The Influence of Interplanetary Magnetic Field Orientations on the Martian Bow Shock and Magnetosheath Magnetic Field

Unlike Earth, Mars lacks a global intrinsic magnetic field but has regional crustal magnetic fields concentrated in its southern hemisphere. This unique configuration leads to distinctive interactions with the solar wind. In this study, we have investigated the influence of the interplanetary magnetic field (IMF) orientation on the Martian bow shock (BS) and the magnetosheath magnetic field, using data from the Mars Atmosphere and Volatile Evolution mission from the years 2014 to 2020. Our results have demonstrated that the IMF orientation can significantly affect the location of the Martian BS and the magnitude of the magnetosheath magnetic field. Compared to nonradial IMF conditions, radial IMF conditions bring the Martian BS closer to the planetary surface. Additionally, under radial IMF conditions, the proportional increase in the magnetic field magnitude from the solar wind to the dayside magnetosheath is smaller, due to the absence of magnetic pileup processes. However, under both nonradial and radial IMF conditions, the proportional increases in the magnetic field magnitude from the solar wind to the terminator and nightside magnetosheath are similar. Moreover, both the Martian BS and the magnetosheath magnetic field magnitude exhibit dawn-dusk and north-south asymmetries. These asymmetries are determined by both the orientation of the IMF and the presence of regional crustal magnetic fields. Our results suggest that the IMF orientation plays a crucial role in the interaction between the solar wind and Mars.