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Altitude dependence of nightside Martian suprathermal electron depletions as revealed by MAVEN observations


Steckiewicz Morgane




Auteur(s) supplémentaire(s)C. Mazelle, P. Garnier, N. Andre, E. Penou, A. Beth, J.-A. Sauvaud, D. Mitchell, J. McFadden, J. Luhmann, J. Connerney, L. Andersson, B. Jakosky
Institution(s) supplémentaire(s)Université de Toulouse, UPS-OMP (France); Space Science Laboratory, Berkeley (USA); NASA Goddard Space Flight Center, Greenbelt (USA); Laboratory for Atmospheric and Space Physics, Boulder (USA)


The MAVEN (Mars Atmosphere and Volatile  evolution) spacecraft is providing new detailed observations of the Martian ionosphere thanks to its unique orbital coverage and instrument suite. During most periapsis passages on the nightside ionosphere suprathermal electron depletions were detected. A simple criterion was implemented to identify the 3707 depletions observed from November 2014 to February 2015 above the Northern hemisphere and from June to September 2015 above the Southern hemisphere. A statistical analysis reveals that the main ion and elec-tron populations within the depletions are surprisingly constant in time and altitude. Absorption by CO2 is the main loss process for suprather-mal electrons, and electrons that strongly peaked around 6 eV are resulting from this interaction. The observation of depletions appears however highly dependent on altitude. Depletions are mainly located above strong crustal magnetic sources above 170 km, whereas the depletions observed for the first time below 170 km are globally scattered onto the Martian surface with no particular dependence on crustal fields.

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