Understanding the Transient Layers in the Ionosphere of Mars with Mars Express and MAVEN

Abstract:

The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) aboard ESA’s Mars Express spacecraft has been making observations of the Martian ionosphere since late 2005. One of the more surprising discoveries in the MARSIS data has been the presence of transient layer-like structure in the Martian ionosphere at altitudes near and above 200 km. While the presence of these layers has now been known for years, the addition of the MAVEN spacecraft has provided the first opportunity to advance the understanding of their origin and variation. The combination of MAVEN’s instrument suite and its elliptical orbit allow a variety of factors to be considered. When MAVEN is far from the planet, the SWEA/SWIA package can be combined with the MARSIS observations to correlate variations in the solar wind with their effects on the density and visibility of these layers. On the other hand, when MAVEN is at low altitudes, its Langmuir Probe (LPW) and mass spectrometer (NGIMS) can directly reveal the source of the structures observed from above by MARSIS by measuring the individual densities of the component ions. Periods where the orbits of the two spacecraft cross at close intervals will be particularly useful in comparing these findings. As many of these close-crossings are just beginning to take place, early results of this study will be presented.