Two-dimensional modeling of the tearing-mode-governed magnetic reconnection in the large-scale current sheet above the two-ribbon flare

TL;DR

This study models magnetic reconnection in solar flares using 2D simulations, revealing tearing mode instability, turbulence, plasmoid dynamics, and termination shocks that contribute to energy dissipation and heating.

Contribution

It provides a detailed 2D simulation of tearing-mode-driven magnetic reconnection in solar flares, highlighting turbulence, plasmoid behavior, and shock effects not previously characterized.

Findings

Tearing mode induces inhomogeneous turbulence and fast reconnection.

Energy spectrum follows a power-law pattern governed by plasmoid dynamics.

Termination shocks significantly contribute to flare loop heating.

Abstract

We attempt to model magnetic reconnection during the two-ribbon flare in the gravitationally stratified solar atmosphere with the Lundquist number of $S=10^6$ using 2D simulations. We found that the tearing mode instability leads to the inhomogeneous turbulence inside the reconnecting current sheet (CS) and invokes the fast phase of reconnection. Fast reconnection brings an extra dissipation of magnetic field which enhances the reconnection rate in an apparent way. The energy spectrum in the CS shows the power-law pattern and the dynamics of plasmoids governs the associated spectral index. We noticed that the energy dissipation occurs at a scale $l_{ko}$ of 100-200~km, and the associated CS thickness ranges from 1500 to 2500~km, which follows the Taylor scale $l_T=l_{ko} S^{1/6}$. The termination shock(TS) appears in the turbulent region above flare loops, which is an important contributor to heating flare loops. Substantial magnetic energy is converted into both kinetic and thermal energies via TS, and the cumulative heating rate is greater than the rate of the kinetic energy transfer. In addition, the turbulence is somehow amplified by TS, of which the amplitude is related to the local geometry of the TS.