Ionospheric Currents at Mars Over the Region of Crustal Magnetic Anomaly

Many magnetic cusps have been identified on Mars while interpreting the crustal magnetic field and electron density data. One of such cusps is located at 82^oS and 180^oE where the crustal magnetic field is nearly vertical and open to the access of solar wind plasma through magnetic reconnection. This reconnection can modify the topside Martian ionospheric structure by downward accelerating electrons and upward accelerating ions. We use our 1-D chemical diffusive model to interpret the measured electron density profile at 82^oS and 180^oE with the vertical plasma transport simulated by vertical ion drifts. The output of this model and available crustal magnetic field information at Mars are used to estimate the vertical distribution of the ionospheric conductivity. We find that the ionosphere is highly conductive in the Martian dynamo region between 100 and 210 km altitude where plasma -neutral collisions permit electric currents when an external force is applied to the plasma. This force drags the collisional ions along with it while the drifting electrons move in a direction perpendicular to both the applied force and the crustal magnetic field. This differential motion of ions and electrons derives electric currents in the Martian ionosphere. According to Fillingim et al. [2010], strong currents are generated at magnetic cusps near the ionospheric peak for a given magnitude of a uniform neutral wind. We use their methodology and calculate the zonal and meridional components of ion and electron velocities with assumptions that the magnetic field is vertical and a constant neutral wind is set to 100 m/s northward. We find that the meridional current pointing northward is primarily driven by the collisional ions with a peak value of 1 μAmpere/m² near the Martian ionospheric peak. The zonal current is more extended in altitude, peaking near the upper boundary of the dynamo region ( 200 km altitude) with a magnitude -1.5 μAmpere/m² (westward). The model results will be presented in comparison with existing estimates of the Martian conductivity and ionospheric currents. This work is supported by Mohammed Bin Rashid Space Center (MBRSC), Dubai, UAE, under Grant ID number 201604.MA.AUS.