An Overview of IMAGE/RPI Observations

James Green
NASA/GSFC, Code 630

The Radio Plasma Imager (RPI) on the Imager for Magnetopause-to-Aurora Global
Exploration (IMAGE) spacecraft was designed as a long-range magnetospheric radio
sounder, relaxation sounder, and a passive plasma wave instrument.  The RPI is a
highly flexible instrument that can be programmed to perform these types of
measurements at times when IMAGE is located in key regions of the magnetosphere.
 RPI is the first radio sounder ever flown to large radial distances into the
magnetosphere.

The long-range sounder echoes from RPI allows for the remote sensing of a
variety of plasmas structures and boundaries in the magnetosphere.  A profile
inversion technique for RPI echoes has been developed and provides a method for
determining the density distribution of the plasma from either direct or
field-aligned echoes.  This technique has enabled the determination of the
evolving density structure of the polar cap and the plasmasphere under a variety
of geomagnetic conditions.   Results in the plasmasphere and in the polar cap
will be discussed.  

Plasmaspheric measurements from RPI have been compared extensively with the
Extreme Ultraviolet  (EUV) Imager on IMAGE resulting in a number of new
discoveries. For instance, these combined observations show that kilometric
continuum is generated at the plasmapause, from sources in or very near the
magnetic equator, within a bite-out region of the plasmasphere. The process by
which plasmaspheric notch structures are produced is not completely understood
at this time.

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Poster and Tea Seminar, Goddard Space Flight Center, 16 September 2003.