Green, J. L., Radio Remote Sensing of Magnetospheric Plasmas,
presented at the AGU Spring Meeting, Baltimore, May 23-27, 1994.

Radio Remote Sensing of Magnetospheric Plasmas

J L Green (NASA Goddard Space Flight Center, Greenbelt, MD 20771;
green@nssdca.gsfc.nasa.gov)

Due to recent advances in radio sounder design and
instrumentation, it is becoming feasible to perform remote radio
sounding of the magnetosphere by using techniques perfected for
ionospheric studies.  Like ionospheric sounding, free-space
electromagnetic waves at 3 kHz to 1 MHz, launched from a space-
based sounder within the magnetospheric low density cavity will
reflect specularly at their cutoffs where the local refractive indices
vanish. The locations and plasma parameters of the remote
reflection points can be derived from the measurements of the
delay times and frequencies of the returned echoes. From a sounder
situated outside the plasmasphere, it will be possible to probe and
monitor the structure and dynamics as well as the global
configuration of many magnetospheric boundaries such as the
plasmapause and the magnetopause thereby yielding much
information on the dynamic coupling between the solar wind and
the magnetosphere. Furthermore, it will be shown that observations
of swept-frequency radio echoes arriving from different directions
can be used to determine important three-dimensional plasma
structures.

This talk will discuss the current limitations of magnetospheric
sounding and show the results of various simulations using ray
tracing calculations within a model magnetosphere.  The radio
sounding technique provides a truly exciting opportunity to study
global magnetospheric dynamics in a way never before possible.