Net field-aligned currents controlled by the polar ionospheric conductivity

Abstract

The results of an analysis of the east-west magnetic variations at midlatitudes suggest that the net field-aligned currents, which are the integral of the downward and upward field-aligned currents along a meridian, are strongly controlled by the polar ionospheric conductivity. The east-west magnetic disturbances at midlatitudes are expected to be the magnetic effects of the net field-aligned currents in the polar region. We have examined the relation between the auroral electrojet intensity represented by the auroral electrojet (AE) index and the net field-aligned current intensity represented by the east-west magnetic disturbances at midlatitudes. It is deduced from this analysis that the net field-aligned currents are upward on the nightside and downward on the dayside. It is also derived that the net upward field-aligned currents on the nightside are stronger in winter than in summer. This seasonal dependence can be explained by the seasonal variation of the polar cap ionospheric conductivity. Copyright 2002 by the American Geophysical Union.