3-d resistive MHD simulations of magnetic reconnection and the tearing mode instability in current sheets

TL;DR

This paper presents 3D nonlinear MHD simulations of magnetic reconnection via tearing mode instability in current sheets, revealing energy conversion, island dynamics, and turbulence characteristics relevant to astrophysical phenomena.

Contribution

It provides the first detailed comparison between linear theory, Rutherford regime, and numerical simulations of tearing mode in 3D MHD, highlighting energy dissipation and turbulence features.

Findings

Exponential growth of magnetic islands in linear regime

Linear growth of island width in Rutherford regime

Thermal energy dominates over kinetic energy in the current sheet

Abstract

Magnetic reconnection plays a critical role in many astrophysical processes where high energy emission is observed, e.g. particle acceleration, relativistic accretion powered outflows, pulsar winds and probably in dissipation of Poynting flux in GRBs. The magnetic field acts as a reservoir of energy and can dissipate its energy to thermal and kinetic energy via the tearing mode instability. We have performed 3d nonlinear MHD simulations of the tearing mode instability in a current sheet. Results from a temporal stability analysis in both the linear regime and weakly nonlinear (Rutherford) regime are compared to the numerical simulations. We observe magnetic island formation, island merging and oscillation once the instability has saturated. The growth in the linear regime is exponential in agreement with linear theory. In the second, Rutherford regime the island width grows linearly with time. We find that thermal energy produced in the current sheet strongly dominates the kinetic energy. Finally preliminary analysis indicates a P(k) 4.8 power law for the power spectral density which suggests that the tearing mode vortices play a role in setting up an energy cascade.