Petschek-type reconnection in the high-Lundquist-number regime during nonlinear evolution on the tilt instability. (arXiv:2005.04221v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Baty_H/0/1/0/all/0/1">Hubert Baty</a>
The process of fast magnetic reconnection supported by the formation of
plasmoid chains in the high Lundquist number ($S$) 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 $S ge S_c$ (Baty 2020). A third phase is reached where an
ensuing stochastic time-dependent reconnection regime with a fast time-averaged
rate independent of $S$ 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 $S$ values (typically for $S sim 100 S_c$), 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.
The process of fast magnetic reconnection supported by the formation of
plasmoid chains in the high Lundquist number ($S$) 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 $S ge S_c$ (Baty 2020). A third phase is reached where an
ensuing stochastic time-dependent reconnection regime with a fast time-averaged
rate independent of $S$ 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 $S$ values (typically for $S sim 100 S_c$), 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.
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