Effects of the crustal magnetic fields on the Martian atmospheric ion escape rate. Issue 20 (27th October 2016)

• Record Type: Journal Article
• Authors: Ramstad, Robin; Barabash, Stas; Futaana, Yoshifumi; Nilsson, Hans; Holmström, Mats
• Is Part Of: Geophysical research letters. Volume 43:Issue 20(2016)
• Page Start: 10, 574
• Page End: 10, 579
• Publication Date: 2016-10-27
• Subjects: Mars -- escape -- crustal field -- solar wind -- Mars Express -- ASPERA; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL070135
• Languages: English
• ISSNs: 0094-8276

Abstract

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). Key Points: Crustal field dayside orientation (SZA) significantly influences the atmospheric ion escape rate Nightside and terminator orientations show no significant mutual difference in escape rate Hemispherical asymmetry study without SZA constraint indicates that overall influence of crustal fields is small