Braided magnetic fields: equilibria, relaxation and heating

Pontin, D.I., Candelaresi, S. , Russell, A.J.B. and Hornig, G. (2016) Braided magnetic fields: equilibria, relaxation and heating. Plasma Physics and Controlled Fusion, 58(5), 054008. (doi: 10.1088/0741-3335/58/5/054008)

Abstract

We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling, in the context of testable predictions for the laboratory and their significance for solar coronal heating. We investigate the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity—as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We finish by discussing the properties of the turbulent relaxation and the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor's hypothesis.

• Item Type: Articles
• Additional Information: All the authors acknowledge financial support from the UK’s STFC (grant number ST/K000993).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Candelaresi, Dr Simon
• Authors: Pontin, D.I., Candelaresi, S., Russell, A.J.B., and Hornig, G.
• College/School: College of Science and Engineering > School of Mathematics and Statistics > Mathematics
• Journal Name: Plasma Physics and Controlled Fusion
• Publisher: IOP Publishing
• ISSN: 0741-3335
• ISSN (Online): 1361-6587
• Published Online: 19 April 2016
• Copyright Holders: Copyright © 2016 IOP Publishing Ltd
• First Published: First published in Plasma Physics and Controlled Fusion 58(5): 054008
• Publisher Policy: Reproduced under a Creative Commons License