Magnetic Braiding and Quasi-Separatrix Layers

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

doi:10.1088/0004-637x/704/2/1288

Cited by 53 publications

(57 citation statements)

References 21 publications

(29 reference statements)

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“…What comes to mind is filamentation by magnetic braiding (Wilmot-Smith et al 2009) or the creation of an enormous amount of small-scale current sheets by the plasmoid instability (Huang & Bhattacharjee 2016). Another way would be that strong shear forces, by distorting a loop of, say 1000 km width, create a drop of the perturbation field of a few meters width, thereby producing an extended, but very thin, current sheet.…”

Section: Discussionmentioning

confidence: 99%

Evidence for Field-parallel Electron Acceleration in Solar Flares

Haerendel

2017

ApJ

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It is proposed that the coincidence of higher brightness and upward electric current observed by Janvier et al. during a flare indicates electron acceleration by field-parallel potential drops sustained by extremely strong fieldaligned currents of the order of 10 4 A m −2 . A consequence of this is the concentration of the currents in sheets with widths of the order of 1 m. The high current density suggests that the field-parallel potential drops are maintained by current-driven anomalous resistivity. The origin of these currents remains a strong challenge for theorists.

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Section: Discussionmentioning

confidence: 99%

Evidence for Field-parallel Electron Acceleration in Solar Flares

Haerendel

2017

ApJ

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“…If Q is know analytically at a given point and the connectivity can be computed, it is easy to derive Q at r c . This is what is used in Wilmot-Smith et al (2009). However for non analytical fields the computation is not as straightforward and several methods can be possibly used to derive Q(r c ).…”

Section: Squashing Degree Estimation Within a 3d Domainmentioning

confidence: 99%

“…Mandrini et al 1997Mandrini et al , 2006Masson et al 2009;Chandra et al 2011). Indeed, QSLs are also preferential sites for electric current build-up (Milano et al 1999;Galsgaard et al 2003;Aulanier et al 2005;Buechner 2006;Pariat et al 2006;Masson et al 2009;Wilmot-Smith et al 2009. Magnetic reconnection develops within QSLs, with the particularity that field line continuously reconnect with their neighboring field lines, leading to an apparent slipping of the field lines (Aulanier et al , 2007Török et al 2009;Masson et al 2009Masson et al , 2011, while classical reconnection at a separatrice is realized in one step.…”

Section: Introductionmentioning

confidence: 99%

Estimation of the squashing degree within a three-dimensional domain

Pariat

Démoulin

2012

A&A

119

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Context. The study of the magnetic topology of magnetic fields aims at determining the key sites for the development of magnetic reconnection. Quasi-separatrix layers (QSLs), regions of strong connectivity gradients, are topological structures where intenseelectric currents preferentially build-up, and where, later on, magnetic reconnection occurs. Aims. QSLs are volumes of intense squashing degree, Q; the field-line invariant quantifying the deformation of elementary flux tubes. QSL are complex and thin three-dimensional (3D) structures difficult to visualize directly. Therefore Q maps, i.e. 2D cuts of the 3D magnetic domain, are a more and more common features used to study QSLs. Methods. We analyze several methods to derive 2D Q maps and discuss their analytical and numerical properties. These methods can also be used to compute Q within the 3D domain. Results. We demonstrate that while analytically equivalent, the numerical implementation of these methods can be significantly different. We derive the analytical formula and the best numerical methodology that should be used to compute Q inside the 3D domain. We illustrate this method with two twisted magnetic configurations: a theoretical case and a non-linear force free configuration derived from observations. Conclusions. The representation of QSL through 2D planar cuts is an efficient procedure to derive the geometry of these structures and to relate them with other quantities, e.g. electric currents and plasma flows. It will enforce a more direct comparison of the role of QSL in magnetic reconnection.

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“…Regions of high Q outline QSLs. As discussed in Wilmot-Smith et al (2009b), the braided magnetic field taken as the initial state here contains several QSLs. Contours of the squashing factor, Q, in the central plane (z = 0) are shown in Fig.…”

Section: Predictors Of Current Layersmentioning

confidence: 99%

Dynamics of braided coronal loops

Wilmot-Smith¹,

Pontin²,

Hornig³

2010

A&A

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Aims. The response of the solar coronal magnetic field to small-scale photospheric boundary motions including the possible formation of current sheets via the Parker scenario is one of open questions of solar physics. Here we address the problem via a numerical simulation. Methods. The three-dimensional evolution of a braided magnetic field which is initially close to a force-free state is followed using a resistive MHD code. Results. A long-wavelength instability takes place and leads to the formation of two thin current layers. Magnetic reconnection occurs across the current sheets with three-dimensional features shown, including an elliptic magnetic field structure about the reconnection site, and results in an untwisting of the global field structure.

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Magnetic Braiding and Quasi-Separatrix Layers

Cited by 53 publications

References 21 publications

Evidence for Field-parallel Electron Acceleration in Solar Flares

Evidence for Field-parallel Electron Acceleration in Solar Flares

Estimation of the squashing degree within a three-dimensional domain

Dynamics of braided coronal loops

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