Nonlinear Fast Magnetoacoustic Wave Propagation in the Neighbourhood of a 2D magnetic X-point:Oscillatory Reconnection

JA McLaughlin, Ineke De Moortel, Alan William Hood, C Brady

Research output: Contribution to journalArticlepeer-review

83 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)227-240
Number of pages14
JournalAstronomy & Astrophysics
Volume493
Issue number1
DOIs
Publication statusPublished - Jan 2009

Keywords

  • magnetohydrodynamics (MHD)
  • waves
  • shock waves
  • Sun: corona
  • Sun: magnetic fields
  • Sun: oscillations
  • CORONAL LOOP OSCILLATIONS
  • ALFVEN WAVES
  • NULL POINTS
  • TRANSITION-REGION
  • SOLAR ATMOSPHERE
  • NEUTRAL POINTS
  • LINE
  • PHASE
  • FIELD
  • TRACE

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