The high latitude ionospheric convection pattern during northward interplanetary magnetic field

n investigation of the earth's magnetospheric convection signature in the high latitude ionosphere is conducted using spacecraft observations. In particular we examine the ionospheric convection pattern under various interplanetary magnetic field conditions. The DMSP F8 satellite's coverage of the earth's polar regions provides horizontal ion drift velocities along the dawn-dusk meridian at about 835 km altitude in each hemisphere during the approximately 100 minute orbital period. We first consider five passes over the southern summer hemisphere during a time when the z component of the interplanetary magnetic field was stable and positive and the y component changed slowly from positive to negative. Large-scale regions of sunward flow are observed at very high latitudes consistent with a strong z component. When ;We next examine the ionospheric convection signatures observed by DMSP F8 in the summer and winter hemispheres during periods when the IMF is directed northward for at least 45 minutes prior to the satellite entering the polar region and remains northward throughout the polar pass. These convection signatures can be readily categorized by the number of sunward and antisunward flow regions and by their potential distributions. Here we describe the most frequently identifiable and reproducible features of the convection pattern that exist during steady northward IMF conditions. In addition to IMF...