Plasma injection and transport in the mid-altitude polar cusp

DE-1 hot plasma observations in the mid-altitude polar cusp have shown evidence of a significant velocity filtering phenomenon which is consistent with a latitudinally narrow region of plasma injection located at a geocentric distance of about 8 R/sub E/ (in a dipole approximation). Plasma convection from the injection region into the polar cap results in a 'V'-shaped log E vs. α0 relation at geocentric distances near 4 R/sub E/. This velocity filtering effect allows the measurement of much smaller flow velocities (approx.10 km/s) than have heretofore been possible with hot plasma measurements. The flows thus determined are consistent with ionospheric flows measured nearly simultaneously by the DE-2 spacecraft, although the magnitudes of the higher altitude flows are higher by a factor of 2 or more than an approx.r/sup 3/2/ dipole-field mapping would predict