Model investigation of the influence of the crustal magnetic fieldon the oxygen ion distribution in the near Martian tail

摘要

To investigate the influence of the Martian crustal magnetic field on the accelerationand escape of the planetary ions in the near tail region, the distributions of planetary oxygenions are studied by means of test particle simulation in an electromagnetic environmentcreated by a recent multispecies Magnetohydrodynamics (MHD) simulation of the solar windinteraction with Mars, with crustal field included or excluded. Results under differentcrustal field conditions are compared to determine the effects of crustal field. It is found thatwhen crustal field is present, draped magnetic field lines are replaced by closed field linesin the near tail region and the electric field is also intensified because of the Hall effect. As aresult, the oxygen ion distribution reveals distinct stream structures in the tail region whencrustal field is included, with one hot stream at the central tail and two cold streams at the flankof the tail. Some energetic ions inside the hot stream are accelerated toward the planet,instead of escaping downstream.