Petschek-type reconnection in the high-Lundquist-number regime during nonlinear evolution on the tilt instability

May 8, 2020
13 pages
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Abstract: (arXiv)
The process of fast magnetic reconnection supported by the formation of plasmoid chains in the high Lundquist number (SS) regime is investigated using a recently developed adaptive finite-element magnetohydrodynamic (MHD) code. We employ a two-dimensional incompressible model with a set of reduced visco-resistive MHD equations. The tilt instability setup is chosen to provide a three-step mechanism, where two curved current sheets initially form on an Alfv\'enic time scale followed by a second phase of super-Alfv\'enic growth of plasmoid chains for SScS \ge S_c (Baty 2020). A third phase is reached where an ensuing stochastic time-dependent reconnection regime with a fast time-averaged rate independent of SS is obtained. We reveal the multi-scale current structures during magnetic reconnection, where merging events of plasmoids give rise to monster plasmoids with shocks bounding the outflow regions. At high enough SS values (typically for S100ScS \sim 100 S_c), a dynamical Petschek-type reconnection is achieved with pairs of slow-mode shocks emanating from a small central region containing a few plasmoids. Finally, we briefly discuss the relevance of our results to explain the flaring activity in solar corona and internal disruptions in tokamaks.
Note:
  • arXiv admin note: text overlap with arXiv:2003.08660, arXiv:2001.07036
  • magnetic reconnection -magnetohydrodynamics -plasmas -stars: coronae -Sun: flares
  • dimension: 2
  • stability
  • time dependence
  • finite element
  • central region
  • stochastic
  • nonlinear
  • formation
  • structure