1,2,2,2,4,5,7,6,1,11,- 1University of Leicester, Leicester, United Kingdom of Great Britain – England, Scotland, Wales (katerina.strg@leicester.ac.uk)
- 2Swedish Institute of Space Physics (IRF), Uppsala, Sweden
- 3Space Sciences Laboratory, University of California, Berkeley, CA, USA
- 4Department of Astronomy, University of Maryland, College Park, MD, USA
- 5Planetary Magnetospheres Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
- 6Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA
- 7Swedish Institute of Space Physics (IRF), Kiruna, Sweden
- 8Department of Physics and Astronomy, West Virginia University, Morgantown, WV, USA
- 9Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, CA, USA
- 10Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
- 11IRAP, CNRS-UPS-CNES, Toulouse, France
- 12INAF, Rome, Italy
The nightside ionosphere of Mars is formed by plasma transport from the dayside and electron precipitation. Significant progress has been made in our understanding of its composition and structure at low altitudes. However, what happens at higher altitudes remains unclear. Plasma structures escaping from the nightside of Mars could reveal the plasma transport paths from the dayside and from the nightside to space. Moreover, the response of escaping plasma structures to changing solar wind conditions will shed light on the dynamic evolution of the system. Mapping the paths of escaping plasma structures will result in a better understanding of the evolution of atmospheric escape at Mars and the contribution of escaping plasma structures to the total atmospheric loss. In this study we probe escaping plasma structures utilising two special campaigns of ESA's Mars Express mission as well as observations from NASA's MAVEN mission, in the high-altitude nightside ionosphere of Mars. Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) is the radar on board Mars Express and samples the ionosphere at altitudes no higher than ~1500 km. However, in our study we look at observations from consecutive orbits during two special MARSIS campaigns, each consisting of 5 orbits, that took place in September 2023 and April 2024, for which MARSIS was operated at altitudes up to ~5000 km.
We see a variable nightside ionosphere at high altitudes that changes between consecutive MEX orbits. MARSIS detects plasma structures appearing at different altitudes or disappearing between orbits. We compare with MAVEN measurements to better evaluate both the escaping plasma structures and the solar wind conditions. MAVEN too sees plasma structures at high altitudes on the nightside, changing between orbits, confirming the variability of the high-altitude nightside ionosphere and revealing a dusk-dawn asymmetry in the observed electron densities.
How to cite: Stergiopoulou, K., Lester, M., Joyce, S., Andrews, D., Edberg, N., Persson, M., Xu, S., Romanelli, N., Curry, S., Holmström, M., Fowler, C., Ma, Y., Ramstad, R., Kim, K., Sánchez-Cano, B., Aizawa, S., and Cicchetti, A.: Escaping plasma structures in the Martian magnetotail as observed during two special MARSIS high-altitude campaigns, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-1420, https://doi.org/10.5194/epsc-dps2025-1420, 2025.
