Nature of the heating mechanism for the diffuse solar corona

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The corona is a magnetically dominated environment, consisting of a variety of plasma structures including X-ray bright points, coronal holes and coronal loops. The latter are closed magnetic structures that occur over a range of scales and are anchored at each end in the solar surface. Large-scale regions of diffuse emission are made up of many long coronal loops2. Here we present X-ray observations of the diffuse corona from which we deduce its likely heating mechanism. We find that the observed variation in temperature along a loop is highly sensitive to the spatial distribution of the heating. From a comparison of the observations and models we conclude that uniform heating gives the best fit to the loop temperature distribution, enabling us to eliminate previously suggested mechanisms of low-lying heating near the footpoints of a loop. Our findings favour turbulent breaking and reconnection of magnetic field lines as the heating mechanism of the diffuse solar corona.","datePublished":"","dateModified":"","pageStart":"545","pageEnd":"547","sameAs":"https://doi.org/10.1038/31166","keywords":["Science","Humanities and Social Sciences","multidisciplinary"],"image":["https://media.springernature.com/lw1200/springer-static/image/art%3A10.1038%2F31166/MediaObjects/41586_1998_Article_BF31166_Fig1_HTML.gif","https://media.springernature.com/lw1200/springer-static/image/art%3A10.1038%2F31166/MediaObjects/41586_1998_Article_BF31166_Fig2_HTML.gif","https://media.springernature.com/lw1200/springer-static/image/art%3A10.1038%2F31166/MediaObjects/41586_1998_Article_BF31166_Fig3_HTML.gif"],"isPartOf":{"name":"Nature","issn":["1476-4687","0028-0836"],"volumeNumber":"393","@type":["Periodical","PublicationVolume"]},"publisher":{"name":"Nature Publishing Group UK","logo":{"url":"https://www.springernature.com/app-sn/public/images/logo-springernature.png","@type":"ImageObject"},"@type":"Organization"},"author":[{"name":"E. 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class="c-article-header"> <header> <ul class="c-article-identifiers" data-test="article-identifier"> <li class="c-article-identifiers__item" data-test="article-category">Letter</li> <li class="c-article-identifiers__item">Published: <time datetime="1998-06-11">11 June 1998</time></li> </ul> <h1 class="c-article-title" data-test="article-title" data-article-title="">Nature of the heating mechanism for the diffuse solar corona</h1> <ul class="c-article-author-list c-article-author-list--short" data-test="authors-list" data-component-authors-activator="authors-list"><li class="c-article-author-list__item"><a data-test="author-name" data-track="click" data-track-action="open author" data-track-label="link" href="#auth-E__R_-Priest-Aff1" data-author-popup="auth-E__R_-Priest-Aff1" data-author-search="Priest, E. R." data-corresp-id="c1">E. R. Priest<svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-mail-medium"></use></svg></a><sup class="u-js-hide"><a href="#Aff1">1</a></sup>, </li><li class="c-article-author-list__item"><a data-test="author-name" data-track="click" data-track-action="open author" data-track-label="link" href="#auth-C__R_-Foley-Aff2" data-author-popup="auth-C__R_-Foley-Aff2" data-author-search="Foley, C. R.">C. R. Foley</a><sup class="u-js-hide"><a href="#Aff2">2</a></sup>, </li><li class="c-article-author-list__item c-article-author-list__item--hide-small-screen"><a data-test="author-name" data-track="click" data-track-action="open author" data-track-label="link" href="#auth-J_-Heyvaerts-Aff3" data-author-popup="auth-J_-Heyvaerts-Aff3" data-author-search="Heyvaerts, J.">J. Heyvaerts</a><sup class="u-js-hide"><a href="#Aff3">3</a></sup>, </li><li class="c-article-author-list__item c-article-author-list__item--hide-small-screen"><a data-test="author-name" data-track="click" data-track-action="open author" data-track-label="link" href="#auth-T__D_-Arber-Aff1" data-author-popup="auth-T__D_-Arber-Aff1" data-author-search="Arber, T. D.">T. D. Arber</a><sup class="u-js-hide"><a href="#Aff1">1</a></sup>, </li><li class="c-article-author-list__item c-article-author-list__item--hide-small-screen"><a data-test="author-name" data-track="click" data-track-action="open author" data-track-label="link" href="#auth-J__L_-Culhane-Aff2" data-author-popup="auth-J__L_-Culhane-Aff2" data-author-search="Culhane, J. L.">J. L. Culhane</a><sup class="u-js-hide"><a href="#Aff2">2</a></sup> & </li><li class="c-article-author-list__show-more" aria-label="Show all 6 authors for this article" title="Show all 6 authors for this article">…</li><li class="c-article-author-list__item"><a data-test="author-name" data-track="click" data-track-action="open author" data-track-label="link" href="#auth-L__W_-Acton-Aff4" data-author-popup="auth-L__W_-Acton-Aff4" data-author-search="Acton, L. W.">L. W. Acton</a><sup class="u-js-hide"><a href="#Aff4">4</a></sup> </li></ul><button aria-expanded="false" class="c-article-author-list__button"><svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-chevron-down-medium"></use></svg><span>Show authors</span></button> <p class="c-article-info-details" data-container-section="info"> <a data-test="journal-link" href="/" data-track="click" data-track-action="journal homepage" data-track-category="article body" data-track-label="link"><i data-test="journal-title">Nature</i></a> <b data-test="journal-volume"><span class="u-visually-hidden">volume</span> 393</b>, <span class="u-visually-hidden">pages </span>545–547 (<span data-test="article-publication-year">1998</span>)<a href="#citeas" class="c-article-info-details__cite-as u-hide-print" data-track="click" data-track-action="cite this article" data-track-label="link">Cite this article</a> </p> <div class="c-article-metrics-bar__wrapper u-clear-both"> <ul class="c-article-metrics-bar u-list-reset"> <li class=" c-article-metrics-bar__item" data-test="access-count"> <p class="c-article-metrics-bar__count">754 <span class="c-article-metrics-bar__label">Accesses</span></p> </li> <li class="c-article-metrics-bar__item" data-test="citation-count"> <p class="c-article-metrics-bar__count">147 <span class="c-article-metrics-bar__label">Citations</span></p> </li> <li class="c-article-metrics-bar__item"> <p class="c-article-metrics-bar__details"><a href="/articles/31166/metrics" data-track="click" data-track-action="view metrics" data-track-label="link" rel="nofollow">Metrics <span class="u-visually-hidden">details</span></a></p> </li> </ul> </div> </header> </div> <div class="c-article-body"> <section aria-labelledby="Abs1" data-title="Abstract" lang="en"><div class="c-article-section" id="Abs1-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="Abs1">Abstract</h2><div class="c-article-section__content" id="Abs1-content"><p>The temperature of the Sun's outer atmosphere (the corona) exceeds that of the solar surface by about two orders of magnitude, but the nature of the coronal heating mechanisms has long been a mystery<sup><a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1" title="Ulmschneider, P., Priest, E. R. & Rosner, R. Mechanisms of Chromospheric and Coronal Heating (Springer, Berlin, (1991)." href="/articles/31166#ref-CR1" id="ref-link-section-d210716150e375">1</a></sup>. The corona is a magnetically dominated environment, consisting of a variety of plasma structures including X-ray bright points, coronal holes and coronal loops. The latter are closed magnetic structures that occur over a range of scales and are anchored at each end in the solar surface. Large-scale regions of diffuse emission are made up of many long coronal loops<sup><a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2" title="Culhane, J. L. Yohkoh observations of the solar corona. Adv. Space Res. 19, 1839–1848 (1997)." href="/articles/31166#ref-CR2" id="ref-link-section-d210716150e379">2</a></sup>. Here we present X-ray observations of the diffuse corona from which we deduce its likely heating mechanism. We find that the observed variation in temperature along a loop is highly sensitive to the spatial distribution of the heating. From a comparison of the observations and models we conclude that uniform heating gives the best fit to the loop temperature distribution, enabling us to eliminate previously suggested mechanisms of low-lying heating near the footpoints of a loop. Our findings favour turbulent breaking and reconnection of magnetic field lines as the heating mechanism of the diffuse solar corona.</p></div></div></section> <noscript> <div class="c-nature-box c-nature-box--side " data-component="entitlement-box"> <div class="js-access-button"> <a href="https://wayf.springernature.com?redirect_uri=https%3A%2F%2Fwww.nature.com%2Farticles%2F31166" class="c-article__button" data-test="ra21"> <svg class="u-icon" width="18" height="18" aria-hidden="true" focusable="false"><use href="#icon-institution"></use></svg> <span class="c-article__button-text">Access through your institution</span> </a> </div> <div class="js-buy-button"> <a href="#access-options" class="c-article__button c-article__button--inverted" data-test="ra21"> <span>Buy or subscribe</span> </a> </div> </div> </noscript> <div class="js-context-bar-sticky-point-mobile" data-track-context="article body"> </div> <div class="c-article-access-provider u-mb-32 u-mt-0"> <p 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T. Buckland for helpful suggestions. Part of the work was carried out while one of us (J.L.C.) was a visiting professor at the Institute for Space and Astronautical Science (ISAS) of Japan. C.R.F. was supported by a Research Studentship from PPARC. NASA supported the work of L.W.A. The Yohkoh mission and its continued operation are projects of ISAS in Japan.</p></div></div></section><section aria-labelledby="author-information" data-title="Author information"><div class="c-article-section" id="author-information-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="author-information">Author information</h2><div class="c-article-section__content" id="author-information-content"><h3 class="c-article__sub-heading" id="affiliations">Authors and Affiliations</h3><ol class="c-article-author-affiliation__list"><li id="Aff1"><p class="c-article-author-affiliation__address">Mathematical and Computational Sciences Department, St Andrews University, KY16 9SS, St Andrews, UK</p><p class="c-article-author-affiliation__authors-list">E. R. Priest & T. D. Arber</p></li><li id="Aff2"><p class="c-article-author-affiliation__address">Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, RH5 6NT, Surrey, UK</p><p class="c-article-author-affiliation__authors-list">C. R. Foley & J. L. Culhane</p></li><li id="Aff3"><p class="c-article-author-affiliation__address">Observatoire, 11 Rue de l'Université, F-6700, Strasbourg, France</p><p class="c-article-author-affiliation__authors-list">J. Heyvaerts</p></li><li id="Aff4"><p class="c-article-author-affiliation__address">Physics Department, Montana State University, Bozeman, 59717, Montana, USA</p><p class="c-article-author-affiliation__authors-list">L. W. Acton</p></li></ol><div class="u-js-hide u-hide-print" data-test="author-info"><span class="c-article__sub-heading">Authors</span><ol class="c-article-authors-search u-list-reset"><li id="auth-E__R_-Priest-Aff1"><span class="c-article-authors-search__title u-h3 js-search-name">E. R. Priest</span><div class="c-article-authors-search__list"><div class="c-article-authors-search__item c-article-authors-search__list-item--left"><a href="/search?author=E.%20R.%20Priest" class="c-article-button" data-track="click" data-track-action="author link - publication" data-track-label="link" rel="nofollow">View author publications</a></div><div class="c-article-authors-search__item c-article-authors-search__list-item--right"><p class="search-in-title-js c-article-authors-search__text">You can also search for this author in <span class="c-article-identifiers"><a class="c-article-identifiers__item" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=search&term=E.%20R.%20Priest" data-track="click" data-track-action="author link - pubmed" data-track-label="link" rel="nofollow">PubMed</a><span class="u-hide"> </span><a class="c-article-identifiers__item" href="http://scholar.google.co.uk/scholar?as_q=&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=any&as_sauthors=%22E.%20R.%20Priest%22&as_publication=&as_ylo=&as_yhi=&as_allsubj=all&hl=en" data-track="click" data-track-action="author link - scholar" data-track-label="link" rel="nofollow">Google Scholar</a></span></p></div></div></li><li id="auth-C__R_-Foley-Aff2"><span class="c-article-authors-search__title u-h3 js-search-name">C. 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