Seasonal variation of Martian pick-up ions: Evidence of breathing exosphere

摘要: Abstract The Mars Express (MEX) Ion Mass Analyser (IMA) found that the detection rate of ring-like distribution protons in solar wind outside bow shock to be quite different between orbital summer (around perihelion) and winter aphelion) for four Martian years, while north–south asymmetry is much smaller than perihelion–aphelion difference. Further analyses using eight years MEX/IMA data 2005 2012 has revealed frequency pick-up ions originating from newly ionized exospheric hydrogen with certain flux strongly correlates Sun–Mars distance, which changes approximately every two years. Variation due cycle phase not distinguishable partly because this effect masked by seasonal variation under MEX capability plasma measurements. This finding indicates UV a major on formation ions, but only controlling factor.