MAVEN Observations of the Response of Martian Ionosphere to the Interplanetary Coronal Mass Ejections of March 2015

The Mars Atmosphere and Volatile EvolutioN spacecraft provides an opportunity to observe the response of the Martian upper atmosphere to the passage of interplanetary coronal mass ejections. We study the response of Martian ionosphere to two successive solar disturbances during 3 and 4 March and 8 and 9 March 2015 using the observations from Neutral Gas and Ion Mass Spectrometer and Langmuir Probe and Waves aboard Mars Atmosphere and Volatile EvolutioN. During these events, the ionospheric boundary was significantly lowered. During 3 March the ionopause is seen to be at a lower altitude, compared to that during 8 March. The higher ionopause seen on 8 March could be due to the sustained effect of heating and inflation by the 3 March interplanetary coronal mass ejection event or due to the heating by the enhanced particle precipitation. The comparison of the O+/O 2+ ratio indicates that there is a preferential decrease of O 2+ and a relative enhancement in O+, probably due to increased dissociative recombination and charge exchange as a result of the higher solar wind densities during the 3 March event. Key Points In situ observations of the response of Martian ionosphere to two adjacent solar disturbances show significant differences in the topside ionosphere During both these events, the ionospheric boundary (ionopause‐like density gradient) was observed at lower altitudes, with much lower ionopause on 3 March The comparison of the dayside profiles of O+/O 2+ ratio shows significant enhancement from ∼220 km only on 3 March, indicating preferential removal of O 2+