ANALYSIS OF THE MARTIAN IONOSPHERE AND THERMOSPHERE ENVIRONMENT FROM MEASUREMENTS OF THE ESA MARS EXPRESS SPACECRAFT

摘要

The heating of the thermospheres and the formation of the ionospheres of terrestrial planets like Venus, Earth and Mars are mainly controlled by the solar XUV radiation (0.1 - 100 nm). The current estimates of the Martian exosphere temperature (in the order of about 300-350 K) are based on hydrogen Lyman-alpha measurements. There is much evidence however, that these Enter your paper here exospheric temperature estimates are to high. The reason for that comes mainly from to the fact that hot neutral hydrogen particles may have contaminated the used data. Our study will compare the ionospheric data obtained by the European Mars Express spacecraft currently in orbit around Mars with previous ionospheric data obtained by observations of US and Russian spacecraft. As the various data sets were obtained during different solar activity periods, it is planned to study the behaviour of the dependence between the neutral temperature in the thermosphere obtained from a Chapman ionospheric profile near the ionospheric peak, and the solar 10.7 cm radio flux (F10.7). Further, ionospheric data obtained at higher latitudes will be used as input in studies regarding solar wind plasma interactions, which cause ionospheric clouds and viscous momentum transfer effects related to the loss of water from Mars. The results will then be compared to known observations (measurements of ionospheric profiles, F10.7 flux, and neutral gas temperatures at the exobase level) on Venus. This study will provide important results in the field of comparative planetology as it will help to obtain a good estimate of the Martian exobase temperature which has so far (in contrast to Venus) not been directly measured. This study will furthermore contribute significantly to the overall analysis and understanding of the Mars Express mission data taking into account that the Japanese Nozomi spacecraft (equipped with a mass spectrometer allowing to infer the Martian exosphere temperature) failed. This study is performed in the framework of the Mars Express participation of the Institute for Geophysics Astronomy and Meteorology (IGAM) of the Karl-Franzens University Graz/Austria and the Space Research Institute (IWF) of the Austrian Academy of Sciences.