Comparison of Auroral Electrojets and the Visible Aurora

Abstract

Examination is made of latitude profiles of visible auroral emissions at 3914 Å and 5577 Å and latitude profiles of magnetic perturbations at times of several passes of the ISIS 2 satellite over the evening sector auroral oval. In agreement with recent studies, it is found that the basic conductivity channel of the polar electrojet is provided by diffuse auroral precipitation, but this channel can be modified by discrete auroral precipitation (arcs or arc systems). Some magnetic latitude profiles have been inverted to obtain meridional profiles of the electrojet current density distribution. These current profiles are characterized by a broad zone of current with superimposed narrower regions of more intense current. The narrow intense currents frequently occur underneath discrete arcs. But not all discrete arcs are associated with current density increases. Arcs at or near the Harang discontinuity and some arcs poleward of the electrojet possess small current densities relative to within the electrojet. A reversal of the ionospheric electric field direction within these arcs is believed to be responsible.