Prior, C. and Yeates, A. (2016) 'Twisted versus braided magnetic flux ropes in coronal geometry. II. Comparative behaviour.', Astronomy & astrophysics., 591 . A16.
Aims. Sigmoidal structures in the solar corona are commonly associated with magnetic flux ropes whose magnetic field lines are twisted about a mutual axis. Their dynamical evolution is well studied, with sufficient twisting leading to large-scale rotation (writhing) and vertical expansion, possibly leading to ejection. Here, we investigate the behaviour of flux ropes whose field lines have more complex entangled/braided configurations. Our hypothesis is that this internal structure will inhibit the large-scale morphological changes. Additionally, we investigate the influence of the background field within which the rope is embedded. Methods. A technique for generating tubular magnetic fields with arbitrary axial geometry and internal structure, introduced in part I of this study, provides the initial conditions for resistive-MHD simulations. The tubular fields are embedded in a linear force-free background, and we consider various internal structures for the tubular field, including both twisted and braided. These embedded flux ropes are then evolved using a 3D MHD code. Results. Firstly, in a background where twisted flux ropes evolve through the expected non-linear writhing and vertical expansion, we find that flux ropes with sufficiently braided/entangled interiors show no such large-scale changes. Secondly, embedding a twisted flux rope in a background field with a sigmoidal inversion line leads to eventual reversal of the large-scale rotation. Thirdly, in some cases a braided flux rope splits due to reconnection into two twisted flux ropes of opposing chirality – a phenomenon previously observed in cylindrical configurations. Conclusions. Sufficiently complex entanglement of the magnetic field lines within a flux rope can suppress large-scale morphological changes of its axis, with magnetic energy reduced instead through reconnection and expansion. The structure of the background magnetic field can significantly affect the changing morphology of a flux rope.
|Full text:||(AM) Accepted Manuscript|
Download PDF (24655Kb)
|Full text:||(VoR) Version of Record|
Download PDF (60066Kb)
|Publisher Web site:||http://dx.doi.org/10.1051/0004-6361/201528053|
|Publisher statement:||Reproduced with permission from Astronomy & Astrophysics, © ESO|
|Date accepted:||02 March 2016|
|Date deposited:||15 March 2016|
|Date of first online publication:||03 June 2016|
|Date first made open access:||No date available|
Save or Share this output
|Look up in GoogleScholar|