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Nonlinear fast magnetoacoustic wave propagation in the neighbourhood of a 2D magnetic X-point: oscillatory reconnection

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McLaughlin, J. A., De Moortel, I., Hood, A. W. and Brady, Christopher S.. (2009) Nonlinear fast magnetoacoustic wave propagation in the neighbourhood of a 2D magnetic X-point: oscillatory reconnection. Astronomy & Astrophysics, Vol.493 (No.1). pp. 227-240. ISSN 0004-6361

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Abstract

Context. This paper extends the models of Craig & McClymont ( 1991, ApJ, 371, L41) and McLaughlin & Hood ( 2004, A& A, 420, 1129) to include finite beta and nonlinear effects. Aims. We investigate the nature of nonlinear fast magnetoacoustic waves about a 2D magnetic X-point.

Methods. We solve the compressible and resistive MHD equations using a Lagrangian remap, shock capturing code (Arber et al. 2001, J. Comp. Phys., 171, 151) and consider an initial condition in v x B . (z) over cap (a natural variable of the system).

Results. We observe the formation of both fast and slow oblique magnetic shocks. The nonlinear wave deforms the X-point into a "cusp-like" point which in turn collapses to a current sheet. The system then evolves through a series of horizontal and vertical current sheets, with associated changes in connectivity, i.e. the system exhibits oscillatory reconnection. Our final state is non-potential (but in force balance) due to asymmetric heating from the shocks. Larger amplitudes in our initial condition correspond to larger values of the final current density left in the system.

Conclusions. The inclusion of nonlinear terms introduces several new features to the system that were absent from the linear regime.

Item Type: Journal Article
Subjects: Q Science > QB Astronomy
Divisions: Faculty of Science > Physics
Journal or Publication Title: Astronomy & Astrophysics
Publisher: EDP Sciences
ISSN: 0004-6361
Official Date: January 2009
Volume: Vol.493
Number: No.1
Number of Pages: 14
Page Range: pp. 227-240
Identification Number: 10.1051/0004-6361:200810465
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Restricted or Subscription Access
Funder: Leverhulme Trust (TL), Royal Society, Science and Technology Facilities Council (Great Britain) (STFC) / Scottish Funding Council (SFC) / Science Research Investment Fund (SRIF)
URI: http://wrap.warwick.ac.uk/id/eprint/28774

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