IONOSPHERIC PLASMA CONVECTION IN THE SOUTHERN-HEMISPHERE

The first ionospheric plasma convection maps ordered by the y- and z-c omponents of the IMF using only data from the southern hemisphere are presented. These patterns are determined from line-of-sight velocity m easurements of the Polar Angle-American Conjugate Experiment (PACE) lo cated at Halley, Antarctica, with the majority of the observations com ing from 65 degrees-75 degrees magnetic latitude. For IMF Bz positive and negative conditions, the observed plasma motions are consistent wi th a standard two cell pattern. For the periods from dusk through midn ight to dawn, flow speeds are at least twice as large for Bz negative component compared with Bz positive. The observations about noon are s ignificantly different from each other. For Bz positive, little ordere d plasma motion is observed. For Bz negative, there are large anti-sun ward hows the orientation of which is ordered by IMF By. These By orie ntated flows are consistent with theoretical predictions, and are anti -symmetric to those reported from the northern hemisphere. The two mos t significant differences from previous observations are that the conv ection reversal in the late morning sector for By negative conditions occurs at about a 4 degrees lower latitude than the Heppner and Maynar d (1987) model. This may be due to a seasonal bias in the PACE dataset . Also, the separatrix between eastward and westward flow near midnigh t has a very different shape dependent upon the orientation of IMF By. For positive By conditions, the separatrix is observed at progressive ly lower latitudes at later local times, but for By negative condition s, the separatrix appears at increasingly higher latitudes at later ti mes.