Electric Mars: A large trans-terminator electric potential drop on closed magnetic field lines above Utopia Planitia

Glyn Collinson , David Mitchell , Shaosui Xu , Alex Glocer , Joseph Grebowsky , Takuya Hara , Robert Lillis , Jared Espley , Christian Mazelle (1, 2) , Jean-André Sauvaud (1, 2) , Andrey Fedorov (1, 2) , Mike Liemohn , Laila Andersson , Bruce Jakosky

1 IRAP - Institut de recherche en astrophysique et planétologie
2 UT - Université de Toulouse

Parallel electric fields and their associated electric potential structures play a crucial role in ionospheric-magnetospheric interactions at any planet. Although there is abundant evidence that parallel electric fields play key roles in Martian ionospheric outflow and auroral electron acceleration, the fields themselves are challenging to directly measure due to their relatively weak nature. Using measurements by the Solar Wind Electron Analyzer instrument aboard the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) Mars Scout, we present the discovery and measurement of a substantial (Φ_Mars=7.7 ± 0.6 V) parallel electric potential drop on closed magnetic field lines spanning the terminator from day to night above the great impact basin of Utopia Planitia, a region largely free of crustal magnetic fields. A survey of the previous 26 orbits passing over a range of longitudes revealed similar signatures on seven orbits, with a mean potential drop (Φ_Mars) of 10.9 ± 0.8 V, suggestive that although trans-terminator electric fields of comparable strength are not ubiquitous, they may be common, at least at these northerly latitudes.

Mots clés: Mars; electric fields; polarization electric field; MAVEN

Domaines: Planète et Univers [physics]

Glyn Collinson, David Mitchell, Shaosui Xu, Alex Glocer, Joseph Grebowsky, et al.. Electric Mars: A large trans-terminator electric potential drop on closed magnetic field lines above Utopia Planitia. Journal of Geophysical Research Space Physics, 2017, 122, pp.2260-2271. ⟨10.1002/2016JA023589⟩. ⟨insu-03677077⟩