On the horizontal currents over the Martian magnetic cusp

Localized crustal magnetization over heavily cratered southern hemisphere at Mars gives rise to open magnetic field configurations which interact with the solar wind magnetic field to form magnetic cusps.  The downward acceleration of energetic electrons in these cusps can produce aurora and an extended topside ionospheric structure over regions of magnetic anomalies.  We report plasma collisions with the neutral atmosphere at one of the Martian cusps located at 82^oS and 108^oE, where the crustal field is strong with a radial component ~30^o from the local zenith.  We find that the dynamo region in the upper ionosphere of Mars is located between altitudes of 102 km and 210 km. The electrons in this region are constrained to gyrate along magnetic field lines while ions are dragged by neutrals and move along the direction of applied force.  In the absence of the electric field, the horizontal current in the Martian dynamo is generated by the differential motion of ions and electrons.  We find that the bulk of the current density is equatorward and confined within the Martian dynamo near the ionospheric peak with a magnitude of ~3.5 µA/m².  We also find that the westward current density of magnitude ~0.4 µA/m² peaking near the upper boundary of the Martian dynamo is generated by magnetized ions in the -F x B direction.  The model details and results in comparison with other studies will be presented.