P. H. Reiff, J. L. Green, R. F. Benson, D. L. Carpenter, W. Calvert,
S. F. Fung, D. L. Gallagher, Y. Omura, B. W. Reinisch, M. F. Smith and
W. W. L. Taylor, Remote Sensing Of Substorm Dynamics via Radio
Sounding, presented at the International Conference on Substorms-2,
University of Alaska Fairbanks, AK, March 7-11, 1994.

Remote Sensing Of Substorm Dynamics via Radio Sounding

P. H. Reiff, J. L. Green, R. F. Benson, D. L. Carpenter, W. Calvert,
S. F. Fung, D. L. Gallagher, Y. Omura, B. W. Reinisch, M. F. Smith and
W. W. L. Taylor

ABSTRACT
	This paper describes the technique of magnetospheric radio sounding
and shows how it can be applied to produce "images" of magnetospheric
electron density distributions and their variations during substorms. 
The magnetospheric radio sounder is based on more than a half-century
heritage of ionospheric sounding combined with modern digital
techniques.  Coded pulses are transmitted by a long dipole and the
delay times and directions-of-arrival of the returning pulses are
measured.  Plasma densities from 0.1 to 105 cm-3 can be remotely
sensed simultaneously along several different directions by a digital
sounder operating in the 3 kHz to 3 MHz range.  Positions of
magnetospheric plasma and magnetic boundaries, such as the plasmapause
and magnetopause, can be monitored on a time scale of a few minutes,
and plasmaspheric erosion and refilling quantified during a substorm
cycle.  Such measurements have previously been impossible to obtain. 
From a sounder suitably situated in the near-earth tail lobe, one can
measure the magnetotail cross-section and get information on the field
strength, thus allowing monitoring of total tail flux changes during a
substorm and thus the difference between dayside and nightside merging
rates.  It may also be possible to sound a near-Earth plasmoid
directly and thus sense its position, growth, and motion.