An Overview of IMAGE EUV Observations of the Plasmasphere B. R. Sandel, R. A. King, W. T. Forrester, D. L. Gallagher, C. C. Curtis, A. L. Broadfoot The Extreme Ultraviolet Imager (EUV) of the IMAGE Mission records the spatial distribution of He+ in the plasmasphere with a time resolution of 10 minutes and a spatial resolution of 0.1 RE or better. EUV measures the brightness of 30.4-nm sunlight resonantly scattered by He+ surrounding Earth. The 30.4-nm emission from the plasmasphere is optically thin, so the measured brightness in each resolution element is directly proportional to the He+ number density integrated along the corresponding line of sight through the plasmasphere. The individual image frames, and especially movies made from them, reveal a host of distinct plasmaspheric features and behaviors. Many of these had already been inferred during the more than three decades of investigations of the plasmasphere using ground-based and in situ techniques, but some of them appear to be new. And global imaging offers new perspectives on even the previously-known features. Among the features accessible to study using EUV are: 1) Plasma tails, which connect to the main plasmasphere in the dusk sector and extend sunward. Their typical length is 3--4 RE, and they are separated from the main plasmasphere by a density trough in which brightnesses are reduced by a factor of roughly 6. The most spectacular example of this phenomenon recorded to date had a width of about 1 RE. 2) Regions of plasma detached from the main plasmasphere. 3) Regions of reduced density in the main plasmasphere, typically located in the pre-midnight sector. 4) "Shoulders", sharp variations in radial distance of the plasmapause (by ~1/2 RE) in a narrow range of local time. These usually appear in the morning sector. 5) Localized density troughs in the main plasmasphere. 6) Plasma "fingers" extending radially from the brightest parts of the plasmasphere. 7) Wavy plasmapause boundaries, with azimuthal scales of roughly 1 hour in local time. 8) Rapid decreases in the radial distance to the plasmapause, concentrated mainly near the midnight sector. Decreases of 1 RE in 30 minutes have been measured. Generally speaking, these features corotate with the magnetic field as they form and decay. Auroral emissions are also found within the passband of EUV, so that the single data set offers information on plasmasphere-substorm relationships. _______________ Presented at the Fall American Geophysical Union Meeting, San Francisco, CA., December 15-19, 2000