MHD simulations of three-dimensional Resistive Reconnection in a cylindrical plasma column

TL;DR

This paper presents three-dimensional MHD simulations of magnetic reconnection in cylindrical plasma columns, demonstrating that 3D instabilities lead to fast reconnection rates independent of the Lundquist number, unlike classical models.

Contribution

The study extends previous 2D reconnection models by showing that 3D effects induce rapid reconnection at lower Lundquist numbers, highlighting the importance of three-dimensional instabilities.

Findings

3D instabilities fragment current sheets into filaments

Reconnection rate becomes independent of Lundquist number at S ≈ 10^3

3D effects accelerate magnetic energy dissipation

Abstract

Magnetic reconnection is a plasma phenomenon where a topological rearrangement of magnetic field lines with opposite polarity results in dissipation of magnetic energy into heat, kinetic energy and particle acceleration. Such a phenomenon is considered as an efficient mechanism for energy release in laboratory and astrophysical plasmas. An important question is how to make the process fast enough to account for observed explosive energy releases. The classical model for steady state magnetic reconnection predicts reconnection times scaling as $S^{1/2}$ (where $S$ is the Lundquist number) and yields times scales several order of magnitude larger than the observed ones. Earlier two-dimensional MHD simulations showed that for large Lundquist number the reconnection time becomes independent of $S$ ("fast reconnection" regime) due to the presence of the secondary tearing instability that takes place for $S \gtrsim 1 \times 10^4$. We report on our 3D MHD simulations of magnetic reconnection in a magnetically confined cylindrical plasma column under either a pressure balanced or a force-free equilibrium and compare the results with 2D simulations of a circular current sheet. We find that the 3D instabilities acting on these configurations result in a fragmentation of the initial current sheet in small filaments, leading to enhanced dissipation rate that becomes independent of the Lundquist number already at $S \simeq 1\times 10^3$.