A global analysis of the Martian ionosphere revealing the effects of seasons and EUV variations

The ionosphere of Mars is a complex and dynamic region of the atmosphere. The Mars Express orbiter regularly observes the topside ionosphere, but only in a very limited region at any one time. It is very difficult to produce global maps of the ionosphere or investigate its large scale variations because manual analysis is required to determine if the ionosphere is detected in each individual observation. Here we present the results of applying a new custom artificial intelligence based tool to 2,442,165 observations, representing 16.5 years of data from the Mars Advanced Radar for Sub-surface and Ionospheric Sounding instrument, in Active Ionospheric Sounding mode (MARSIS-AIS). This analysis produces global maps showing the extent of the ionosphere and how it responds to changes in solar EUV irradiation. On the deep nightside, detection rates are higher in specific geographical regions, which follow a similar pattern to detections of discrete UV aurora. In the terminator region, from SZA 90◦ to 125◦, ionospheric detection rates decline gradually, indicating that residual illumination and transport contribute to the plasma in this region.