The Martian escape rate as a function of upstream solar conditions

Friday, 19 December 2014
Robin Ramstad, Stas Barabash, Yoshifumi Futaana, Hans Nilsson and Mats Holmstrom, IRF Swedish Institute of Space Physics Kiruna, Kiruna, Sweden
We investigate potential factors for influence on the Martian heavy ion escape rate (Q) by integrating Mars Express ASPERA-3/IMA heavy ion flux measurements in the Martian tail, taken at similar (binned) solar wind density (n), velocity (v) and EUV radiation flux (FEUV) upstream conditions. In the best sampled cases, with v and FEUV constrained, we find a statistically significant decrease in heavy ion escape rate with increased solar wind density. An empirical-analytical model for atmospheric escape is developed by fitting calculated escape rates to all sufficiently sampled solar conditions, indicating an overall negative dependence on solar wind density.