Plasma convection in the Earth's magnetosphere and ionosphere during substorms

The empirical field-aligned current (FAC) and plasma convection model on which this paper is based describes the four phases of a typical substorm. 2D maps of the ionospheric electric potential (U) are shown here for the first time for each of these phases. The principal result is the identification of medium-scale ionospheric convection vortices, which are observed in addition to the well-known two large-scale DP2 convection cells. We conclude that these convection vortices are the analogue to the heterogeneities that were found earlier in the spatial distribution of the FAC density. They had been taken into account there in the framework of the conceptual model of magnetospheric generators. This model is extended in the present paper such that it also describes the above-mentioned medium-scale convection vortices.