The Onset of Magnetic Reconnection in Dynamically Evolving Current Sheets

TL;DR

This study uses 3D MHD simulations to investigate when magnetic reconnection begins in evolving solar coronal current sheets, revealing that the tearing instability's onset depends on dynamic thinning and magnetic shear.

Contribution

First 3D MHD simulation analysis of magnetic reconnection onset in dynamically evolving coronal current sheets, highlighting the role of growth time and magnetic shear.

Findings

Reconnection onset occurs after the tearing instability growth time surpasses the thinning time.

Magnetic shear acts as a switch parameter influencing reconnection.

Results suggest observable current sheet properties can predict energy release events.

Abstract

We present the first results of three-dimensional (3D) numerical magnetohydrodynamic (MHD) simulations of the onset of magnetic reconnection via the tearing instability in dynamically thinning current sheets in the solar corona. In all our simulations, the onset of the non-linear tearing instability, which leads to the break-up of the thinning current sheet, does not occur until after the instability growth time becomes faster than the dynamic thinning time. Furthermore, as in previous 3D MHD simulations of static current sheets in the corona, for some parameters, the amount of magnetic shear is a fundamental switch-on parameter, which has consequences for coronal heating models. These results open up the possibility of using observable quantities of coronal current sheets to predict when they will break-up and release magnetic energy to power various energetic phenomena and/or heat the atmosphere.