First start-to-end global imaging of a sunward propagating giant undulation event: IMAGE/FUV observations

During intervals of very high convection, large-scale ``giant undulations" are sometimes observed to develop on the duskside equatorward edge of the diffuse aurora and are thought to be due to the onset of a velocity shear instability at the plasma sheet-plasmasphere interface. Although these features were first identified in space-based auroral imager data (DMSP in the early 1980's), their dynamics have been explored almost exclusively with ground-based all-sky camera data (and consequently over only a limited spatial extent). Several high time resolution frames from the Freja imager have been reported previously, but the images were acquired over a very small time window and no motion of the undulations was detected. Here, we present the first ever high-time resolution global imaging of a sunward propagating giant undulation event from start to finish. The event occurred on November 24, 2001 during a very disturbed storm interval. The giant undulations began to develop at around 13UT and persisted for approximately 2 hours. The sunward propagation speed was on the order of 0.6 km/s. In addition to the IMAGE/FUV observations (WIC, SI-12, and SI-13 passbands), numerous other datasets will be presented including ground magnetometer data which show that the undulations were associated with Pc5 type magnetic pulsations. Geosynchronous particle data and other IMAGE datsets will also be presented. Possible generation mechanisms for the giant undulations will be discussed.