The depletion of the solar wind near Mars

The absorption of the solar wind by the martian atmosphere via charge exchange is investigated for three processes: H⁺+O → H+O⁺, H⁺+H → H+H⁺ and He⁺⁺+He → He⁺+He⁺. It is shown that the first process can lead to a significant depletion of the solar wind in a small region above the subsolar space, while the effect of the other two processes is of minor importance. Further we find that He⁺ ions created by charge exchange play no role in the total He⁺ outflow at Mars. Finally the flux of O⁺ ions is considered and compared with Phobos-2 measurements.