A case study on the interaction between the solar wind and the Martian nightside crustal magnetic field cusp regions

Precipitating super-thermal electrons are an important energy source to maintain the Martian nightside ionosphere, and the configuration of the magnetic fields above the Martian upper atmosphere is the key to determining the pattern of the precipitating super-thermal electron fluxes. To better understand the newly found double-peaked TEC structures in the Martian nightside, high-resolution observations of the magnetic fields and the super-thermal electrons are needed. In this research, we combined observational results from MAVEN/SWEA and MAVEN/MAG in three cases to show the configurations of magnetic fields and plasma environment above the Martian nightside crustal magnetic field cusp regions. It is found that the nightside double-peaked TEC structures may be explained by the existence of the draped magnetic fields above the crustal magnetic field cusp regions, which could leak the solar wind electrons into the Martian upper atmosphere on one side of the cusp regions and interact with the closed crustal magnetic field (i.e., magnetic reconnection) and generate accelerated electrons on the other side of the cusp regions. The photoelectrons from the dayside are also found to play a role in the formation of the double-peaked TEC structures. This study can help to better understand the interaction between the solar wind and the Martian nightside crustal magnetic field cusp regions and may explain the double-peaked TEC structures in the Martian nightside.