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The IMAGE Extreme Ultraviolet Imager (EUV) provides our first global images of the plasmasphere by imaging the distribution of He+ in its 30.4-nm resonance line. The images reveal the details of a highly structured and dynamic entity. Comparing EUV images and selected in-situ observations has helped to validate the remote sensing measurements. The brightness in the EUV images is heavily weighted by the He+ density near the plane of the magnetic equator, but two lines of evidence emphasize that the features seen by EUV extend far from the equator, and in at least some cases reach the ionosphere. Certain features and behaviors, including shoulders, channels, notches, and plasma erosion events, appear frequently in the EUV images. These are keys to understanding the ways that electric fields in the inner magnetosphere affect the large and meso-scale distribution of plasma, and their study can elucidate the mechanisms by which the solar wind and interplanetary magnetic field couple to the inner magnetosphere. [ABSTRACT FROM AUTHOR]

Simultaneous IMAGE EUV plasmaspheric images and Magneto spheric Plasma Analyzer (MPA) data from the Los Alamos National Laboratory's geosynchronous satellites are combined to understand plasmaspheric behavior and to quantify the global images. A brief review of the understanding of the plasmasphere as learned from in situ observations prior to the launch of IMAGE is given to place the results presented here into context. [ABSTRACT FROM AUTHOR]