INTERHEMISPHERIC CONTRASTS IN THE IONOSPHERIC CONVECTION RESPONSE TO CHANGES IN THE INTERPLANETARY MAGNETIC-FIELD AND SUBSTORM ACTIVITY - ACASE-STUDY

Interhemispheric contrasts in the ionospheric convection response to v ariations of the interplanetary magnetic field (IMF) and substorm acti vity are examined, for an interval observed by the Polar Anglo-America n Conjugate Experiment (PACE) radar system between similar to 1600 and similar to 2100 MLT on 4 March 1992. Representations of the ionospher ic convection pattern associated with different orientations and magni tudes of the IMF and nightside driven enhancemecnts of the auroral ele ctrojet are employed to illustrate a possible explanation for the cont rast in convection flow response observed in radar data at nominally c onjugate points. Ion drift measurements from the Defence Meteorologica l Satellite Program (DMSP) confirm these ionospheric convection flows to be representative for the prevailing IMF orientation and magnitude. The location of the fields of view of the PACE radars with respect to these patterns suggest that the radar backscatter observed in each he misphere is critically influenced by the position of the ionospheric c onvection reversal boundary (CRB) within the radar field of view and t he influence it has on the generation of the irregularities required a s scattering targets by high-frequency coherent radar systems. The pos ition of the CRB in each hemisphere is strongly controlled by the rela tive magnitudes of the IMF B-z and B-y components, and hence so is the interhemispheric contrast in the radar observations.