A MODELING STUDY OF ANISOTROPIC ION TEMPERATURES GENERATED IN THE F-LAYER BY SUBAURORAL ION DRIFTS

A model of the ionosphere and plasmasphere, used previously to study t he effects of subauroral ion drifts (SAID), has been enhanced to take account of O+ temperature anisotropy relative to the geomagnetic field direction. The ion-neutral frictional heating due to the SAID is part itioned preferentially into the O+ perpendicular distribution, leading to the perpendicular distribution temperature, T-perpendicular to, ex ceeding the parallel distribution temperature, T-parallel to, in the F -region and topside ionosphere. The model results for SAID velocities of 1-4 hm s(-1), for solar maximum and solar minimum conditions, are c onsistent with SAID data from satellite observations and with T-perpen dicular to/T-parallel to values measured by EISCAT.