Understanding the field aligned current (FAC) system in substorms is one of the central themes of magnetospheric physics. Three-dimensional (3D) magnetohydrodynamic (MHD) simulations of magnetotail reconnection has shown that FAC structures similar to the wedge-current system are indeed reproduced either with or without a dipolar region situated at the earthward end of a current sheet. In this study, however, by noting that the ion inertia length is not negligibly small compared to the current sheet width in the magnetotail, we investigate the FAC generation mechanism in the Hall-MHD system. For an idealized current sheet geometry without the dipolar region, we find that the results obtained to be totally different from the MHD results.
