Solar wind interaction with the Martian upper atmosphere: Roles of the variable 3D cold thermosphere and hot oxygen corona

We study the role of the variable 3D thermosphere and exosphere on the Martian ionospheric structure and ion escape rates in the process of the solar wind-Mars interaction. We employ a four-species multifluid MHD (MF-MHD) model to simulate the Martian ionosphere and magnetosphere. The cold thermosphere background is taken from the Mars Global Ionosphere Thermosphere Model (M-GITM) and the hot oxygen exosphere is adopted from the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (AMPS). A total of four cases with the combination of 1D (globally averaged) and 3D thermospheres and exospheres are studied. The ion escape rates calculated by adopting the 1D and 3D neutral atmospheres are similar; however, the latter is in better agreement with observations in terms of the ionospheric density distribution. In addition, our simulations show that the 3D hot oxygen corona plays an important role in preventing planetary molecular ions (O+2 and CO + 2 ) escaping from Mars, mainly resulting from the mass loading of the high-altitude exospheric O ions. The cold thermospheric oxygen atom, however, is demonstrated to be the primary neutral source for O ion escape during the relatively weak solar cycle 24.