Comparisons of IMAGE RPI and EUV Observations of Longitudinal Electron
Density Structures in the Plasmasphere

Leonard N. Garcia 
  Raytheon ITSS/ NASA GSFC, Greenbelt, MD 
Shing F. Fung, James. L. Green
  NASA GSFC, Greenbelt, MD 
Dennis L. Gallagher
  NASA MSFC, Huntsville, AL 
Bill R. Sandel
  University of Arizona, Lunar & Planetary Laboratory, Tucson, AZ  
Bodo W. Reinisch, Ivan Galkin, Grigori Khmyrov
  Center for Atmospheric Research, University of Massachusetts, Lowell,  MA

The Radio Plasma Imager (RPI) on the IMAGE spacecraft launched March 25,
2000 is providing high resolution plasma wave measurements throughout
its orbit. In situ measurements of electron number density based on
plasma quasi-thermal noise emissions and cutoffs of electromagnetic
radiation in 2000 have been screened. The plasma line seen in the
passive RPI observations reveal longitudinal electron plasma structures
around times of plasmasphere passage. Several cases of enhancement and
suppression of electron number densities across narrow magnetic
longitude ranges within the outer plasmasphere were found. These density
structures appear to be associated with previously observed radial,
co-rotating enhanced density finger-like structures seen in the global
plasmasphere images made by the IMAGE EUV imager. In this paper, we will
present cases of the plasma structures observed by RPI and show their
correlation with features seen in corresponding EUV images.