Summary
During 1997 and early 1998 a series of campaigns were undertaken at the Australian Antarctic polar cap station Casey (-80.6o CGM latitude) with the aim of identifying and gaining further understanding of polar patches. The main instrument used for these campaigns was a Lowell Digital Ionosonde (DPS-4) [1], running a 3 minute cycle of ionograms and drift velocity measurements. Patches identified from group range and critical frequencies on the ionogram records were compared with drift measurements and other geophysical data sets. Good correlations were observed with Total Electron Content derived from GPS satellite observations with a receiver also located at Casey. The field-of-view for GPS observations allowed patches to be observed over large distances, providing some insight into their origin. The influence of the Interplanetary Magnetic Field on the formation and occurrence of patches was also investigated. Comparison with plasma drift velocities, (derived from DPS drift measurements), indicated that patches are associated with fluctuations in horizontal drift velocity as observed by other researchers [2]. In the current study, peaks in the horizontal velocity correlate with the patch edges. Further investigations of polar patches will involve comparison with GPS scintillation measurements, SuperDARN radar observations, conjugate studies and satellite images (eg. POLAR).