Global MHD Simulation of the Weak Southward IMF Condition for Different Time Resolutions

Kyung Sun Park

doi:10.3389/fspas.2021.758241

Abstract

We performed high-resolution three-dimensional global MHD simulations to determine the impact of weak southward interplanetary magnetic field (IMF) (Bz = −2 nT) and slow solar wind to the Earth’s magnetosphere and ionosphere. We considered two cases of differing, uniform time resolution with the same grid spacing simulation to find any possible differences in the simulation results. The simulation results show that dayside magnetic reconnection and tail reconnection continuously occur even during the weak and steady southward IMF conditions. A plasmoid is generated on closed plasma sheet field lines. Vortices are formed in the inner side of the magnetopause due to the viscous-like interaction, which is strengthened by dayside magnetic reconnection. We estimated the dayside magnetic reconnection which occurred in relation to the electric field at the magnetopause and confirmed that the enhanced electric field is caused by the reconnection and the twisted structure of the electric field is due to the vortex. The simulation results of the magnetic field and the plasma properties show quasi-periodic variations with a period of 9–11 min between the appearances of vortices. Also the peak values of the cross-polar cap potential are both approximately 50 kV, the occurrence time of dayside reconnections are the same, and the polar cap potential patterns are the same in both cases. Thus, there are no significant differences in outcome between the two cases.

Highlights

Dayside magnetic reconnection between the geomagnetic field and the interplanetary magnetic field (IMF) is the most important for understanding the Earth’s magnetosphere dynamics
When the IMF By is nonzero, the dayside reconnection occur at the high-latitude flanks to satisfy the antiparallel field conditions (Park et al, 2006)
The velocity shear could exist at high-latitude deformed plasma flow by the reconnected even high-speed magnetosheath flow

Summary

Introduction

Dayside magnetic reconnection between the geomagnetic field and the interplanetary magnetic field (IMF) is the most important for understanding the Earth’s magnetosphere dynamics. When the IMF By is nonzero, the dayside reconnection occur at the high-latitude flanks to satisfy the antiparallel field conditions (Park et al, 2006).

Results

Conclusion