Plasmaspheric Ducted Echoes Observed by the Radio Plasma Imager (RPI) on IMAGE

Shing F. Fung (1),  Robert F. Benson (1), James L. Green (1), Donald L. Carpenter (2), 
Bodo W Reinisch (3) 
(1) Goddard Space Flight Center, NASA, Greenbelt, MD 20771, United States 
(2) STAR Laboratory, Stanford University, Palo Alto, CA 94305, United States 
(3) Center for Atmospheric Research, University of Massachusetts 600 Suffolk Street, 
    Lowell, MA 01854, United States 

Ducted radio echoes similar to those observed in the ionosphere have been observed by the 
Radio Plasma Imager (RPI) aboard the IMAGE satellite, launched on March 25, 2000. During 
passages of the plasmapause and near-equatorial plasmasphere by IMAGE, multiple echoes of 
the RPI transmitted pulses have often been observed. These echoes can be understood as 
radio signals guided by field-aligned plasma density irregularities and reflected at 
plasma cutoffs in the conjugate hemispheres. We will present examples of plasmaspheric 
ducted echoes observed by the RPI at altitudes of a few Earth radii and our interpretation 
of the observations.

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Presented at the Fall American Geophysical Union Meeting, 
San Francisco, CA., December 15-19, 2000