Hall-MHD modeling of near-Earth magnetotail current sheet thinning and evolution

The formation of thin current sheets is a common feature of the late substo rm growth phase in the magnetotail of the Earth. The location and the struc ture of the evolving thin current sheet determine the onset and the dynamic phase of magnetic substorms. To determine the formation and further evolut ion of thin current sheets in the near-Earth magnetotail, we employ a two-f luid model of electrons and ions, the Hall-MHD. We start from a two-dimensi onal tail-equilibrium model and apply a plasma inflow from the lobes to sim ulate the presubstorm loading process of the tail. Our results confirm rece nt 2.5-dimensional particle and hybrid simulations which have shown thin cu rrent sheet formation, with the majority of the new current supported by th e electrons. The Hall-MHD simulations are extended to a current sheet thinn ing model with three-dimensional driving: conditions and different magnetic field boundary conditions. We investigated the changes to the tail magneti c and current structure brought about by the cross-tail magnetic field comp onents generated by Hall electric fields. For all these cases, the addition al current is carried by the electrons, with very small effects of magnetic field and driving boundary conditions.