Forced magnetic reconnection and plasmoid coalescence: I - MHD Simulations

Abstract

Forced magnetic reconnection, a reconnection event triggered by external perturbation, should be ubiquitous in the solar corona. Energy released during such cases can be much greater than that which was introduced by the perturbation. It is unclear how the properties of the external perturbation and the initial current sheet affect the reconnection region properties, and thereby the reconnection dynamics and energy release profile. We investigate the effect of the form of the external perturbation and initial current sheet on the evolution of the reconnection region and the energy release process. Chiefly we explore the non-linear interactions between multiple, simultaneous perturbations, which represent more realistic scenarios. Future work will use these results in test particle simulations to investigate particle acceleration over multiple reconnection events. Simulations are performed using Lare2d, a 2.5D Lagrangian-remap solver for the visco-resistive MHD equations. The model of forced reconnection is extended to include superpositions of sinusoidal driving disturbances, including localised Gaussian perturbations. A transient perturbation is applied to the boundaries of a region containing a force-free current sheet. The simulation domain is sufficiently wide to allow multiple magnetic islands to form and coalesce. Island coalescence contributes significantly to energy release and involves rapid reconnection. Long wavelength modes in perturbations dominate the evolution, without the presence of which reconnection is either slow, as in the case of short wavelength modes, or the initial current sheet remains stable, as in the case of noise perturbations. Multiple perturbations combine in a highly non-linear manner: reconnection is typically faster than when either disturbance is applied individually, with multiple low-energy events contributing to the same total energy release.

13 pages (including appendix)

References in corpus (5)

• Instability of current sheets and formation of plasmoid chains
• Numerical Tests of Fast Reconnection in Weakly Stochastic Magnetic Fields
• 25 Years of Self-Organized Criticality: Solar and Astrophysics
• Self-generated turbulence in magnetic reconnection
• Extended theory of the Taylor problem in the plasmoid-unstable regime

Cited by in corpus (6)

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• Oscillatory reconnection and waves driven by merging magnetic flux ropes in solar flares
• Merging plasmoids and nanojet-like ejections in a coronal current sheet
• Energy distribution and substructure formation in astrophysical MHD simulations
• The prominence driven forced reconnection in the solar corona and associated plasma dynamics