IMAGE-RPI Measurements of Plasmaspheric Electron Density Profiles and Comparisons With 
Plasmaspheric Models and EUV Observations

Leonard N. Garcia (1), Shing F. Fung (2), James L. Green (2), Dennis L. Gallagher (3),
Bill R. Sandel (4), Bodo W. Reinisch (5), and Grigori Khmyrov (5)

(1) Raytheon ITSS/ NASA GSFC, Greenbelt, MD 20771, United States
(2) Goddard Space Flight Center, NASA, Greenbelt, MD 20771, United States
(3) NASA Marshall Space Flight Center, Space Science Department, SD50, Huntsville, AL 35812
(4) University of Arizona, Lunar & Planetary Laboratory, Tucson, AZ  85721
(5) Center for Atmospheric Research, UMass Lowell, MA 01854

The Radio Plasma Imager (RPI) on the IMAGE spacecraft is providing high resolution plasma 
wave measurements throughout its orbit, revealing structural details around times of 
plasmasphere passages. In situ measurements of electron number density (n_e) based on plasma 
thermal emissions and cutoffs of electromagnetic radiation during these passages have been 
obtained for December of 2000. Most of these passages were through the dawn-dusk sectors 
(5-10 and 17-21 MLT). The linear fits of log(n_e)  versus L shell show an average electron 
density profile that lies between the model profiles of Carpenter and Anderson [1992] and 
Gallagher et al. [2000].  Several cases of enhancement or suppression of electron number 
densities across narrow magnetic longitude ranges were also found. These density deviations 
have been compared with outer plasmasphere measurements made by the IMAGE EUV imager and 
may be attributed to radial, co-rotating structures.

Carpenter, D. L. and R. R. Anderson, J. Geophys. Res., 97, 1097, 1992.
Gallagher, D. L., P. D. Craven, and R. H. Comfort, J. Geophys. Res., 105, 18819, 2000.

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Submitted to the Spring 2001 AGU Meeting, Boston, Massachusetts