Effective resistivity for magnetohydrodynamic simulation of collisionless magnetic reconnection

TL;DR

This paper introduces an effective resistivity model for collisionless magnetic reconnection that enhances MHD and Hall MHD simulations, aligning them more closely with kinetic simulation results and improving reconnection rate predictions.

Contribution

The paper develops and applies an effective resistivity model to MHD and Hall MHD simulations, capturing electron kinetic effects and improving the accuracy of magnetic reconnection modeling.

Findings

Reconnection rate in MHD increased to ~0.1$B_0v_A$ with the model.

Peak reconnection rate in Hall MHD reached ~0.25$B_0v_A$.

Simulation results matched well with PIC and hybrid models.

Abstract

The electron inertia term and the off-diagonal electron pressure terms are well-known for the frozen-in condition breakdown in collisionless magnetic reconnection, which are naturally kinetic and difficult to be employed in magnetohydrodynamic (MHD) simulations. After considering the shortcomings of MHD and Hall MHD in neglecting the important electron dynamics such as the inertia and the nongyrotropic pressure, the kinetic characteristics of electrons and ions in the diffusion region are studied and an effective resistivity model involving dynamics of charged particles is proposed [Z. W. Ma et al. 2018 Sci. Rep. 8 10521]. The amplitude of the effective resistivity is mainly determined by electrons in most realistic situations with large ion-electron mass ratios. In this work, the effective resistivity model for collisionless magnetic reconnection without the guide field is successfully applied in the 2.5D MHD and Hall MHD simulations, which remarkably improves the simulation results compared with traditional MHD models. For the MHD case, the effective resistivity significantly increased the reconnection rate to the reasonable value of ~0.1$B_0v_A$. For the Hall MHD case with effective resistivity, the peak reconnection rate is ~0.25$B_0v_A$, and the major structures of the reconnecting field and the current sheet agree well with the particle-in-cell (PIC) and hybrid simulations.