Summary
A Lowell Digital Ionosonde (DPS-4) has operated at the Australian Antarctic polar cap station Casey (-80.6o CGM latitude), since early 1993, primarily to study the dynamics of the southern polar cap ionosphere. To gain a better understanding of the ionospheric motions involved, animated data displays have been developed using ionospheric drift and ionogram data combined together with other geophysical data sets to help identify dynamical features. These displays generally show ionospheric skymaps (echo locations), drift velocities and Doppler ionograms (vertical profiles), produced with a resolution of up to a frame every 2 minutes. Ionospheric changes can then be viewed frame by frame using commercial animation software. This provides a simple means of viewing large amounts of data and identifying, for example, drifting polar patches, or the response of ionospheric drift to changes in the IMF. Since the ionosonde takes measurements throughout the bottomside ionosphere, different height regions (eg. E and F) can be examined independently or compared directly. Doppler and directional information featured in the animations provide a powerful technique for studying the evolution of ionospheric phenomena, such as polar patches. This paper will demonstrate the applications of the ionomovie animations, and then concentrate on a specific research project using the digisonde for a study of polar patches. Several campaigns were undertaken with the DPS-4 during 1997 and early 1998 with the aim of identifying the occurrence and motion of polar patches over Casey. Polar patches identified from ionosonde records were compared with other geophysical data sets. Initial results show good correlations between group range and critical frequency ionosonde measurements, and Total Electron Content derived from GPS observations. The field-of-view for GPS observations allows patches to be observed over large distances, providing some insight into their origin. The influence of the