Taylor, W. W. L., Benson, R. F., W. Calvert, D. L. Carpenter, S. F.
Fung, D. L. Gallagher, J. L. Green, P. H. Reiff, B. W. Reinisch, and
M. F. Smith, Radio sounding of the magnetosphere: overview, presented
at the National Radio Science Meeting (URSI), University of Colorado
at Boulder, Boulder, Colorado, January 3-7, 1994.

RADIO SOUNDING OF THE MAGNETOSPHERE

W. W. L. Taylor (Nichols Research Corporation, 1700 N. Moore St.,
Suite 1820, Arlington, VA 22209, USA) and the Radio Plasma Sounding
Team

        Over the past few years the ad hoc Radio Plasma Sounding Team
has investigated the possibility of using radio waves to image the
magnetosphere. In the thirty five years of space physics research,
ionosondes, auroral and geocorona instruments, and energetic neutral
detectors have been able to remotely sense some parts of the
magnetosphere and ionosphere. A new type of magnetospheric imaging,
radio plasma imaging will allow large portions of the magnetosphere to
be studied, using data taken over only a few hours. For example, the
dynamics of the plasmapause and magnetopause will be able to be
investigated because remote imaging will allow the investigator to
visualize the surfaces, not just make single point measurements while
passing through the surfaces.        
	Radio sounding will be reviewed, along with the ionospheric
understanding that ground based and topside sounders have brought us
over the years. Ground based (bottomside) sounders were necessary to
the understanding of the lower ionosphere as topside (satellite)
sounders were to the upper ionosphere.
         To see how the extension of the ionosphere sounder to the
magnetosphere will work and what kind of data will be available, the
Team has assembled a comprehensive magnetospheric model and coupled it
with a model of a realistic radio plasma sounder, and a ray tracing
code. The results give simulated magnetospheric plasmagrams, which are
plots of echo delay as a function of wave frequency.