The Solar Wind-Ionosphere-Thermosphere Coupling at Mars: Combined Data Analysis of Mars Express and MAVEN Observations.

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The variability of the Sun’s electromagnetic radiation and energetic particle output strongly affects the state of the Martian thermosphere. The solar radiation is the main driver of the thermospheric photo-chemistry. The solar ultra-violet and infra-red flux components (< 800 nm) are responsible for the thermospheric heating, while the EUV (5–95 nm) and soft solar X-ray (0.1–5 nm) provide the energy for the formation of the ionosphere by photo-ionization and electron impact. The absence of a global magnetic field at Mars leads to the direct interaction of the solar wind with the planetary ionosphere/neutral atmosphere and therefore to a strong coupling between these domains. Planetary waves, tides, and gravity waves, which are propagating upward from the lower to the upper atmosphere, are other powerful reservoirs for the deposition of energy in the upper mesosphere and thermosphere. The combination of Mars Express and MAVEN instrument observations provides the unique opportunity for a detailed investigation of the temporal and spatial response of the coupling of the ionosphere and thermosphere. Simultaneous observations of the solar variability (e.g. the solar X-ray and EUV flux, solar wind conditions and solar energetic particle flux) at Mars by instruments on both spacecraft in combination with detailed observation of the atmospheric/ionospheric characteristics will give deep insights into the flow of the solar energy throughout the strongly interconnected atmospheric system.We propose a dual-spacecraft (Mars Express and MAVEN) and multi-instrument data analysis of the solar wind/ionosphere/thermosphere coupling at Mars. This project shall conduct a series of comprehensive case studies of simultaneous observations of ions and neutrals in the thermosphere/ionosphere, investigate the relationship between the ion and neutral densities (temperatures) and potential controlling factors: variations of the solar wind dynamic pressure, the solar irradiance and the interplanetary magnetic field, shall study effects of the ionospheric wind dynamo driven by the different types of thermospheric waves. The project will be performed by the Rheinisches Institut für Umweltforschung an der Universität zu Köln, RIU, in collaboration with the Max Planck Institute for Solar System Research MPS in Göttingen. The combination of experimental and theoretical expertise, high experience in data analysis and exclusive involvement with experiments on Mars Express (PI and Co-I-ships) and the close collaboration with the MAVEN science team put this project in an outstanding position for the study of solar wind/ionosphere/thermosphere coupling at Mars.