Martian hydrogen exosphere charge exchange with solar wind

Abstract

Charge exchange of solar wind with the Martian exosphere has been shown to play a crucial role in the formation of the magnetic pileup boundary observed by Mars Global Surveyor. However, the question of how the Martian exospheric structure is quantitatively altered by charge exchange of the solar wind remains open. To answer this question, a three‐dimensional Monte Carlo exosphere model was developed. In this model the effects of planetary rotation, photoionization, Lyman α scattering, and charge exchange with the solar wind are included. Although the change of exospheric density profile is indistinctive, simulation results show that the existence of the hot atomic hydrogen population produced by charge exchange alters the exospheric temperature structure greatly and the symmetry of the exospheric structure is totally destroyed at high altitude. Another noticeable phenomenon is that charge exchange and Lyman α scattering combine to make the nightside exosphere be cooler than and expand more slowly than the ambient exosphere. In the end we use our simulation results to estimate the contribution of the hot component to Ly α emission. Furthermore, output of our model can be used to predict particle observations made by future missions to Mars.