Solar Wind—Ionosphere Interface at Mars. Ion Dynamics, Asymmetry, Plasma Jets

Abstract

We report on observations made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, in the shocked solar wind-ionosphere interface of Mars. We observe a strong asymmetry in plasma flow governed by the direction of the motional electric field. In the hemisphere, in which the motional electric field ∼−V × B is pointed outward the planet the solar wind flow is decelerated by the j × B force related to the magnetic field compression in the barrier. In contrast, in the opposite hemisphere, the solar wind flow is accelerated. The gain in velocity is about 100–200 km/s. The dynamics of ionospheric ions are also very different on both sides. Such an asymmetry implies very different patterns of the electric current closure and the electromagnetic forces in both hemispheres.