A model‐derived storm time asymmetric ring current driven electric field description

Abstract

Low‐latitude ionospheric and near‐Earth magnetospheric electric fields are calculated from model results of the storm time asymmetric ring current. These fields are generated from subauroral field‐aligned currents out of the ionosphere in the midnight sector and into the ionosphere on the dayside. The currents balance the divergence of the asymmetric ring current, which is the dominant component of the ring current during main phase and early recovery phase of magnetic storms. The basic shape of the electric potential pattern is described, both in the ionosphere and in the magnetosphere. It is found that intense ring current injection events can create potential differences up to 200 kV and can create local electric fields in the nightside magnetosphere >5 mV m−1. The magnitudes and locations of the most intense electric fields are quite consistent with observations of subauroral (ionospheric) and near‐Earth (magnetospheric) electric fields during magnetic storms. In addition, a relationship between the magnitude of the low‐latitude electric potential and theDst* index is described. This relationship can be used to predict the location and size of strong low‐latitude electric fields and currents. The presented electric field results are derived from model output, such that there is no feedback of the calculated fields back into the model.