able to match field lines to the 12,202 loops traced in coronal images. These distances are typically 1-2". We also compute the misalignment angle between each traced loop and the local magnetic field vector, and find values of 5-12$^\circ$. We find that the NLFF models generally outperform the potential extrapolation on these metrics, although the differences between the different extrapolations are relatively small. The methodology that we employ for this study suggests a number of ways that both the extrapolations and loop identification can be improved. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.00281v1-abstract-full').style.display = 'none'; document.getElementById('1805.00281v1-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, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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 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/1708.03394">arXiv:1708.03394</a> <span> [<a href="https://arxiv.org/pdf/1708.03394">pdf</a>, <a href="https://arxiv.org/format/1708.03394">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/s11214-018-0489-2">10.1007/s11214-018-0489-2 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Order out of Randomness : Self-Organization Processes in Astrophysics </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=Scholkmann%2C+F">Felix Scholkmann</a>, <a href="/search/astro-ph?searchtype=author&query=Bethune%2C+W">William Bethune</a>, <a href="/search/astro-ph?searchtype=author&query=Schmutz%2C+W">Werner Schmutz</a>, <a href="/search/astro-ph?searchtype=author&query=Abramenko%2C+V">Valentina Abramenko</a>, <a href="/search/astro-ph?searchtype=author&query=Cheung%2C+M">Mark Cheung</a>, <a href="/search/astro-ph?searchtype=author&query=Mueller%2C+D">Daniel Mueller</a>, <a href="/search/astro-ph?searchtype=author&query=Benz%2C+A">Arnold Benz</a>, <a href="/search/astro-ph?searchtype=author&query=Kurths%2C+J">Juergen Kurths</a>, <a href="/search/astro-ph?searchtype=author&query=Chernov%2C+G">Guennadi Chernov</a>, <a href="/search/astro-ph?searchtype=author&query=Kritsuk%2C+A+G">Alexei G. Kritsuk</a>, <a href="/search/astro-ph?searchtype=author&query=Scargle%2C+J+D">Jeffrey D. Scargle</a>, <a href="/search/astro-ph?searchtype=author&query=Melatos%2C+A">Andrew Melatos</a>, <a href="/search/astro-ph?searchtype=author&query=Wagoner%2C+R+V">Robert V. Wagoner</a>, <a href="/search/astro-ph?searchtype=author&query=Trimble%2C+V">Virginia Trimble</a>, <a href="/search/astro-ph?searchtype=author&query=Green%2C+W">William Green</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="1708.03394v2-abstract-short" style="display: inline;"> Self-organization is a property of dissipative nonlinear processes that are governed by an internal driver and a positive feedback mechanism, which creates regular geometric and/or temporal patterns and decreases the entropy, in contrast to random processes. Here we investigate for the first time a comprehensive number of 16 self-organization processes that operate in planetary physics, solar phys… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.03394v2-abstract-full').style.display = 'inline'; document.getElementById('1708.03394v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1708.03394v2-abstract-full" style="display: none;"> Self-organization is a property of dissipative nonlinear processes that are governed by an internal driver and a positive feedback mechanism, which creates regular geometric and/or temporal patterns and decreases the entropy, in contrast to random processes. Here we investigate for the first time a comprehensive number of 16 self-organization processes that operate in planetary physics, solar physics, stellar physics, galactic physics, and cosmology. Self-organizing systems create spontaneous {\sl order out of chaos}, during the evolution from an initially disordered system to an ordered stationary system, via quasi-periodic limit-cycle dynamics, harmonic mechanical resonances, or gyromagnetic resonances. The internal driver can be gravity, rotation, thermal pressure, or acceleration of nonthermal particles, while the positive feedback mechanism is often an instability, such as the magneto-rotational instability, the Rayleigh-B茅nard convection instability, turbulence, vortex attraction, magnetic reconnection, plasma condensation, or loss-cone instability. Physical models of astrophysical self-organization processes involve hydrodynamic, MHD, and N-body formulations of Lotka-Volterra equation systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.03394v2-abstract-full').style.display = 'none'; document.getElementById('1708.03394v2-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 December, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">61 pages, 38 Figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Space Science Reviews (2018), Vol. 214: 55 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1707.09291">arXiv:1707.09291</a> <span> [<a href="https://arxiv.org/pdf/1707.09291">pdf</a>, <a href="https://arxiv.org/ps/1707.09291">ps</a>, <a href="https://arxiv.org/format/1707.09291">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"> Statistical Properties of Photospheric Magnetic Elements Observed by SDO/HMI </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Javaherian%2C+M">Mohsen Javaherian</a>, <a href="/search/astro-ph?searchtype=author&query=Safari%2C+H">Hossein Safari</a>, <a href="/search/astro-ph?searchtype=author&query=Dadashi%2C+N">Neda Dadashi</a>, <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">Markus Josef Aschwanden</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="1707.09291v1-abstract-short" style="display: inline;"> Magnetic elements of the solar surface are studied in magnetograms recorded with the high-resolution Solar Dynamics Observatory / Helioseismic and Magnetic Imager . To extract some statistical and physical properties of these elements (e.g., filling factors, magnetic flux, size, lifetimes), the Yet Another Feature Tracking Algorithm (YAFTA), a region-based method, is employed. An area with 400… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1707.09291v1-abstract-full').style.display = 'inline'; document.getElementById('1707.09291v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1707.09291v1-abstract-full" style="display: none;"> Magnetic elements of the solar surface are studied in magnetograms recorded with the high-resolution Solar Dynamics Observatory / Helioseismic and Magnetic Imager . To extract some statistical and physical properties of these elements (e.g., filling factors, magnetic flux, size, lifetimes), the Yet Another Feature Tracking Algorithm (YAFTA), a region-based method, is employed. An area with 400$^{\prime\prime}\times$400$^{\prime\prime}$ was selected to investigate the magnetic characteristics during the year 2011. The correlation coefficient between filling factors of negative and positive polarities is 0.51. A broken power law fit was applied to the frequency distribution of size and flux. Exponents of the power-law distributions for sizes smaller and greater than 16 arcsec$^2$ were found to be -2.24 and -4.04, respectively. The exponents of power$-$law distributions for fluxes smaller and greater than 2.63$\times$10$^{19}$ Mx were found to be -2.11 and -2.51, respectively. The relationship between the size ($S$) and flux ($F$) of elements can be expressed by a power-law behavior in the form of $S\propto F~^{0.69}$. The lifetime and its relationship with the flux and size of quiet-Sun (QS) elements are studied during three days. The code detected patches with lifetimes of about 15 hours, which we call long-duration events. It is found that more than 95\% of the magnetic elements have lifetimes of less than 100 minutes. About 0.05\% of the elements were found with lifetimes of more than 6 hours. The relationships between the size (S), lifetime (T), and the flux (F) for patches in the QS, indicate the power$-$law relationships $S\propto T~^{0.25}$ and $F\propto T~^{0.38}$, respectively. Executing a detrended fluctuation analysis of the time series of new emerged magnetic elements, we find a Hurst exponent of 0.82, which implies long-range temporal correlation in the system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1707.09291v1-abstract-full').style.display = 'none'; document.getElementById('1707.09291v1-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 July, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">20 pages, 17 figures, submitted to Journal of 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/1705.07138">arXiv:1705.07138</a> <span> [<a href="https://arxiv.org/pdf/1705.07138">pdf</a>, <a href="https://arxiv.org/ps/1705.07138">ps</a>, <a href="https://arxiv.org/format/1705.07138">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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/10.3390/galaxies5040056">10.3390/galaxies5040056 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Exoplanet Predictions Based on Harmonic Orbit Resonances </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=Scholkmann%2C+F">Felix Scholkmann</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="1705.07138v1-abstract-short" style="display: inline;"> The current exoplanet database includes 5454 confirmed planets and candidate planets observed with the KEPLER mission. We find 932 planet pairs from which we extract distance and orbital period ratios. While earlier studies used the Titius-Bode law or a generalized version with logarithmic spacing, which both lack a physical model, we employ here the theory of harmonic orbit resonances, which cont… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.07138v1-abstract-full').style.display = 'inline'; document.getElementById('1705.07138v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1705.07138v1-abstract-full" style="display: none;"> The current exoplanet database includes 5454 confirmed planets and candidate planets observed with the KEPLER mission. We find 932 planet pairs from which we extract distance and orbital period ratios. While earlier studies used the Titius-Bode law or a generalized version with logarithmic spacing, which both lack a physical model, we employ here the theory of harmonic orbit resonances, which contains quantized ratios instead, to explain the observed planet distance ratios and to predict undetected exoplanets. We find that the most prevailing harmonic ratios are (2:1), (3:2), and (5:3), in 73\% of the cases, while alternative harmonic ratios of (5:4), (4:3), (5:2), (3:1) occur in 27\% of the other cases. Our orbital predictions includes 171 exoplanets, 2 Jupiter moons, one Saturn moon, 3 Uranus moons, and 4 Neptune moons. The accuracy of the predicted planet distances amounts to a few percent, which fits the data significantly better than the Titius-Bode law or a logarithmic spacing. This information may be useful for targeted exoplanet searches with Kepler data and to estimate the number of live-carrying planets in habitable zones. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.07138v1-abstract-full').style.display = 'none'; document.getElementById('1705.07138v1-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> 19 May, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">9 pages, 7 Figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2017, Galaxies 5(4), 56 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1704.01993">arXiv:1704.01993</a> <span> [<a href="https://arxiv.org/pdf/1704.01993">pdf</a>, <a href="https://arxiv.org/ps/1704.01993">ps</a>, <a href="https://arxiv.org/format/1704.01993">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/aa8952">10.3847/1538-4357/aa8952 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares: VI. Refined Energetics of Coronal Mass Ejections </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> </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="1704.01993v1-abstract-short" style="display: inline;"> In this study we refine a CME model presented in an earlier study on the global energetics of solar flares and associated CMEs, and apply it to all (860) GOES M- and X-class flare events observed during the first 7 years (2010-2016) of the Solar Dynamics Observatory (SDO) mission, which doubles the statistics of the earlier study. The model refinements include: (1) the CME geometry in terms of a 3… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1704.01993v1-abstract-full').style.display = 'inline'; document.getElementById('1704.01993v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1704.01993v1-abstract-full" style="display: none;"> In this study we refine a CME model presented in an earlier study on the global energetics of solar flares and associated CMEs, and apply it to all (860) GOES M- and X-class flare events observed during the first 7 years (2010-2016) of the Solar Dynamics Observatory (SDO) mission, which doubles the statistics of the earlier study. The model refinements include: (1) the CME geometry in terms of a 3D sphere undergoing self-similar adiabatic expansion; (2) the inclusion of solar gravitational deceleration during the acceleration and propagation of the CME, which discriminates eruptive and confined CMEs; (4) a self-consistent relationship between the CME center-of-mass motion detected during EUV dimming and the leading-edge motion observed in white-light coronagraphs; (5) the equi-partition of the CME kinetic and thermal energy; and (6) the Rosner-Tucker-Vaiana (RTV) scaling law. The refined CME model is entirely based on EUV dimming observations (using AIA/SDO data) and complements the traditional white-light scattering model (using LASCO/SOHO data), and both models are independently capable to determine fundamental CME parameters such as the CME mass, speed, and energy. Comparing the two methods we find that: (1) LASCO is less sensitive than AIA in detecting CMEs (in 24$\%$ of the cases); (2) CME masses below $m_{cme} \sim 10^{14}$ g are under-estimated by LASCO; (3) AIA and LASCO masses, speeds, and energy agree closely in the statistical mean after elimination of outliers; (4) the CMEs parameters of the speed $v$, emission measure-weighted flare peak temperature $T_e$, and length scale $L$ are consistent with the following scaling laws (derived from first principles): $v \propto T_e^{1/2}$, $v \propto (m_{cme})^{1/4}$, and $m_{cme} \propto L^2$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1704.01993v1-abstract-full').style.display = 'none'; document.getElementById('1704.01993v1-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, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">31 pages, 10 Figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2017, ApJ 847:27 (19pp) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1701.08181">arXiv:1701.08181</a> <span> [<a href="https://arxiv.org/pdf/1701.08181">pdf</a>, <a href="https://arxiv.org/ps/1701.08181">ps</a>, <a href="https://arxiv.org/format/1701.08181">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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/10.1016/j.newast.2017.08.002">10.1016/j.newast.2017.08.002 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Self-Organizing Systems in Planetary Physics: Harmonic Resonances of Planet and Moon Orbits </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> </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="1701.08181v2-abstract-short" style="display: inline;"> The geometric arrangement of planet and moon orbits into a regularly spaced pattern of distances is the result of a self-organizing system. The positive feedback mechanism that operates a self-organizing system is accomplished by harmonic orbit resonances, leading to long-term stable planet and moon orbits in solar or stellar systems. The distance pattern of planets was originally described by the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.08181v2-abstract-full').style.display = 'inline'; document.getElementById('1701.08181v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1701.08181v2-abstract-full" style="display: none;"> The geometric arrangement of planet and moon orbits into a regularly spaced pattern of distances is the result of a self-organizing system. The positive feedback mechanism that operates a self-organizing system is accomplished by harmonic orbit resonances, leading to long-term stable planet and moon orbits in solar or stellar systems. The distance pattern of planets was originally described by the empirical Titius-Bode law, and by a generalized version with a constant geometric progression factor (corresponding to logarithmic spacing). We find that the orbital periods $T_i$ and planet distances $R_i$ from the Sun are not consistent with logarithmic spacing, but rather follow the quantized scaling $(R_{i+1}/R_i) = (T_{i+1}/T_i)^{2/3} = (H_{i+1}/H_i)^{2/3}$, where the harmonic ratios are given by five dominant resonances, namely $(H_{i+1} : H_{i}) = (3:2), (5:3), (2:1), (5:2), (3:1)$. We find that the orbital period ratios tend to follow the quantized harmonic ratios in increasing order. We apply this harmonic orbit resonance model to the planets and moons in our solar system, and to the exo-planets of 55 Cnc and HD 10180 planetary systems. The model allows us a prediction of missing planets in each planetary system, based on the quasi-regular self-organizing pattern of harmonic orbit resonance zones. We predict 7 (and 4) missing exo-planets around the star 55 Cnc (and HD 10180). The accuracy of the predicted planet and moon distances amounts to a few percents. All analyzed systems are found to have $\approx 10$ resonant zones that can be occupied with planets (or moons) in long-term stable orbits. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.08181v2-abstract-full').style.display = 'none'; document.getElementById('1701.08181v2-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 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 27 January, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">34 pages, 13 Figures, https://doi.org/10.1016/j.newast.2017.08.002</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> New Astronomy 58C, 107-123 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1701.01177">arXiv:1701.01177</a> <span> [<a href="https://arxiv.org/pdf/1701.01177">pdf</a>, <a href="https://arxiv.org/ps/1701.01177">ps</a>, <a href="https://arxiv.org/format/1701.01177">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/aa6b01">10.3847/1538-4357/aa6b01 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Width Distribution of Loops and Strands in the Solar Corona -- Are we Hitting Rock Bottom ? </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=Peter%2C+H">Hard Peter</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="1701.01177v2-abstract-short" style="display: inline;"> In this study we analyze {\sl Atmospheric Imaging Assembly (AIA)} and Hi-C images in order to investigate absolute limits for the finest loop strands. We develop a model of the occurrence-size distribution function of coronal loop widths, characterized by a lower limit of widths $w_{min}$, a peak width $w_p$, a peak occurrence number $n_p$, and a power law slope $a$. Our data analysis includes aut… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.01177v2-abstract-full').style.display = 'inline'; document.getElementById('1701.01177v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1701.01177v2-abstract-full" style="display: none;"> In this study we analyze {\sl Atmospheric Imaging Assembly (AIA)} and Hi-C images in order to investigate absolute limits for the finest loop strands. We develop a model of the occurrence-size distribution function of coronal loop widths, characterized by a lower limit of widths $w_{min}$, a peak width $w_p$, a peak occurrence number $n_p$, and a power law slope $a$. Our data analysis includes automated tracing of curvi-linear features with the OCCULT-2 code, automated sampling of the cross-sectional widths of coronal loops, and fitting of the theoretical size distribution to the observed distribution. With Monte-Carlo simulations and variable pixel sizes $螖x$ we derive a first diagnostic criterion to discriminate whether the loop widths are unresolved $(w_p/螖x \approx 2.5\pm0.2)$, or fully resolved (if $w_p/螖x > 2.7$). For images with resolved loop widths we can apply a second diagnostic criterion that predicts the lower limit of loop widths, $w_{min} \approx 3 (螖x_{crit}-0.37")$ as a function of the critical resolution $螖x_{crit}$. We find that the loop widths are marginally resolved in AIA images, but are fully resolved in Hi-C images, where our model predicts a lower limit of loop widths at $w_{min} \approx 100$ km and a most frequent (peak) value at $w_p \approx 300$ km, in agreement with recent results of Brooks et al. This result agrees with the statistics of photospheric granulation sizes and thus supports coronal heating mechanisms operating on the macroscopic scale of photospheric magneto-convection, rather than nanoflare heating models with unresolved microscopic scales. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.01177v2-abstract-full').style.display = 'none'; document.getElementById('1701.01177v2-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 April, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 January, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">43 pages, 18 Figures, submitted to ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2017, ApJ 80:4 (24pp) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1701.01176">arXiv:1701.01176</a> <span> [<a href="https://arxiv.org/pdf/1701.01176">pdf</a>, <a href="https://arxiv.org/ps/1701.01176">ps</a>, <a href="https://arxiv.org/format/1701.01176">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/10.3847/1538-4357/836/1/17">10.3847/1538-4357/836/1/17 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares: V. Energy Closure in Flares and Coronal Mass Ejections </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=Caspi%2C+A">Amir Caspi</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=Holman%2C+G">Gordon Holman</a>, <a href="/search/astro-ph?searchtype=author&query=Jing%2C+J">Ju Jing</a>, <a href="/search/astro-ph?searchtype=author&query=Kretzschmar%2C+M">Matthieu Kretzschmar</a>, <a href="/search/astro-ph?searchtype=author&query=Kontar%2C+E+P">Eduard P. Kontar</a>, <a href="/search/astro-ph?searchtype=author&query=McTiernan%2C+J+M">James M. McTiernan</a>, <a href="/search/astro-ph?searchtype=author&query=Mewaldt%2C+R+A">Richard A. Mewaldt</a>, <a href="/search/astro-ph?searchtype=author&query=O%27Flannagain%2C+A">Aidan O'Flannagain</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=Ryan%2C+D">Daniel Ryan</a>, <a href="/search/astro-ph?searchtype=author&query=Warren%2C+H+P">Harry P. Warren</a>, <a href="/search/astro-ph?searchtype=author&query=Xu%2C+Y">Yan 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="1701.01176v3-abstract-short" style="display: inline;"> In this study we synthesize the results of four previous studies on the global energetics of solar flares and associated coronal mass ejections (CMEs), which include magnetic, thermal, nonthermal, and CME energies in 399 solar M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission. Our findings are: (1) The sum of the mean nonthermal energy o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.01176v3-abstract-full').style.display = 'inline'; document.getElementById('1701.01176v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1701.01176v3-abstract-full" style="display: none;"> In this study we synthesize the results of four previous studies on the global energetics of solar flares and associated coronal mass ejections (CMEs), which include magnetic, thermal, nonthermal, and CME energies in 399 solar M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission. Our findings are: (1) The sum of the mean nonthermal energy of flare-accelerated particles ($E_{\mathrm{nt}}$), the energy of direct heating ($E_{\mathrm{dir}}$), and the energy in coronal mass ejections ($E_{\mathrm{CME}}$), which are the primary energy dissipation processes in a flare, is found to have a ratio of $(E_{\mathrm{nt}}+E_{\mathrm{dir}}+ E_{\mathrm{CME}})/E_{\mathrm{mag}} = 0.87 \pm 0.18$, compared with the dissipated magnetic free energy $E_{\mathrm{mag}}$, which confirms energy closure within the measurement uncertainties and corroborates the magnetic origin of flares and CMEs; (2) The energy partition of the dissipated magnetic free energy is: $0.51\pm0.17$ in nonthermal energy of $\ge 6$ keV electrons, $0.17\pm0.17$ in nonthermal $\ge 1$ MeV ions, $0.07\pm0.14$ in CMEs, and $0.07\pm0.17$ in direct heating; (3) The thermal energy is almost always less than the nonthermal energy, which is consistent with the thick-target model; (4) The bolometric luminosity in white-light flares is comparable with the thermal energy in soft X-rays (SXR); (5) Solar Energetic Particle (SEP) events carry a fraction $\approx 0.03$ of the CME energy, which is consistent with CME-driven shock acceleration; and (6) The warm-target model predicts a lower limit of the low-energy cutoff at $e_c \approx 6$ keV, based on the mean differential emission measure (DEM) peak temperature of $T_e=8.6$ MK during flares. This work represents the first statistical study that establishes energy closure in solar flare/CME events. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.01176v3-abstract-full').style.display = 'none'; document.getElementById('1701.01176v3-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> 7 February, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 January, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">35 pages, 10 Figures, accepted for publication in The Astrophysical Journal</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, Vol. 836, Issue 1, 17 (17pp); 2017 February 10 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1607.06488">arXiv:1607.06488</a> <span> [<a href="https://arxiv.org/pdf/1607.06488">pdf</a>, <a href="https://arxiv.org/ps/1607.06488">ps</a>, <a href="https://arxiv.org/format/1607.06488">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/832/1/27">10.3847/0004-637X/832/1/27 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares: III. Non thermal Energies </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=Holman%2C+G">Gordon Holman</a>, <a href="/search/astro-ph?searchtype=author&query=O%27Flannagain%2C+A">Aidan O'Flannagain</a>, <a href="/search/astro-ph?searchtype=author&query=Caspi%2C+A">Amir Caspi</a>, <a href="/search/astro-ph?searchtype=author&query=McTiernan%2C+J+M">James M. McTiernan</a>, <a href="/search/astro-ph?searchtype=author&query=Kontar%2C+E">Eduard Kontar</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="1607.06488v2-abstract-short" style="display: inline;"> This study entails the third part of a global flare energetics project, in which Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data of 191 M and X-class flare events from the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission are analyzed. We fit a thermal and a nonthermal component to RHESSI spectra, yielding the temperature of the differential emission measure (DEM) tail, the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1607.06488v2-abstract-full').style.display = 'inline'; document.getElementById('1607.06488v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1607.06488v2-abstract-full" style="display: none;"> This study entails the third part of a global flare energetics project, in which Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data of 191 M and X-class flare events from the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission are analyzed. We fit a thermal and a nonthermal component to RHESSI spectra, yielding the temperature of the differential emission measure (DEM) tail, the nonthermal power law slope and flux, and the thermal/nonthermal cross-over energy $e_{\mathrm{co}}$. From these parameters we calculate the total nonthermal energy $E_{\mathrm{nt}}$ in electrons with two different methods: (i) using the observed cross-over energy $e_{\mathrm{co}}$ as low-energy cutoff, and (ii) using the low-energy cutoff $e_{\mathrm{wt}}$ predicted by the warm thick-target bremsstrahlung model of Kontar et al. {\bf Based on a mean temperature of $T_e=8.6$ MK in active regions we find low-energy cutoff energies of $e_{\mathrm{wt}} =6.2\pm 1.6$ keV for the warm-target model, which is significantly lower than the cross-over energies $e_{\mathrm{co}}=21 \pm 6$ keV. Comparing with the statistics of magnetically dissipated energies $E_{\mathrm{mag}}$ and thermal energies $E_{\mathrm{th}}$ from the two previous studies, we find the following mean (logarithmic) energy ratios with the warm-target model: $E_{\mathrm{nt}} = 0.41 \ E_{\mathrm{mag}}$, $E_{\mathrm{th}} = 0.08 \ E_{\mathrm{mag}}$, and $E_{\mathrm{th}} = 0.15 \ E_{\mathrm{nt}}$. The total dissipated magnetic energy exceeds the thermal energy in 95% and the nonthermal energy in 71% of the flare events, which confirms that magnetic reconnection processes are sufficient to explain flare energies. The nonthermal energy exceeds the thermal energy in 85\% of the events, which largely confirms the warm thick-target model. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1607.06488v2-abstract-full').style.display = 'none'; document.getElementById('1607.06488v2-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, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 July, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">34p, 9 Figs., 1 Table</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, Vol. 832, Issue 1, 27 (20pp); 2016 November 20 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1605.04952">arXiv:1605.04952</a> <span> [<a href="https://arxiv.org/pdf/1605.04952">pdf</a>, <a href="https://arxiv.org/ps/1605.04952">ps</a>, <a href="https://arxiv.org/format/1605.04952">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/831/1/105">10.3847/0004-637X/831/1/105 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares: IV. Coronal Mass Ejection Energetics </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> </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="1605.04952v1-abstract-short" style="display: inline;"> This study entails the fourth part of a global flare energetics project, in which the mass $m_{\mathrm{cme}}$, kinetic energy $E_{\mathrm{kin}}$, and the gravitational potential energy $E_{\mathrm{grav}}$ of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission, using a new method based on the E… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1605.04952v1-abstract-full').style.display = 'inline'; document.getElementById('1605.04952v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1605.04952v1-abstract-full" style="display: none;"> This study entails the fourth part of a global flare energetics project, in which the mass $m_{\mathrm{cme}}$, kinetic energy $E_{\mathrm{kin}}$, and the gravitational potential energy $E_{\mathrm{grav}}$ of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission, using a new method based on the EUV dimming effect. The EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The model derives the evolution of the mean electron density, the emission measure, the bulk plasma expansion velocity, the mass, and the energy in the CME source region. The EUV dimming method is truly complementary to the Thomson scattering method in white light, which probes the CME evolution in the heliosphere at $r > 2 R_{\odot}$, while the EUV dimming method tracks the CME launch in the corona. We compare the CME parameters obtained in white light with the LASCO/C2 coronagraph with those obtained from EUV dimming with the Atmospheric Imaging Assembly (AIA) onboard SDO for all identical events in both data sets. We investigate correlations between CME parameters, the relative timing with flare parameters, frequency occurrence distributions, and the energy partition between magnetic, thermal, nonthermal, and CME energies. CME energies are found to be systematically lower than the dissipated magnetic energies, which is consistent with a magnetic origin of CMEs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1605.04952v1-abstract-full').style.display = 'none'; document.getElementById('1605.04952v1-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> 16 May, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">Text 29 pages, 4 tables, 20 figures (machine-readable file of Table 3 is available on request</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1602.02119">arXiv:1602.02119</a> <span> [<a href="https://arxiv.org/pdf/1602.02119">pdf</a>, <a href="https://arxiv.org/ps/1602.02119">ps</a>, <a href="https://arxiv.org/format/1602.02119">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/826/1/61">10.3847/0004-637X/826/1/61 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Tracing the Chromospheric and Coronal Magnetic Field with AIA, IRIS, IBIS, and ROSA Data </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Aschwanden%2C+M+J">M. J. Aschwanden</a>, <a href="/search/astro-ph?searchtype=author&query=Reardon%2C+K">K. Reardon</a>, <a href="/search/astro-ph?searchtype=author&query=Jess%2C+D">D. Jess</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="1602.02119v1-abstract-short" style="display: inline;"> The aim of this study is to explore the suitability of chromospheric images for magnetic modeling of active regions. We use high-resolution images (0.1") from the Interferometric Bidimensional Spectrometer (IBIS) in the Ca II 8542 A line, the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument in the H-alpha 6563 A line, the Interface Region Imaging Spectrograph (IRIS) in the 2796 A line,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.02119v1-abstract-full').style.display = 'inline'; document.getElementById('1602.02119v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1602.02119v1-abstract-full" style="display: none;"> The aim of this study is to explore the suitability of chromospheric images for magnetic modeling of active regions. We use high-resolution images (0.1") from the Interferometric Bidimensional Spectrometer (IBIS) in the Ca II 8542 A line, the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument in the H-alpha 6563 A line, the Interface Region Imaging Spectrograph (IRIS) in the 2796 A line, and compare non-potential magnetic field models obtained from those chromospheric images with those obtained from images of the Atmospheric Imaging Assembly (AIA) in coronal (171 A, etc.) and in chromospheric (304 A) wavelengths. Curvi-linear structures are automatically traced in those images with the OCCULT-2 code, to which we forward-fitted magnetic field lines computed with the Vertical-Current Approximation Non-Linear Force Free Field (VCA-NLFFF) code. We find that the chromospheric images: (1) reveal crisp curvi-linear structures (fibrils, loop segments, spicules) that are extremely well-suited for constraining magnetic modeling; (2) that these curvi-linear structures are field-aligned with the best-fit solution by a median misalignment angle of ~4-7 deg; (3) the free energy computed from coronal data may underestimate that obtained from cromospheric data by a factor of ~ 2-4, (4) the height range of chromospheric features is confined to h ~ 4000$ km, while coronal features are detected up to h ~ 35,000$ km; and (5) the plasma-beta parameter is beta ~ 10^(-5)-10^(-1) for all traced features. We conclude that chromospheric images reveal important magnetic structures that are complementary to coronal images and need to be included in comprehensive magnetic field models, a quest that is not accomodated in standard NLFFF codes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.02119v1-abstract-full').style.display = 'none'; document.getElementById('1602.02119v1-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 February, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">29 pages, 11 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 826:61 (18 pp), 2016 July 20 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1602.00635">arXiv:1602.00635</a> <span> [<a href="https://arxiv.org/pdf/1602.00635">pdf</a>, <a href="https://arxiv.org/ps/1602.00635">ps</a>, <a href="https://arxiv.org/format/1602.00635">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/10.3847/0067-0049/224/2/25">10.3847/0067-0049/224/2/25 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Vertical Current Approximation Nonlinear Force-Free Field Code - Description, Performance Tests, and Measurements of Magnetic Energies Dissipated in Solar Flares </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> </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="1602.00635v1-abstract-short" style="display: inline;"> In this work we provide an updated description of the Vertical Current Approximation Nonlinear Force-Free Field (VCA-NLFFF) code, which is designed to measure the evolution of the potential, nonpotential, free energies, and the dissipated magnetic energies during solar flares. This code provides a complementary and alternative method to existing traditional NLFFF codes. The chief advantages of the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.00635v1-abstract-full').style.display = 'inline'; document.getElementById('1602.00635v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1602.00635v1-abstract-full" style="display: none;"> In this work we provide an updated description of the Vertical Current Approximation Nonlinear Force-Free Field (VCA-NLFFF) code, which is designed to measure the evolution of the potential, nonpotential, free energies, and the dissipated magnetic energies during solar flares. This code provides a complementary and alternative method to existing traditional NLFFF codes. The chief advantages of the VCA-NLFFF code over traditional NLFFF codes are the circumvention of the unrealistic assumption of a force-free photosphere in the magnetic field extrapolation method, the capability to minimize the misalignment angles between observed coronal loops (or chromospheric fibril structures) and theoretical model field lines, as well as computational speed. In performance tests of the VCA-NLFFF code, by comparing with the NLFFF code of Wiegelmann (2004), we find agreement in the potential, nonpotential, and free energy within a factor of about 1.3, but the Wiegelmann code yields in the average a factor of 2 lower flare energies. The VCA-NLFFF code is found to detect decreases in flare energies in most X, M, and C-class flares. The successful detection of energy decreases during a variety of flares with the VCA-NLFFF code indicates that current-driven twisting and untwisting of the magnetic field is an adequate model to quantify the storage of magnetic energies in active regions and their dissipation during flares. - The VCA-NLFFF code is also publicly available in the Solar SoftWare (SSW). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.00635v1-abstract-full').style.display = 'none'; document.getElementById('1602.00635v1-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 February, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">23 Figures, 50 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal Supplement Series, 224:25 (32pp), 2016 June </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1510.01987">arXiv:1510.01987</a> <span> [<a href="https://arxiv.org/pdf/1510.01987">pdf</a>, <a href="https://arxiv.org/ps/1510.01987">ps</a>, <a href="https://arxiv.org/format/1510.01987">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/814/1/19">10.1088/0004-637X/814/1/19 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Thresholded Power Law Size Distributions of Instabilities in Astrophysics </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> </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="1510.01987v1-abstract-short" style="display: inline;"> Power law-like size distributions are ubiquitous in astrophysical instabilities. There are at least four natural effects that cause deviations from ideal power law size distributions, which we model here in a generalized way: (1) a physical threshold of an instability; (2) incomplete sampling of the smallest events below a threshold $x_0$; (3) contamination by an event-unrelated background $x_b$;… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1510.01987v1-abstract-full').style.display = 'inline'; document.getElementById('1510.01987v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1510.01987v1-abstract-full" style="display: none;"> Power law-like size distributions are ubiquitous in astrophysical instabilities. There are at least four natural effects that cause deviations from ideal power law size distributions, which we model here in a generalized way: (1) a physical threshold of an instability; (2) incomplete sampling of the smallest events below a threshold $x_0$; (3) contamination by an event-unrelated background $x_b$; and (4) truncation effects at the largest events due to a finite system size. These effects can be modeled in simplest terms with a "thresholded power law" distribution function (also called generalized Pareto [type II] or Lomax distribution), $N(x) dx \propto (x+x_0)^{-a} dx$, where $x_0 > 0$ is positive for a threshold effect, while $x_0 < 0$ is negative for background contamination. We analytically derive the functional shape of this thresholded power law distribution function from an exponential-growth evolution model, which produces avalanches only when a disturbance exceeds a critical threshold $x_0$. We apply the thresholded power law distribution function to terrestrial, solar (HXRBS, BATSE, RHESSI), and stellar flare (Kepler) data sets. We find that the thresholded power law model provides an adequate fit to most of the observed data. Major advantages of this model are the automated choice of the power law fitting range, diagnostics of background contamination, physical inastability thresholds, instrumental detection thresholds, and finite system size limits. When testing self-organized criticality models, which predict ideal power laws, we suggest to include these natural truncation effects. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1510.01987v1-abstract-full').style.display = 'none'; document.getElementById('1510.01987v1-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> 7 October, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">42 pages, 16 Figures, accepted for publication in The Astrophysical Journal (2015 Oct 7)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, 814:19 (25pp), 2015 November 20 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1509.07546">arXiv:1509.07546</a> <span> [<a href="https://arxiv.org/pdf/1509.07546">pdf</a>, <a href="https://arxiv.org/ps/1509.07546">ps</a>, <a href="https://arxiv.org/format/1509.07546">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/s11207-015-0790-0">10.1007/s11207-015-0790-0 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Benchmark Test of Differential Emission Measure Codes and Multi-Thermal Energies in Solar Active Regions </p> <p class="authors"> <span class="search-hit">Authors:</span> <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">P. Boerner</a>, <a href="/search/astro-ph?searchtype=author&query=Caspi%2C+A">A. Caspi</a>, <a href="/search/astro-ph?searchtype=author&query=McTiernan%2C+J+M">J. M. McTiernan</a>, <a href="/search/astro-ph?searchtype=author&query=Ryan%2C+D">D. Ryan</a>, <a href="/search/astro-ph?searchtype=author&query=Warren%2C+H+P">H. P. Warren</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="1509.07546v1-abstract-short" style="display: inline;"> We compare the ability of 11 Differential Emission Measure (DEM) forward-fitting and inversion methods to constrain the properties of active regions and solar flares by simulating synthetic data using the instrumental response functions of SDO/AIA, SDO/EVE, RHESSI, and GOES/XRS. The codes include the single-Gaussian DEM, a bi-Gaussian DEM, a fixed-Gaussian DEM, a linear spline DEM, the spatial syn… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1509.07546v1-abstract-full').style.display = 'inline'; document.getElementById('1509.07546v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1509.07546v1-abstract-full" style="display: none;"> We compare the ability of 11 Differential Emission Measure (DEM) forward-fitting and inversion methods to constrain the properties of active regions and solar flares by simulating synthetic data using the instrumental response functions of SDO/AIA, SDO/EVE, RHESSI, and GOES/XRS. The codes include the single-Gaussian DEM, a bi-Gaussian DEM, a fixed-Gaussian DEM, a linear spline DEM, the spatial synthesis DEM, the Monte-Carlo Markov chain DEM, the regularized DEM inversion, the Hinode/XRT method, a polynomial spline DEM, an EVE+GOES, and an EVE+RHESSI method. Averaging the results from all 11 DEM methods, we find the following accuracies in the inversion of physical parameters: the EM-weighted temperature $T_w^{fit}/T_w^{sim}=0.9\pm0.1$, the peak emission measure $EM_p^{fit}/EM_p^{sim}=0.6\pm0.2$, the total emission measure $EM_t^{fit}/EM_t^{sim}=0.8\pm0.3$, and the multi-thermal energies $E_{th}^{fit}/EM_{th}^{sim}=1.2\pm0.4$. We find that the AIA spatial synthesis, the EVE+GOES, and the EVE+RHESSI method yield the most accurate results. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1509.07546v1-abstract-full').style.display = 'none'; document.getElementById('1509.07546v1-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 September, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">33 pages, 10 figures, Solar Physics (in press)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Solar Physics, Vol. 290, Issue 10, pp. 2733-2763; 2015 October 21 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1506.04713">arXiv:1506.04713</a> <span> [<a href="https://arxiv.org/pdf/1506.04713">pdf</a>, <a href="https://arxiv.org/ps/1506.04713">ps</a>, <a href="https://arxiv.org/format/1506.04713">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/s11207-015-0791-z">10.1007/s11207-015-0791-z <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Blind Stereoscopy of the Coronal Magnetic Field </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=Schrijver%2C+C+J">Carolus J. Schrijver</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="1506.04713v1-abstract-short" style="display: inline;"> We test the feasibility of 3D coronal-loop tracing in stereoscopic EUV image pairs, with the ultimate goal of enabling efficient 3D reconstruction of the coronal magnetic field that drives flares and coronal mass ejections (CMEs). We developed an automated code designed to perform triangulation of coronal loops in pairs (or triplets) of EUV images recorded from different perspectives. The automate… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1506.04713v1-abstract-full').style.display = 'inline'; document.getElementById('1506.04713v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1506.04713v1-abstract-full" style="display: none;"> We test the feasibility of 3D coronal-loop tracing in stereoscopic EUV image pairs, with the ultimate goal of enabling efficient 3D reconstruction of the coronal magnetic field that drives flares and coronal mass ejections (CMEs). We developed an automated code designed to perform triangulation of coronal loops in pairs (or triplets) of EUV images recorded from different perspectives. The automated (or blind) stereoscopy code includes three major tasks: (i) automated pattern recognition of coronal loops in EUV images, (ii) automated pairing of corresponding loop patterns from two different aspect angles, and (iii) stereoscopic triangulation of 3D loop coordinates. We perform tests with simulated stereoscopic EUV images and quantify the accuracy of all three procedures. In addition we test the performance of the blind stereoscopy code as a function of the spacecraft-separation angle and as a function of the spatial resolution. We also test the sensitivity to magnetic non-potentiality. The automated code developed here can be used for analysis of existing {\sl Solar TErrestrial RElationship Observatory (STEREO)} data, but primarily serves for a design study of a future mission with dedicated diagnostics of non-potential magnetic fields. For a pixel size of 0.6\arcsec (corresponding to the {\sl Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA)} spatial resolution of 1.4\arcsec), we find an optimum spacecraft-separation angle of $伪_s \approx 5^\circ$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1506.04713v1-abstract-full').style.display = 'none'; document.getElementById('1506.04713v1-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 June, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">Solar Physics (accepted 2015 June 15), 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/1504.03301">arXiv:1504.03301</a> <span> [<a href="https://arxiv.org/pdf/1504.03301">pdf</a>, <a href="https://arxiv.org/ps/1504.03301">ps</a>, <a href="https://arxiv.org/format/1504.03301">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/10.1088/2041-8205/804/1/L20">10.1088/2041-8205/804/1/L20 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Magnetic Energy Dissipation during the 2014 March 29 Solar Flares </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> </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="1504.03301v1-abstract-short" style="display: inline;"> We calculated the time evolution of the free magnetic energy during the 2014-Mar-29 flare (SOL2014-03-29T17:48), the first X-class flare detected by IRIS. The free energy was calculated from the difference between the nonpotential field, constrained by the geometry of observed loop structures, and the potential field. We use AIA/SDO and IRIS images to delineate the geometry of coronal loops in EUV… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1504.03301v1-abstract-full').style.display = 'inline'; document.getElementById('1504.03301v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1504.03301v1-abstract-full" style="display: none;"> We calculated the time evolution of the free magnetic energy during the 2014-Mar-29 flare (SOL2014-03-29T17:48), the first X-class flare detected by IRIS. The free energy was calculated from the difference between the nonpotential field, constrained by the geometry of observed loop structures, and the potential field. We use AIA/SDO and IRIS images to delineate the geometry of coronal loops in EUV wavelengths, as well as to trace magnetic field directions in UV wavelengths in the chromosphere and transition region. We find an identical evolution of the free energy for both the coronal and chromospheric tracers, as well as agreement between AIA and IRIS results, with a peak free energy of $E_{free}(t_{peak}) \approx (45 \pm 2) \times 10^{30}$ erg, which decreases by an amount of $螖E_{free} \approx (29 \pm 3) \times 10^{30}$ erg during the flare decay phase. The consistency of free energies measured from different EUV and UV wavelengths for the first time here, demonstrates that vertical electric currents (manifested in form of helically twisted loops) can be detected and measured from both chromospheric and coronal tracers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1504.03301v1-abstract-full').style.display = 'none'; document.getElementById('1504.03301v1-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 April, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">ApJ Letters (accepted 2015-Apr-10; 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/1502.05941">arXiv:1502.05941</a> <span> [<a href="https://arxiv.org/pdf/1502.05941">pdf</a>, <a href="https://arxiv.org/ps/1502.05941">ps</a>, <a href="https://arxiv.org/format/1502.05941">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/802/1/53">10.1088/0004-637X/802/1/53 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares: II. Thermal Energies </p> <p class="authors"> <span class="search-hit">Authors:</span> <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">P. Boerner</a>, <a href="/search/astro-ph?searchtype=author&query=Ryan%2C+D">D. Ryan</a>, <a href="/search/astro-ph?searchtype=author&query=Caspi%2C+A">A. Caspi</a>, <a href="/search/astro-ph?searchtype=author&query=McTiernan%2C+J+M">J. M. McTiernan</a>, <a href="/search/astro-ph?searchtype=author&query=Warren%2C+H+P">H. P. Warren</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="1502.05941v1-abstract-short" style="display: inline;"> We present the second part of a project on the global energetics of solar flares and CMEs that includes about 400 M- and X-class flares observed with AIA/SDO during the first 3.5 years of its mission. In this Paper II we compute the differential emission measure (DEM) distribution functions and associated multi-thermal energies, using a spatially-synthesized Gaussian DEM forward-fitting method. Th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.05941v1-abstract-full').style.display = 'inline'; document.getElementById('1502.05941v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1502.05941v1-abstract-full" style="display: none;"> We present the second part of a project on the global energetics of solar flares and CMEs that includes about 400 M- and X-class flares observed with AIA/SDO during the first 3.5 years of its mission. In this Paper II we compute the differential emission measure (DEM) distribution functions and associated multi-thermal energies, using a spatially-synthesized Gaussian DEM forward-fitting method. The multi-thermal DEM function yields a significantly higher (by an average factor of $\approx 14$), but more comprehensive (multi-)thermal energy than an isothermal energy estimate from the same AIA data. We find a statistical energy ratio of $E_{th}/E_{diss} \approx 2\%-40\%$ between the multi-thermal energy $E_{th}$ and the magnetically dissipated energy $E_{diss}$, which is an order of magnitude higher than the estimates of Emslie et al.~2012. For the analyzed set of M and X-class flares we find the following physical parameter ranges: $L=10^{8.2}-10^{9.7}$ cm for the length scale of the flare areas, $T_p=10^{5.7}-10^{7.4}$ K for the DEM peak temperature, $T_w=10^{6.8}-10^{7.6}$ K for the emission measure-weighted temperature, $n_p=10^{10.3}-10^{11.8}$ cm$^{-3}$ for the average electron density, $EM_p=10^{47.3}-10^{50.3}$ cm$^{-3}$ for the DEM peak emission measure, and $E_{th}=10^{26.8}-10^{32.0}$ erg for the multi-thermal energies. The deduced multi-thermal energies are consistent with the RTV scaling law $E_{th,RTV} = 7.3 \times 10^{-10} \ T_p^3 L_p^2$, which predicts extremal values of $E_{th,max} \approx 1.5 \times 10^{33}$ erg for the largest flare and $E_{th,min} \approx 1 \times 10^{24}$ erg for the smallest coronal nanoflare. The size distributions of the spatial parameters exhibit powerlaw tails that are consistent with the predictions of the fractal-diffusive self-organized criticality model combined with the RTV scaling law. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.05941v1-abstract-full').style.display = 'none'; document.getElementById('1502.05941v1-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> 20 February, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">Accepted for publication in ApJ, 2015-Feb-18 (in press)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, Vol. 802, Issue 1, 53 (20pp); 2015 March 20 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1410.8013">arXiv:1410.8013</a> <span> [<a href="https://arxiv.org/pdf/1410.8013">pdf</a>, <a href="https://arxiv.org/ps/1410.8013">ps</a>, <a href="https://arxiv.org/format/1410.8013">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/797/1/50">10.1088/0004-637X/797/1/50 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Global Energetics of Solar Flares: I. Magnetic Energies </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=Xu%2C+Y">Yan Xu</a>, <a href="/search/astro-ph?searchtype=author&query=Jing%2C+J">Ju Jing</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="1410.8013v1-abstract-short" style="display: inline;"> We present the first part of a project on the global energetics of solar flares and coronal mass ejections (CMEs) that includes about 400 M- and X-class flares observed with AIA and HMI onboard SDO. We calculate the potential energy, free energy, and the flare-dissipated magnetic energy. We calculate these magnetic parameters using two different NLFFF codes: The COR-NLFFF code uses the line-of-sig… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1410.8013v1-abstract-full').style.display = 'inline'; document.getElementById('1410.8013v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1410.8013v1-abstract-full" style="display: none;"> We present the first part of a project on the global energetics of solar flares and coronal mass ejections (CMEs) that includes about 400 M- and X-class flares observed with AIA and HMI onboard SDO. We calculate the potential energy, free energy, and the flare-dissipated magnetic energy. We calculate these magnetic parameters using two different NLFFF codes: The COR-NLFFF code uses the line-of-sight magnetic field component $B_z$ from HMI to define the potential field, and the 2D coordinates of automatically detected coronal loops in 6 coronal wavelengths from AIA to measure the helical twist of coronal loops caused by vertical currents, while the PHOT-NLFFF code extrapolates the photospheric 3D vector fields. We find agreement between the two codes in the measurement of free energies and dissipated energies within a factor of $ \approx 3$. The size distributions of magnetic parameters exhibit powerlaw slopes that are approximately consistent with the fractal-diffusive self-organized criticality model. The magnetic parameters exhibit scaling laws for the nonpotential energy, $E_{np} \propto E_p^{1.02}$, for the free energy, $E_{free} \propto E_p^{1.7}$ and $E_{free} \propto B_{\varphi}^{1.0} L^{1.5}$, for the dissipated energy, $E_{diss} \propto E_p^{1.6}$ and $E_{diss} \propto E_{free}^{0.9}$, and the energy dissipation volume, $V \propto E_{diss}^{1.2}$. The potential energies vary in the range of $E_p = 1 \times 10^{31} - 4 \times 10^{33}$ erg, while the free energy has a ratio of $E_{free}/E_p \approx 1%-25%$. The Poynting flux amounts to $F_{flare} \approx 5 \times 10^{8} - 10^{10}$ erg cm$^{-2}$ s$^{-1}$ during flares, which averages to $F_{AR} \approx 6 \times 10^6$ erg cm$^{-2}$ s$^{-1}$ during the entire observation period and is comparable with the coronal heating rate requirement in active regions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1410.8013v1-abstract-full').style.display = 'none'; document.getElementById('1410.8013v1-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 October, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">63 pages, 22 Figures, 4 Tables, Paper I of series on "Global Energetics of Solar Flares"</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2014, ApJ 797, 50 (35 pp) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1403.6528">arXiv:1403.6528</a> <span> [<a href="https://arxiv.org/pdf/1403.6528">pdf</a>, <a href="https://arxiv.org/ps/1403.6528">ps</a>, <a href="https://arxiv.org/format/1403.6528">other</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> </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/s11214-014-0054-6">10.1007/s11214-014-0054-6 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> 25 Years of Self-Organized Criticality: Solar and Astrophysics </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=Crosby%2C+N">Norma Crosby</a>, <a href="/search/astro-ph?searchtype=author&query=Dimitropoulou%2C+M">Michaila Dimitropoulou</a>, <a href="/search/astro-ph?searchtype=author&query=Georgoulis%2C+M">Manolis Georgoulis</a>, <a href="/search/astro-ph?searchtype=author&query=Hergarten%2C+S">Stefan Hergarten</a>, <a href="/search/astro-ph?searchtype=author&query=MdAteer%2C+J">James MdAteer</a>, <a href="/search/astro-ph?searchtype=author&query=Milovanov%2C+A+V">Alexander V. Milovanov</a>, <a href="/search/astro-ph?searchtype=author&query=Mineshige%2C+S">Shin Mineshige</a>, <a href="/search/astro-ph?searchtype=author&query=Morales%2C+L">Laura Morales</a>, <a href="/search/astro-ph?searchtype=author&query=Nishizuka%2C+N">Naoto Nishizuka</a>, <a href="/search/astro-ph?searchtype=author&query=Pruessner%2C+G">Gunnar Pruessner</a>, <a href="/search/astro-ph?searchtype=author&query=Sanchez%2C+R">Raul Sanchez</a>, <a href="/search/astro-ph?searchtype=author&query=Sharma%2C+S">Surja Sharma</a>, <a href="/search/astro-ph?searchtype=author&query=Strugarek%2C+A">Antoine Strugarek</a>, <a href="/search/astro-ph?searchtype=author&query=Uritsky%2C+V">Vadim Uritsky</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="1403.6528v1-abstract-short" style="display: inline;"> Shortly after the seminal paper {\sl "Self-Organized Criticality: An explanation of 1/f noise"} by Bak, Tang, and Wiesenfeld (1987), the idea has been applied to solar physics, in {\sl "Avalanches and the Distribution of Solar Flares"} by Lu and Hamilton (1991). In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC conce… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1403.6528v1-abstract-full').style.display = 'inline'; document.getElementById('1403.6528v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1403.6528v1-abstract-full" style="display: none;"> Shortly after the seminal paper {\sl "Self-Organized Criticality: An explanation of 1/f noise"} by Bak, Tang, and Wiesenfeld (1987), the idea has been applied to solar physics, in {\sl "Avalanches and the Distribution of Solar Flares"} by Lu and Hamilton (1991). In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into the numerical SOC toy models, such as the discretization of magneto-hydrodynamics (MHD) processes. The novel applications stimulated also vigorous debates about the discrimination between SOC models, SOC-like, and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC studies from the last 25 years and highlight new trends, open questions, and future challenges, as discussed during two recent ISSI workshops on this theme. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1403.6528v1-abstract-full').style.display = 'none'; document.getElementById('1403.6528v1-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 March, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">139 pages, 28 figures, Review based on ISSI workshops "Self-Organized Criticality and Turbulence" (2012, 2013, Bern, Switzerland)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1402.5340">arXiv:1402.5340</a> <span> [<a href="https://arxiv.org/pdf/1402.5340">pdf</a>, <a href="https://arxiv.org/ps/1402.5340">ps</a>, <a href="https://arxiv.org/format/1402.5340">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/785/1/34">10.1088/0004-637X/785/1/34 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Magnetic Field of Active Region 11158 During the 2011 February 12-17 Flares : Differences between Photospheric Extrapolation and Coronal Forward-Fitting Methods </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=Sun%2C+X">Xudong Sun</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+Y">Yang 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="1402.5340v1-abstract-short" style="display: inline;"> We developed a {\sl coronal non-linear force-free field (COR-NLFFF)} forward-fitting code that fits an approximate {\sl non-linear force-free field (NLFFF)} solution to the observed geometry of automatically traced coronal loops. In contrast to photospheric NLFFF codes, which calculate a magnetic field solution from the constraints of the transverse photospheric field, this new code uses coronal c… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1402.5340v1-abstract-full').style.display = 'inline'; document.getElementById('1402.5340v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1402.5340v1-abstract-full" style="display: none;"> We developed a {\sl coronal non-linear force-free field (COR-NLFFF)} forward-fitting code that fits an approximate {\sl non-linear force-free field (NLFFF)} solution to the observed geometry of automatically traced coronal loops. In contrast to photospheric NLFFF codes, which calculate a magnetic field solution from the constraints of the transverse photospheric field, this new code uses coronal constraints instead, and this way provides important information on systematic errors of each magnetic field calculation method, as well as on the non-forcefreeness in the lower chromosphere. In this study we applied the COR-NLFFF code to active region NOAA 11158, during the time interval of 2011 Feb 12 to 17, which includes an X2.2 GOES-class flare plus 35 M and C-class flares. We calcuated the free magnetic energy with a 6-minute cadence over 5 days. We find good agreement between the two types of codes for the total nonpotential $E_N$ and potential energy $E_P$, but find up to a factor of 4 discrepancy in the free energy $E_{free}=E_N-E_P$, and up to a factor of 10 discrepancy in the decrease of the free energy $螖E_{free}$ during flares. The coronal NLFFF code exhibits a larger time variability, and yields a decrease of free energy during the flare that is sufficient to satisfy the flare energy budget, while the photospheric NLFFF code shows much less time variability and an order of magnitude less free energy decrease during flares. The discrepancy may partly be due to the pre-processing of photospheric vector data, but more likely due to the non-forcefreeness in the lower chromosphere. We conclude that the coronal field cannot be correctly calculated based on photospheric data alone, but requires additional information on coronal loop geometries. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1402.5340v1-abstract-full').style.display = 'none'; document.getElementById('1402.5340v1-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 February, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">17 figures, to oppear in ApJ (2014a</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2014, The Astrophysical Journal 785, 34 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1401.4098">arXiv:1401.4098</a> <span> [<a href="https://arxiv.org/pdf/1401.4098">pdf</a>, <a href="https://arxiv.org/ps/1401.4098">ps</a>, <a href="https://arxiv.org/format/1401.4098">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/s11207-014-0492-z">10.1007/s11207-014-0492-z <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Compatibility of Flare Temperatures Observed with AIA, GOES, and RHESSI </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ryan%2C+D+F">Daniel F. Ryan</a>, <a href="/search/astro-ph?searchtype=author&query=O%27Flannagain%2C+A+M">Aidan M. O'Flannagain</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=Gallagher%2C+P+T">Peter T. Gallagher</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="1401.4098v1-abstract-short" style="display: inline;"> We test the compatibility and biases of multi-thermal flare DEM (differential emission measure) peak temperatures determined with AIA with those determined by GOES and RHESSI using the isothermal assumption. In a set of 149 M- and X-class flares observed during the first two years of the SDO mission, AIA finds DEM peak temperatures at the time of the peak GOES 1-8 A flux to have an average of Tp =… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1401.4098v1-abstract-full').style.display = 'inline'; document.getElementById('1401.4098v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1401.4098v1-abstract-full" style="display: none;"> We test the compatibility and biases of multi-thermal flare DEM (differential emission measure) peak temperatures determined with AIA with those determined by GOES and RHESSI using the isothermal assumption. In a set of 149 M- and X-class flares observed during the first two years of the SDO mission, AIA finds DEM peak temperatures at the time of the peak GOES 1-8 A flux to have an average of Tp = 12.0+/-2.9 MK and Gaussian DEM widths of log10(sigma_T) = 0.50+/-0.13. From GOES observations of the same 149 events, a mean temperature of Tp = 15.6+/-2.4 MK is inferred, which is systematically higher by a factor of TGOES/TAIA = 1.4+/-0.4. We demonstrate that this discrepancy results from the isothermal assumption in the inversion of the GOES filter ratio. From isothermal fits to photon spectra at energies of E ~ 6-12 keV of 61 of these events, RHESSI finds the temperature to be higher still by a factor of TRHESSI/TAIA = 1.9+/-1.0. We find that this is partly a consequence of the isothermal assumption. However, RHESSI is not sensitive to the low-temperature range of the DEM peak, and thus RHESSI samples only the high-temperature tail of the DEM function. This can also contribute to the discrepancy between AIA and RHESSI temperatures. The higher flare temperatures found by GOES and RHESSI imply correspondingly lower emission measures. We conclude that self-consistent flare DEM temperatures and emission measures require simultaneous fitting of EUV (AIA) and soft X-ray (GOES and RHESSI) fluxes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1401.4098v1-abstract-full').style.display = 'none'; document.getElementById('1401.4098v1-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> 16 January, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">Accepted by Solar Physics 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/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/1310.4191">arXiv:1310.4191</a> <span> [<a href="https://arxiv.org/pdf/1310.4191">pdf</a>, <a href="https://arxiv.org/ps/1310.4191">ps</a>, <a href="https://arxiv.org/format/1310.4191">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/782/1/54">10.1088/0004-637X/782/1/54 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Macroscopic Description of a Generalized Self-Organized Criticality System: Astrophysical Applications </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> </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="1310.4191v2-abstract-short" style="display: inline;"> We suggest a generalized definition of self-organized criticality (SOC) systems: SOC is a critical state of a nonlinear energy dissipation system that is slowly and continuously driven towards a critical value of a system-wide instability threshold, producing scale-free, fractal-diffusive, and intermittent avalanches with powerlaw-like size distributions. We develop here a macroscopic description… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.4191v2-abstract-full').style.display = 'inline'; document.getElementById('1310.4191v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1310.4191v2-abstract-full" style="display: none;"> We suggest a generalized definition of self-organized criticality (SOC) systems: SOC is a critical state of a nonlinear energy dissipation system that is slowly and continuously driven towards a critical value of a system-wide instability threshold, producing scale-free, fractal-diffusive, and intermittent avalanches with powerlaw-like size distributions. We develop here a macroscopic description of SOC systems that provides an equivalent description of the complex microscopic fine structure, in terms of fractal-diffusive transport (FD-SOC). Quantitative values for the size distributions of SOC parameters (length scales $L$, time scales $T$, waiting times $螖t$, fluxes $F$, and energies $E$) are derived from first principles, using the scale-free probability conjecture, $N(L) dL \propto L^{-d}$, for Euclidean space dimension $d$. We apply this model to astrophysical SOC systems, such as lunar craters, the asteroid belt, Saturn ring particles, magnetospheric substorms, radiation belt electrons, solar flares, stellar flares, pulsar glitches, soft gamma-ray repeaters, black-hole objects, blazars, and cosmic rays. The FD-SOC model predicts correctly the size distributions of 8 out of these 12 astrophysical phenomena, and indicates non-standard scaling laws and measurement biases for the others. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.4191v2-abstract-full').style.display = 'none'; document.getElementById('1310.4191v2-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 December, 2013; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 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">Journal ref:</span> 2014, The Astrophpysical Journal 782, 54 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1308.5198">arXiv:1308.5198</a> <span> [<a href="https://arxiv.org/pdf/1308.5198">pdf</a>, <a href="https://arxiv.org/ps/1308.5198">ps</a>, <a href="https://arxiv.org/format/1308.5198">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/776/2/132">10.1088/0004-637X/776/2/132 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multi-Wavelength Observations of the Spatio-Temporal Evolution of Solar Flares with AIA/SDO: II. Hydrodynamic Scaling Laws and Thermal Energies </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=Shimizu%2C+T">Toshifumi Shimizu</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="1308.5198v1-abstract-short" style="display: inline;"> In this study we measure physical parameters of the same set of 155 M and X-class solar flares observed with AIA/SDO as analyzed in Paper I, by performing a {\sl differential emission measure (DEM)} analysis to determine the flare peak emission measure $EM_p$, peak temperature $T_p$, electron density $n_p$, and thermal energy $E_{th}$, in addition to the spatial scales $L$, areas $A$, and volumes… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.5198v1-abstract-full').style.display = 'inline'; document.getElementById('1308.5198v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1308.5198v1-abstract-full" style="display: none;"> In this study we measure physical parameters of the same set of 155 M and X-class solar flares observed with AIA/SDO as analyzed in Paper I, by performing a {\sl differential emission measure (DEM)} analysis to determine the flare peak emission measure $EM_p$, peak temperature $T_p$, electron density $n_p$, and thermal energy $E_{th}$, in addition to the spatial scales $L$, areas $A$, and volumes $V$ measured in Paper I. The parameter ranges for M and X-class flares are: $\log(EM_p)=47.0-50.5$, $T_p=5.0-17.8$ MK, $n_p=4 \times 10^9-9 \times 10^{11}$ cm$^{-3}$, and thermal energies of $E_{th}=1.6 \times 10^{28}-1.1 \times 10^{32}$ erg. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law $T_p^2 \propto n_p L$ and $H \propto T^{7/2} L^{-2}$ during the peak time $t_p$ of the flare density $n_p$, when energy balance between the heating rate $H$ and the conductive and radiative loss rates is achieved for a short instant, and thus enables the applicability of the RTV scaling law. The application of the RTV scaling law predicts powerlaw distributions for all physical parameters, which we demonstrate with numerical Monte-Carlo simulations as well as with analytical calculations. A consequence of the RTV law is also that we can retrieve the size distribution of heating rates, for which we find $N(H) \propto H^{-1.8}$, which is consistent with the magnetic flux distribution $N(桅) \propto 桅^{-1.85}$ observed by Parnell et al.(2009) and the heating flux scaling law $F_H \propto H L \propto B/L$ of Schrijver et al.(2004). The fractal-diffusive self-organized criticality model in conjunction with the RTV scaling law reproduces the observed powerlaw distributions and their slopes for all geometrical and physical parameters and can be used to predict the size distributions for other flare datasets, instruments, and detection algorithms. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.5198v1-abstract-full').style.display = 'none'; document.getElementById('1308.5198v1-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 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">The Astrophysics Journal (in press)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> (2013) ApJ 776, 132 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1308.4936">arXiv:1308.4936</a> <span> [<a href="https://arxiv.org/pdf/1308.4936">pdf</a>, <a href="https://arxiv.org/ps/1308.4936">ps</a>, <a href="https://arxiv.org/format/1308.4936">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/775/1/23">10.1088/0004-637X/775/1/23 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multi-Wavelength Observations of the Spatio-Temporal Evolution of Solar Flares with AIA/SDO: I. Universal Scaling Laws of Space and Time Parameters </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=Zhang%2C+J">Jie Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+K">Kai 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="1308.4936v1-abstract-short" style="display: inline;"> We extend a previous statistical solar flare study of 155 GOES M- and X-class flares observed with AIA/SDO (Aschwanden 2012) to all 7 coronal wavelengths (94, 131, 171, 193, 211, 304, 335 \ang) to test the wavelength-dependence of scaling laws and statistical distributions. Except for the 171 and 193 \ang\ wavelengths, which are affected by EUV dimming caused by coronal mass ejections (CMEs), we f… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.4936v1-abstract-full').style.display = 'inline'; document.getElementById('1308.4936v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1308.4936v1-abstract-full" style="display: none;"> We extend a previous statistical solar flare study of 155 GOES M- and X-class flares observed with AIA/SDO (Aschwanden 2012) to all 7 coronal wavelengths (94, 131, 171, 193, 211, 304, 335 \ang) to test the wavelength-dependence of scaling laws and statistical distributions. Except for the 171 and 193 \ang\ wavelengths, which are affected by EUV dimming caused by coronal mass ejections (CMEs), we find near-identical size distributions of geometric (lengths $L$, flare areas $A$, volumes $V$, fractal dimension $D_2$), temporal (flare durations $T$), and spatio-temporal parameters (diffusion coefficient $魏$, spreading exponent $尾$, and maximum expansion velocities $v_{max}$) in different wavelengths, which are consistent with the universal predictions of the fractal-diffusive avalanche model of a slowly-driven self-organized criticality (FD-SOC) system, i.e., $N(L) \propto L^{-3}$, $N(A) \propto A^{-2}$, $N(V) \propto V^{-5/3}$, $N(T) \propto T^{-2}$, $D_2=3/2$, for a Euclidean dimension $d=3$. Empirically we find also a new strong correlation $魏\propto L^{0.94\pm0.01}$ and the 3-parameter scaling law $L \propto 魏 T^{0.1}$, which is more consistent with the logistic-growth model than with classical diffusion. The findings suggest long-range correlation lengths in the FD-SOC system that operate in the vicinity of a critical state, which could be used for predictions of individual extreme events. We find also that eruptive flares (with accompanying CMEs), have larger volumes $V$, longer flare durations $T$, higher EUV and soft X-ray fluxes, and somewhat larger diffusion coefficients $魏$ than confined flares (without CMEs). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1308.4936v1-abstract-full').style.display = 'none'; document.getElementById('1308.4936v1-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> 22 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">(2013) The Astrophysical Journal, Vol. 774 (in press)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> (2013) ApJ 775, 23 </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/1307.5046">arXiv:1307.5046</a> <span> [<a href="https://arxiv.org/pdf/1307.5046">pdf</a>, <a href="https://arxiv.org/ps/1307.5046">ps</a>, <a href="https://arxiv.org/format/1307.5046">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/10.3390/e15083007">10.3390/e15083007 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Optimization of Curvi-Linear Tracing Applied to Solar Physics and Biophysics </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=De+Pontieu%2C+B">Bart De Pontieu</a>, <a href="/search/astro-ph?searchtype=author&query=Katrukha%2C+E+A">Eugene A. Katrukha</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="1307.5046v1-abstract-short" style="display: inline;"> We developed an automated pattern recognition code that is particularly well suited to extract one-dimensional curvi-linear features from two-dimensional digital images. A former version of this {\sl Oriented Coronal CUrved Loop Tracing (OCCULT)} code was applied to spacecraft images of magnetic loops in the solar corona, recorded with the NASA spacecraft {\sl Transition Region And Coronal Explore… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1307.5046v1-abstract-full').style.display = 'inline'; document.getElementById('1307.5046v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1307.5046v1-abstract-full" style="display: none;"> We developed an automated pattern recognition code that is particularly well suited to extract one-dimensional curvi-linear features from two-dimensional digital images. A former version of this {\sl Oriented Coronal CUrved Loop Tracing (OCCULT)} code was applied to spacecraft images of magnetic loops in the solar corona, recorded with the NASA spacecraft {\sl Transition Region And Coronal Explorer (TRACE)} in extreme ultra-violet wavelengths. Here we apply an advanced version of this code ({\sl OCCULT-2}) also to similar images from the {\sl Solar Dynamics Observatory (SDO)}, to chromospheric H-$伪$ images obtained with the {\sl Swedish Solar Telescope (SST)}, and to microscopy images of microtubule filaments in live cells in biophysics. We provide a full analytical description of the code, optimize the control parameters, and compare the automated tracing with visual/manual methods. The traced structures differ by up to 16 orders of magnitude in size, which demonstrates the universality of the tracing algorithm. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1307.5046v1-abstract-full').style.display = 'none'; document.getElementById('1307.5046v1-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 July, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">Entropy, Special Issue on Advanced Signal Processing in Heliospheric Physics, (in press)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2013 Entropy 15(8), 3007-3030 </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> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" 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