Structure and dynamics of polar patches above Casey, Antarctica. Original Research Article

A Lowell Digital Ionosonde (DPS-4) has been used at the Australian Antarctic polar cap station Casey (−80.6° CGM latitude) in a study of ionospheric polar cap patches. The instrument ran a series of campaigns consisting of 3-minute cycles of ionograms and drift velocity measurements during 1997–1999. Patches identified from group range and critical frequencies on the ionogram records were compared with drift measurements and other geophysical data sets. Correlations were observed with Total Electron Content derived from GPS satellite observations with a receiver also located at Casey. Comparisons with plasma drift velocities, (derived from DPS drift measurements), indicate that patches are often associated with apparent fluctuations in horizontal drift velocity. Peaks in the horizontal velocity appear to correlate with the patch edges. Possible explanations of these observations are discussed. This paper considers case studies of patch observations in April 1998.