Effects of the non-uniform initial environment and the guide field on the plasmoid instability

TL;DR

This study investigates how non-uniform initial plasma density, temperature, and guide fields influence plasmoid instability in resistive MHD simulations, revealing conditions that suppress or alter the instability and reconnection rates.

Contribution

It provides new insights into the effects of initial plasma conditions and guide fields on plasmoid instability and magnetic reconnection in resistive MHD.

Findings

Higher initial plasma density at the center raises the critical Lundquist number.

Lower plasma beta increases the critical Lundquist number for instability.

Guide field has limited impact on plasmoid instability.

Abstract

Effects of non-uniform initial mass density and temperature on the plasmoid instability are studied via 2.5-dimensional resistive magnetohydrodynamic(MHD) simulations. Our results indicate that the development of the plasmoid instability is apparently prevented when the initial plasma density at the center of the current sheet is higher than that in the upstream region. As a result, the higher the plasma density at the center and the lower the plasma $\beta$ in the upstream region, the higher the critical Lundquist number needed for triggering secondary instabilities. When $\beta =0.2$, the critical Lundquist number is higher than $10^4$. For the same Lundquist number, the magnetic reconnection rate is lower for the lower plasma $\beta$ case. Oppositely, when the initial mass density is uniform and the Lundquist number is low, the magnetic reconnection rate turns out to be higher for the lower plasma $\beta$ case. For the high Lundquist number case ($>10^4$) with uniform initial mass density, the magnetic reconnection is not affected by the initial plasma $\beta$ and the temperature distribution. Our results indicate that the guide field has a limited impact on the plasmoid instability in resistive MHD.