Fung, S. F., J. L. Green, P. H. Reiff, C. B. Boyle, and W. W. L.
Taylor, Probing the Terrestrial Ring Current by the Radio Sounding
Technique:  A Model Study, presented at the Spring AGU Meeting,
Baltimore, Maryland, May 30-June 2, 1995.

Probing the Terrestrial Ring Current by the Radio Sounding Technique: 
A Model Study

S F Fung (NASA GSFC, Space Physics Data Facility Code 632,
Greenbelt, MD 20771 (fung@nssdca.gsfc.nasa.gov), J L Green}, NASA
GSFC, Space Science Data Operations Office, Code 630, Greenbelt, MD
20771 (green@nssdca.gsfc.nasa.gov), P H Reiff, Department of Space
Physics and Astronomy, Rice University, Houston, TX 77005
(reiff@alfven.rice.edu), C B Boyle, Department of Space Physics and
Astronomy, Rice University, Houston, TX 77005 (boyle@alfven.rice.edu),
W W L Taylor, Nichols Research Corp, Arlington, VA 22209
(taylor@nssdca.gsfc.nasa.gov)

The terrestrial ring current has been recognized to play a major role
in geomagnetic storm/substorm electrodynamics since the early
ground-based magnetometer observations. Subsequent space-based in situ
plasma measurements such as those from the AMPTE mission, have
provided important information, e.g. energies, charge states, and
composition, on the ring current carriers. Nevertheless, very little
is known with regard to the development and decay of the global ring
current system and their effects on the magnetospheric dynamics. The
radio sounding technique, which has been advanced for ionospheric
studies in the last few decades, can provide a new approach for
magnetospheric investigations. In this paper, we explore the
possibility of probing the terrestrial ring current by the radio
sounding technique. Using ray tracing model calculations, we will
investigate the radio echo characteristics associated with the ring
current and thus show that the radio sounding technique can be used to
probe the magnetospheric density and current structures.