Global Ambipolar Potentials and Electric Fields at Mars Inferred From MAVEN Observations

Shaosui Xu , David L. Mitchell , Yingjuan Ma , Tristan Weber , David A. Brain , Jasper Halekas , Suranga Ruhunusiri , Gina Dibraccio , Christian Mazelle (1)

1 IRAP - Institut de recherche en astrophysique et planétologie

The motion of charged particles is governed by electromagnetic forces at high altitudes at Mars and thus the characterization of electrostatic potential and electric fields is important for understanding ion escape at Mars. In this study, we utilize measurements from the Mars Atmosphere and Volatile EvolutioN mission to derive electrostatic potentials above the collisional atmosphere at Mars. We find averaged potentials to be up to ∼100 V in the magnetosheath and down to ∼-70 V in the tail, with respect to the upstream. We then derive electric fields based on averaged potential maps, ranging ∼0.01-0.1 V/km. These data-derived electric fields are in good agreement with ambipolar electric fields from a multi-fluid magnetohydrodynamic (MHD) model. MHD results also reveal that these large electric fields mainly originate from the electron pressure gradient in the magnetosheath and in the transition region from the hot solar wind flow to the cold ionospheric flow. This work provides the first data-based characterization of global ambipolar electric fields at Mars (outside of the main ionosphere).

Mots clés: ambipolar electric field; ion escape; Sun-Mars interaction; particle acceleration; solar wind electrons; MAVEN

Domaines: Planète et Univers [physics]

Shaosui Xu, David L. Mitchell, Yingjuan Ma, Tristan Weber, David A. Brain, et al.. Global Ambipolar Potentials and Electric Fields at Mars Inferred From MAVEN Observations. Journal of Geophysical Research Space Physics, 2021, 126, ⟨10.1029/2021JA029764⟩. ⟨insu-03672337⟩