A linear analysis is carried out to investigate how the return current is generated for the field-aligned current carried by a super-Alfv¿nic auroral electron beam. If the electron beam is a thin sheet with thickness less than or equal to the electron inertia length (L≲c/&ohgr;pe), the negative space charge of the beam is neutralized by the ion polarization current produced by the beam. The return current in this case is generated on the two outsides of the beam connected to the polarization current to form a closed current loop. This current structure can explain the thin (a few kilometers) current sheets in the auroral arcs observed by satellites. The current in the thin electron beam propagates at the beam speed which is super-Alfv¿nic. If the beam width is much greater than the electron inertia length, the polarization current is not enough to neutralize the negative space charge of the super-Alfvenic beam, so that the beam current must be neutralized by the background electrons. ¿ American Geophysical Union 1989