Green, J. L., W. W. Taylor, S. F. Fung, R. F. Benson, W. Calvert, B.
W. Reinisch, D. L. Gallagher, and P. Reiff, Radio remote sensing of
magnetospheric plasmas, Chapman Conference on Measurement Technique
for Space Plasmas, Santa Fe, New Mexico, April 3-7, 1995.

Radio remote sensing of magnetospheric plasmas

James L. Green, William W. L. Taylor, Shing F. Fung, Robert F. Benson,
Wynne Calvert, Bodo Reinisch, Dennis Gallagher, and Patricia Reiff

With recent advances in radio transmitter and receiver design, and
modern digital processing techniques it has become feasible to perform
remote radio sounding of the magnetosphere utilizing methods perfected
for ionospheric sounding more than three decades ago. Like ionospheric
sounding, free-space electromagnetic waves, launched within a lower
density region will reflect at the plasma cutoffs. The location and
characteristics of the plasma at a remote reflection point can then be
derived from measurements of the delay time, frequency, and direction
of an echo. The characteristic of large scale ionospheric disturbances
can be displayed in skymaps, Doppler maps, and other useful images
from the hundreds of echoes which are detected by this technique. In
an analogous way, similar images of the magnetosphere at radio
frequencies could be obtained. A magnetospheric radio imager,
operating at frequencies between 3 kHz to 3 MHz would provide
quantitative electron density profiles simultaneously in several
different directions on a time scale of minutes or less. From an
imager situated in the magnetospheric density cavity, it would be
possible to observe the structure and dynamics of many different
magnetospheric boundaries at the same time. Simulations of these
observations have been done on specific radio imager characteristics
and extensive ray tracing calculations. The radio imaging technique
provides a truly exciting opportunity to study global magnetospheric
dynamics in a way which was never before possible.