Auroral Undulations in the Afternoon/Dusk Sector Observed with the IMAGE
FUV/Wideband Imaging Camera  and Their Magnetic Connection to Plasmaspheric
Plumes

W.S. Lewis, J.L. Burch, J. Goldstein, S.B. Mende, H.U. Frey, T.J. Immel, 
M.F. Thomsen, and B.R. Sandel


On February 6, 2002 the IMAGE FUV/Wideband Imaging Camera (WIC) detected a
periodic series of tongue-like emission features that extended equatorward from
the main auroral oval in the afternoon/dusk sector. Although clearly discernible
in the electron aurora, these features cannot be distinguished from background
in simultaneous images of the proton aurora. The emission tongues were observed
during the recovery phase of a moderate magnetic storm and occurred during a
substorm expansion phase. Their wavelength, amplitude, and westward velocity are
consistent with those reported for giant undulations observed at the equatorward
edge of the diffuse aurora. However, the features seen on February 6 are
embedded within a broader band of diffuse auroral emissions and in two instances
are observed to brighten in conjunction with brief, localized intensifications
along the portion of the oval to which they are connected. The emission tongues
map to a well-developed plasmaspheric drainage plume, seen in geosynchronous
plasma data as well as in near-simultaneous data from the IMAGE Extreme
Ultraviolet (EUV) imager. We discuss this event in the context of previous work
on undulations at the equatorward edge of the  aurora and consider its
implications for the various mechanisms that have been proposed to account for
such structures.

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Presentation, Fall A.G.U. Meeting, San Francisco, CA, 13-17 December 2004