Data-Model Comparison Investigations of Thermospheric Density and Composition Influences on High-Altitude Photoelectron Fluxes at Mars

We present results from a superthermal electron transport code adapted for the Mars environment to study the controlling factors of high-altitude/escaped photoelectron fluxes at this planet. In addition to numerical checks of the code, we investigate the influences of the following effects: magnetic field configuration, solar EUV flux input, and atmospheric density/temperature profiles. In particular, we explore the causes of the extremely high photoelectron fluxes, resulting into two linear dependent trends on solar EUV proxy, measured by the Mars Global Surveyor MAGnetometer/Electron Reflector (MGS MAG/ER) in late 2001-early 2002 (Mars year 25). Studies have shown the relation between these high fluxes and the global dust storm that occurred in the same time period. This modeling work further explores the physical explanations of this relation. Our preliminary results suggest that an increase in CO2 density in the upper thermosphere (150-300 km altitude) is necessary to match the observed changes in photoelectron flux at the MGS altitude of ~400 km.