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Effects of the crustal magnetic fields on the Martian atmospheric ion escape rate
Author(s) -
Ramstad Robin,
Barabash Stas,
Futaana Yoshifumi,
Nilsson Hans,
Holmström Mats
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl070135
Subject(s) - martian , atmospheric sciences , solar wind , physics , ion , atmospheric escape , flux (metallurgy) , zenith , magnetic field , environmental science , mars exploration program , computational physics , geophysics , astrobiology , materials science , optics , quantum mechanics , metallurgy
Abstract Eight years (2007–2015) of ion flux measurements from Mars Express are used to statistically investigate the influence of the Martian magnetic crustal fields on the atmospheric ion escape rate. We combine all Analyzer of Space Plasmas and Energetic Atoms/Ion Mass Analyzer (ASPERA‐3/IMA) measurements taken during nominal upstream solar wind and solar extreme ultraviolet conditions to compute global average ion distribution functions, individually for the north/south hemispheres and for varying solar zenith angles (SZAs) of the strongest crustal magnetic field. Escape rates are subsequently calculated from each of the average distribution functions. The maximum escape rate (4.2 ± 1.2) × 10 24 s −1 is found for SZA = 60°–80°, while the minimum escape rate (1.7 ± 0.6) × 10 24 s −1 is found for SZA = 28°–60°, showing that the dayside orientation of the crustal fields significantly affects the global escape rate ( p = 97%). However, averaged over time, independent of SZA, we find no statistically significant difference in the escape rates from the two hemispheres (escape from southern hemisphere 46% ± 18% of global rate).