Analysis of Two Selected Solar Events in 2011 and 2015 With Mars Express Radio Occultation Data

The temporal behavior of the Martian ionosphere is highly variable due to various dynamic processes including space weather events. Here, we study the effect of solar flares and coronal mass ejections (CMEs) on the Martian ionosphere for two selected solar events in 2011 and 2015, using the publicly available Mars EXpress (MEX) radio occultation (RO) data (MaRS). We developed a data processing software that converts the calibrated Radio Occultation (RO) Doppler data to scientifically valuable atmospheric profiles. Using this software and previously unexplored MaRS observations, the variations in ionospheric parameters (electron density profiles and total electron content (TEC)) are calculated in order to evaluate the ionospheric changes due to solar flares and CMEs. The RO measurements mostly available 1-4 days apart from the peak events, showed no evident change in the TEC nor in the shape of electron density profiles except for a possible gradual decrease in altitude of M2 (main layer) peak density following the arrival of CMEs. To better quantify the effect of solar events on electron density profiles, RO observations near the time of arrival of solar flares and CMEs are crucial. This can be achieved by frequent RO measurements by various Mars orbiters including spacecraft-to-spacecraft measurements assisted by multi-instrument monitoring of the ionosphere. Effects of solar events on electron density are investigated using previously unexplored MaRS data with an in-house developed codeThe effects were observable on Mars's upper atmosphere for several weeks with a gradual decrease in M2 peak altitude for the 2011 eventThe overall trend of measured TEC variations was in accordance with the predictions, with no clear sign of variations due to solar events