Electric fields and currents were studied at the night side of the auroral oval. The electric field distribution between the field-aligned current sheets is determined by the Pedersen conductivity of the ionosphere. The ionosphere is a load in an electric circuit whose generator is located in the magnetosphere. The site of electric field generation is assumed to be the current sheet of the magnetospheric tail. The plasma in the tail is assumed to be polarized under the influence of a Lorentz force. The polarization field is projected along geomagnetic field lines to the auroral zone and causes the Hall current that constitutes a westward electrojet. ¿ American Geophysical Union 1988