The Mars Space Current System Distribution Characteristics

Based on the multi-species, single fluid MHD model, this paper calculates and analyzes respectively the distribution of the currents in the Martian space, with the influence of the currents due to the crustal magnetic fields. The results show there are 4 categories of currents, the bow-shock current, magnetic pileup boundary current, the ionosphere current and the magnetotail current in the Martian space. The local crustal magnetic fields have different influence on the distribution of the four currents. The characteristics of global distribution of the Martian currents are as follows.Currents flow on the surface of the bow-shock independently,which direction perpendicular to the interplanetary magnetic field direction, with the peak current density located around the sub-solar point. At dayside, the magnetic pileup boundary current closes through the ionosphere; while at night-side, magnetic pileup boundary current couples with central current sheet in the magnetotail to form a complete circuit. Magnetotail central currents near Mars within 1.3 RM affected greatly by the ionosphere, would be separated for two or more current slices coupling together. The strength of ionosphere current is the biggest in all , more than 100nA/m2 in average;and the strength at dayside is bigger compared to that of the nightside.The crustal magnetic fields change the features of the distribution of the four currents in some aspects. The curvature of bow shock current sheet with the presence of the crustal magnetic fields is larger than that excluding crustal magnetic fields, with the average position of the bow-shock further away from Mars. At dayside of Mars, the existence of crustal magnetic fields made magnetic pileup boundary current density larger than that without the crustal magnetic fields; while locations of where the magnetic pileup boundary currents flow in and out at south and north have some angle with respect to the XZ plane (MSO coordinates) at nightside, with larger current radius than that not have crustal magnetic fields too. At nightside, near the planet, several current slices coupling together, but the crustal magnetic fields have limited influence on the distribution of magnetotail current, just only within 1.8RM from Mars. With the crustal magnetic fields, the distribution of ionosphere current is quite complex , and some southern hemisphere current strength could reach more than 10 000 nA/m2,but not changing the different characteristics of current distribution at dayside and nightside as a whole. On the other hand, the crustal magnetic fields do not change the general trend of ionosphere current direction, flowing from south to north. However they make part of regional currents mixed and disordered extreamly, with looped, wrinkled current streamlines in some parts of the southern ionosphere.