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 ma gnetic field angle with the solar wind velocity vector. The energy flu xes calculated approach the solar EUV heating rates from photoelectron s and are found to be asymmetric. The heating is also found on the nig htside of the planet due to the large ion gyroradii of the incoming so lar wind protons. The percentage of solar wind protons lost to the sur face of simulation ranged from 3% to 28% depending on the ram presssur e of the solar wind. Finally, these results support earlier suggestion s that the solar wind may be a significant source of He in the atmosph ere of Mars.