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

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 similar to-V x B is pointed outward the planet the solar wind flow is decelerated by the j x 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. Solar wind interacts directly with the ionosphere of Mars. The flow pattern in the interface region of such an interaction turns out to be different for different orientations of the interplanetary magnetic field. This asymmetry is governed by the direction of the motional electric field -1/c(V x B) aroused due to the solar wind flow across the magnetic field. Structure of the interface occurs very different. In the hemisphere, in which the motional electric field is pointed outward of Mars, the shocked solar wind flow is decelerated. In the hemisphere, in which the motional electric field is pointed toward the planet, the plasma flow is accelerated. Plasma flow in the solar wind-ionosphere interface at Mars depends on sign of the cross-flow component of the interplanetary magnetic field The motional electric field in the solar wind controls such a flow in the interface The shocked solar wind is accelerated in the interface of the hemisphere in which the motional electric field pointed toward the planet