Solar wind proton deposition into the Martian atmosphere

The direct impact of solar wind H+ with the planet Mars is calculated using a three-dimensional hybrid particle code. The simulation results show a strong dependence on solar wind velocity and interplanetary magnetic field angle with the solar wind velocity vector. The energy fluxes calculated approach the solar EUV heating rates from photoelectrons and are found to be asymmetric. The heating is also found on the nightside of the planet due to the large ion gyroradii of the incoming solar wind protons. The percentage of solar wind protons lost to the surface of simulation ranged from 3% to 28% depending on the ram presssure of the solar wind. Finally, these results support earlier suggestions that the solar wind may be a significant source of He in the atmosphere of Mars.