Duskside auroral undulations observed by IMAGE and their possible association with large‐scale structures on the inner edge of the electron plasma sheet

On February 6, 2002 large‐scale undulations along the equatorward edge of the afternoon/dusk auroral oval were observed with the IMAGE FUV/Wideband Imaging Camera (WIC) during the late expansion/recovery phase of a substorm. The undulations are similar to others previously reported, but occur at higher than usual latitudes and map to the outer duskside magnetosphere, 1 to 2 RE beyond a plasmaspheric drainage plume. The mapping suggests that the undulations result from large‐scale fluctuations on the inner edge of the electron plasma sheet. 2.5‐D simulations using representative plasma parameters for this region indicate that such large‐scale coherent structures can be created by a kinetic drift wave driven by the ion pressure gradient in the destabilizing curvature and grad B drift of the plasma sheet ions.