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

Shing F Fung 1 (301-286-6301; shing.fung@gsfc.nasa.gov)
James L Green 1 
Venku Jayanti 2
Bodo W Reinisch 3
Xueqin Huang 3
William W. L. Taylor 2

1 Space Science Data Operations Office, Goddard Space Flight Center, NASA, Greenbelt, MD 20771
2 Raytheon ITSS/Goddard Space Flight Center, NASA, Greenbelt, MD 20771 
3 Center for Atmospheric Research, UMass Lowell, MA 01854

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 traces of 
echoes of the RPI-transmitted pulses are often observed. These echoes have been attributed 
to the transmitted radio signals being guided by field-aligned plasma density ducts and 
reflected at plasma cutoffs in the local and conjugate polar ionosphere. In this paper, we 
will present examples of plasmaspheric ducted echoes observed by the RPI at altitudes of a 
few Earth radii. Using ray-tracing techniques, we have modeled the characteristics of the 
ducted signals. The modeling results will be used to (1) confirm that the observed echo 
traces are indeed due to ducted signals, (2) produce field-aligned density profiles for 
comparison with profile inversion results and existing plasmaspheric density models, and 
(3) provide insight on plasmaspheric refilling processes.

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Submitted to the Spring 2001 AGU Meeting, Boston, Massachusetts