Boosting Magnetic Reconnection by Viscosity and Thermal Conduction

TL;DR

This study uses magnetohydrodynamic simulations to show that viscosity and thermal conduction significantly influence magnetic reconnection rates, highlighting the importance of Prandtl numbers in plasma dynamics.

Contribution

It demonstrates how viscosity and thermal conduction, characterized by Prandtl numbers, can enhance magnetic reconnection beyond traditional resistive models.

Findings

Viscosity exceeding resistivity creates broader vortices that facilitate flux transfer.

Reconnection rate increases with viscosity when thermal conduction effectively removes heat.

Controlling Prandtl numbers is crucial for managing reconnection processes.

Abstract

Nonlinear evolution of magnetic reconnection is investigated by means of magnetohydrodynamic simulations including uniform resistivity, uniform viscosity, and anisotropic thermal conduction. When viscosity exceeds resistivity (the magnetic Prandtl number Prm > 1), the viscous dissipation dominates outflow dynamics and leads to the decrease in the plasma density inside a current sheet. The low-density current sheet supports the excitation of the vortex. The thickness of the vortex is broader than that of the current for Prm > 1. The broader vortex flow more efficiently carries the upstream magnetic flux toward the reconnection region, and consequently boosts the reconnection. The reconnection rate increases with viscosity provided that thermal conduction is fast enough to take away the thermal energy increased by the viscous dissipation (the fluid Prandtl number Pr < 1). The result suggests the need to control the Prandtl numbers for the reconnection against the conventional resistive model.