A model of the auroral electrojets

Certain observations indicate that the auroral electrojets are confined to the auroral arcs. A model of an arc is presented in which the height variation of the auroral ionization is taken into account and vertical currents are allowed to flow. The current flow in the arc is investigated, and the electric field or wind velocity field required to drive the currents is computed for two different cases: in one, the current flow between the auroral-zone ionosphere and the outer magnetosphere is assumed to be limited and electric fields occur along the magnetic field lines in the magnetosphere; in the other, the conductivity along the field lines is assumed to be perfect. In the first case the electrojets are probably driven by a longitudinal electric field in the magnetosphere. In the second case the driving electric field must be a meridional field in order to explain the observations, and strong sheet currents must flow along the field lines that connect the auroral ionosphere to the outer magnetosphere.