Impact of Temperature-dependent resistivity and thermal conduction on plasmoid Instabilities in current sheets in the solar corona

TL;DR

This study uses 2D MHD simulations to show how temperature-dependent resistivity and thermal conduction influence plasmoid instabilities, reconnection rates, and energy release in the solar corona, highlighting their importance in solar eruptions.

Contribution

It demonstrates the significant effects of anisotropic thermal conduction and temperature-dependent magnetic diffusivity on magnetic reconnection in the solar corona, advancing understanding of solar flare dynamics.

Findings

Temperature in current sheets increases over time.

Thermal conduction redistributes heat, affecting reconnection sites.

Temperature-dependent diffusivity enhances reconnection rate.

Abstract

In this paper we investigate, by means of two-dimensional magnetohydrodynamic simulations, the impact of temperature-dependent resistivity and thermal conduction on the development of plasmoid instabilities in reconnecting current sheets in the solar corona. We find that the plasma temperature in the current sheet region increases with time and it becomes greater than that in the inflow region. As secondary magnetic islands appear, the highest temperature is not always found at the reconnection $X$-points, but also inside the secondary islands. One of the effects of anisotropic thermal conduction is to decrease the temperature of the reconnecting $X-$points and transfer the heat into the $O-$points, the plasmoids, where it gets trapped. In the cases with temperature-dependent magnetic diffusivity, $\eta \sim T^{-3/2}$, the decrease in plasma temperature at the $X-$points leads to: (i) increase in the magnetic diffusivity until the characteristic time for magnetic diffusion becomes comparable to that of thermal conduction; (ii) increase in the reconnection rate; and, (iii) more efficient conversion of magnetic energy into thermal energy and kinetic energy of bulk motions. These results provide further explanation of the rapid release of magnetic energy into heat and kinetic energy seen during flares and coronal mass ejections. In this work, we demonstrate that the consideration of anisotropic thermal conduction and Spitzer-type, temperature-dependent magnetic diffusivity, as in the real solar corona, are crucially important for explaining the occurrence of fast reconnection during solar eruptions.