DFG-RSF: Erosion of the Martian atmosphere by solar wind scavenging - theory and coordinated Mars Express and MAVEN observations

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DFG-RSF Proposal: This proposal addresses the fundamental question of the ion escape from the atmosphere of Mars forced by the solar wind by analyzing multiple-spacecraft (MEX and MAVEN) and multi-instrument (MaRS, Marsis, ASPERA, LPW, SWIA, MAG, STATIC) data of the Martian space plasma environment. Although a significant progress in our understanding of the Martian space plasma environment was obtained with MEX, the launch of the MAVEN spacecraft provides, for the first time, the unique opportunity to study these processes by the simultaneous monitoring of the solar wind environment by two spacecraft. The solar wind is the main driver for the solar wind-ionosphere-atmosphere coupling. The magnetosphere of Mars is mainly induced by the solar wind and therefore highly variable. Although multiple spacecraft measurements are now a common tool for the study of the Sun-Earth connections, it will open a new era for the investigation of Mars by allowing for the first time to disentangle spatial from temporal variations. This project will (i) conduct a series of comprehensive case studies of simultaneous observations of ion fluxes in different escape channels, (ii) study the dependence of escape fluxes on different controlling factors: variations of solar wind dynamic pressure, interplanetary magnetic field, strong solar events, the crustal magnetic field, (iii) provide a coherent picture how the momentum carried by the solar wind is transferred to the ionosphere, (iv) quantify escape fluxes as a function of the input parameters of the solar wind and the interplanetary magnetic field. The physical problems to be investigated include also the mechanisms responsible for the escape processes in different reservoirs. The project will be performed by the collaborative efforts of the two research groups at Rheinisches Institut für Umweltforschung RIU in Köln, and the Institute of Space Research IKI in Moscow. The team at RIU will focus on the study of the dynamics of the Martian ionosphere using radio-occultation and radar sounding observations performed by Marsis on Mars Express and also on in-situ plasma measurements from both spacecraft. The IKI team will examine theoretical aspects of the interaction between the solar wind and the Mars ionosphere. Only such a combination of data analysis and theoretical modeling can give us a coherent picture of the physical processes in the plasma environment around Mars. A new research unit consisting of these teams plans to realize their accumulated potential to study the processes near Mars on a new higher level. The combination of experimental and theoretical expertise, experience in data analysis and intimate involvement to the experiments on Mars Express and close collaboration with the MAVEN science team put this team in an outstanding position for the study of the space environment near Mars and provides a strong framework for fulfilling the objectives of the proposal.