Storm time signatures of the zonal ion drift and region-2 field-aligned current at middle latitude ionosphere

Many studies have now shown that magnetospheric influences can be identified in the electrodynamic signatures of the ionosphere at low and middle latitudes. Magnetospheric influences are observed in terms of the equatorward extent of the ion convection and the auroral particle precipitation. Using a quantitative identification of convection, particle precipitation and region-2 field-aligned current boundaries of the DMSP F13 data set at high latitudes, the relative extent of auroral convection and precipitation is examined. This limited study shows during the main phase of the superstorm ion drifts driven by the magnetosphere penetrate to the dip equator on the dusk side, whereas the equatorward extent of the region-2 field-aligned current signatures extends to as low as 39 degrees MLAT. This magnetic perturbation may be indicative of a distributed field-aligned current within the plasmasphere that is set up to to insure the same ExB drift motion of the plasma in both hemispheres. Another feature, which is seen later in the storm phase, is the presence of the magnetic perturbation over a smaller scale indicating the presence of an upward field-aligned current equatorward of the region-2 current system.