Investigations of Irregularities in Remote Plasma Regions by Radio Sounding:
Applications of the Radio Plasma Imager on IMAGE

Shing F. Fung, Robert F. Benson
NASA Goddard Space Flight Center, Greenbelt, MD

Donald L. Carpenter
Stanford University, Palo Alto, CA

Bodo W. Reinisch
University of Massachusetts, Lowell, MA

Dennis L. Gallagher
NASA Marshall Space Flight Center, Huntsville, AL

            The Radio Plasma Imager (RPI) on the IMAGE mission operates like a
radar by transmitting and receiving coherent electromagnetic pulses. The RPI is
designed to receive mirror-like (specular) reflections and coherent scatter
returns. Long-range echoes of electromagnetic sounder waves are reflected at
remote plasma cutoffs. Thus, analyses of RPI observations will yield the plasma
parameters and distances to the remote reflection points. The RPI will employ
pulse compression and spectral integration techniques, perfected in ground-based
ionospheric digital sounders, in order to enhance the signal-to-noise ratio in
long-range magnetospheric sounding. When plasma irregularities exist in the
remote magnetospheric plasmas being probed by the sounder waves, echo signatures
may become complicated. Experience in ionospheric sounding under such conditions
indicates that sounding echo strengths can actually be enhanced by the presence
of irregularities, and ground-based sounding indicates that coherent detection
techniques can still be employed. In this paper we investigate the conditions
that will allow coherent signals to be detected by the RPI and the signatures of
scattering to be expected in the presence of multi-scale irregularities.
Sounding of irregular plasma structures in the plasmasphere, plasmapause and
magnetopause are also discussed.

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Space Science Reviews, IMAGE Special Issue, Vol. 91, pp. 391-419, February, 2000