Solar-wind dependencies of high-latitude convection and precipitation

The solar-wind plasma and interplanetary magnetic field (IMF) dependencies of the patterns of plasma convection and particle precipitation in the high-latitude ionosphere were investigated by constructing average patterns of the ionospheric electric field and the precipitating energy influx of different solar-wind conditions. A data base of over 100 days' observations of high-latitude plasma convection with the Millstone Hill radars was sorted and binned according to the one-hour averaged values of MF Bz and Bv. The individual line of sight velocities observed by the radar were combined in each magnetic latitude-local time bin to derive statistically averaged convection patterns between 50 and 73 degrees latitude. A 25-mV/m southward electric field is found at auroral latitudes in the midnight sector for IMF away sectors (By>O) while a southward-directed IMF increases the cross polar-cap potential difference from 15 kV (for Bz>+3 nT) to 75 kV (for Bz<-3 nT). For geomagnetically disturbed conditions (Kp=-to 5-), the additional requirement that Bz be negative results in a 30-kV potential difference across an enhanced dayside region of plasma entry into the polar cap.