The shift of the auroral electron precipitation boundaries in the dawn‐dusk sector in association with geomagnetic activity and interplanetary magnetic field

Abstract

On the basis of the auroral precipitating electron data along the dawn‐dusk meridian from a Defense Meteorological Satellite Program satellite (DMSP‐F2), we show that the electron precipitation region extends poleward, often to the geomagnetic latitudes ≳85° from the average oval location, during quiet periods (namely, during periods of a large positive B z component). This result may be interpreted as an indication that only a small amount of geomagnetic flux interconnects with the northward IMF, resulting in a contracted “open” region (the polar cap). The control of the location of the poleward boundary by the north–south component of the IMF is also statistically examined. The rate of latitudinal movement is about 0.4° to 0.8° per 1 nT for positive IMF B z values and about 0.7° to 1.1° per 1 nT for negative IMF B z values. The shift of the equatorward boundary is not obvious, however, for positive IMF B z values. As geomagnetic activity increases, both the poleward and equatorward boundaries shift toward lower latitudes. The equatorward shift of the poleward boundary is greater than that of the equatorward boundary, resulting in a thinner electron precipitation region during disturbed periods than during quiet periods.