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

M.G. Henderson, E.F. Donovan, S.B. Mende, T.J. Immel, and M.F. Thomsen


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.

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Fall 2002 Meeting of the American Geophysical Union
San Francisco, CA, USA, 6-10 December 2002