Field‐Aligned Potentials at Mars From MAVEN Observations

Abstract

AbstractOne possible ion escape channel at Mars is a polar wind‐like outflow driven by parallel electric fields and/or other acceleration mechanisms. With independent potential estimates from ionospheric photoelectron measurements by the Solar Wind Electron Analyzer (SWEA) and ion measurements by the SupraThermal And Thermal Ion Composition (STATIC) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, magnetic field‐aligned potentials are calculated as the difference of the two. The calculated field‐aligned potentials have average values that range from 0 to −1.5 V, relative to the ionospheric source region. These field‐aligned potentials likely result from ambipolar electric fields and are found on both closed and open field lines. On the dayside, these potentials range from 0 to −0.7 V, corresponding to an electric field magnitude <3 mV/km, which peaks near the ion exobase and can effectively accelerate ions and enhance ion outflow.