Dynamics of braided coronal loops

Pontin, D. I.; Wilmot-Smith, A. L.; Hornig, G.; Galsgaard, K.

doi:10.1051/0004-6361/201014544

Cited by 80 publications

(86 citation statements)

References 44 publications

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“…Wilmot-Smith et al [100] and Pontin et al [99] considered the resistive relaxation of a coronal loop consisting of a complex-braided magnetic field in which an instability leads to spontaneous reconnection producing a multitude of tiny nanoflares (figure 2c-e). They conducted three-dimensional MHD experiments in which this initially braided magnetic field (containing just six crossings), formed by slow footpoint motions, is allowed to relax via resistive MHD.…”

Section: (A) Three-dimensional Magnetohydrodynamic Loop Modellingmentioning

confidence: 99%

A contemporary view of coronal heating

Parnell

Moortel

2012

Phil. Trans. R. Soc. A.

204

188

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Determining the heating mechanism (or mechanisms) that causes the outer atmosphere of the Sun, and many other stars, to reach temperatures orders of magnitude higher than their surface temperatures has long been a key problem. For decades, the problem has been known as the coronal heating problem, but it is now clear that 'coronal heating' cannot be treated or explained in isolation and that the heating of the whole solar atmosphere must be studied as a highly coupled system. The magnetic field of the star is known to play a key role, but, despite significant advancements in solar telescopes, computing power and much greater understanding of theoretical mechanisms, the question of which mechanism or mechanisms are the dominant supplier of energy to the chromosphere and corona is still open. Following substantial recent progress, we consider the most likely contenders and discuss the key factors that have made, and still make, determining the actual (coronal) heating mechanism (or mechanisms) so difficult.

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Section: (A) Three-dimensional Magnetohydrodynamic Loop Modellingmentioning

confidence: 99%

A contemporary view of coronal heating

Parnell

Moortel

2012

Phil. Trans. R. Soc. A.

204

188

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“…Taylor relaxation was successful for reversed-field pinches and has since been investigated for other situations, e.g., for the solar corona with applications to coronal heating and microflares. [11][12][13] There are also known examples where the end state is a nonlinear force-free field; [14][15][16] however, redistribution of helicity, although less extensive, is a major feature of those cases as well.…”

Section: Introductionmentioning

confidence: 99%

Evolution of field line helicity during magnetic reconnection

et al. 2015

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We investigate the evolution of field line helicity for magnetic fields that connect two boundaries without null points, with emphasis on localized finite-B magnetic reconnection. Total (relative) magnetic helicity is already recognized as an important topological constraint on magnetohydrodynamic processes. Field line helicity offers further advantages because it preserves all topological information and can distinguish between different magnetic fields with the same total helicity. Magnetic reconnection changes field connectivity and field line helicity reflects these changes; the goal of this paper is to characterize that evolution. We start by deriving the evolution equation for field line helicity and examining its terms, also obtaining a simplified form for cases where dynamics are localized within the domain. The main result, which we support using kinematic examples, is that during localized reconnection in a complex magnetic field, the evolution of field line helicity is dominated by a work-like term that is evaluated at the field line endpoints, namely, the scalar product of the generalized field line velocity and the vector potential. Furthermore, the flux integral of this term over certain areas is very small compared to the integral of the unsigned quantity, which indicates that changes of field line helicity happen in a well-organized pairwise manner. It follows that reconnection is very efficient at redistributing helicity in complex magnetic fields despite having little effect on the total helicity. V C 2015 AIP Publishing LLC.

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“…The complex evolution of these magnetic features on the photosphere may significantly heat the low corona through braiding and reconnection of the magnetic fields connecting them (e.g., Parnell & Galsgaard 2004;Berger & Asgari-Targhi 2009;Pontin et al 2011).…”

Section: Introductionmentioning

confidence: 99%

THE STORAGE AND DISSIPATION OF MAGNETIC ENERGY IN THE QUIET SUN CORONA DETERMINED FROM SDO /HMI MAGNETOGRAMS

Meyer

Sabol

Mackay

et al. 2013

ApJ

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In recent years, higher cadence, higher resolution observations have revealed the quiet-Sun photosphere to be complex and rapidly evolving. Since magnetic fields anchored in the photosphere extend up into the solar corona, it is expected that the small-scale coronal magnetic field exhibits similar complexity. For the first time, the quiet-Sun coronal magnetic field is continuously evolved through a series of non-potential, quasi-static equilibria, deduced from magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, where the photospheric boundary condition which drives the coronal evolution exactly reproduces the observed magnetograms. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. We find that the free magnetic energy built up and stored within the field is sufficient to explain small-scale, impulsive events such as nanoflares. On comparing with coronal images of the same region, the energy storage and dissipation visually reproduces many of the observed features. The results indicate that the complex small-scale magnetic evolution of a large number of magnetic features is a key element in explaining the nature of the solar corona.

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Dynamics of braided coronal loops

Cited by 80 publications

References 44 publications

A contemporary view of coronal heating

A contemporary view of coronal heating

Evolution of field line helicity during magnetic reconnection

THE STORAGE AND DISSIPATION OF MAGNETIC ENERGY IN THE QUIET SUN CORONA DETERMINED FROM SDO /HMI MAGNETOGRAMS

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