Taylor, W. W. L., J. L. Green, R. F. Benson, S. F. Fung, M. F. Smith,
W. Calvert, D. L. Carpenter, D. L. Gallagher, B. W. Reinisch, and P.
H. Reiff, Feasibility of the use of radio imaging in magnetospheric
studies, presented at the AGU Spring Meeting, Baltimore, May 23-27,
1994.


Feasibility of the Use of Radio Imaging in Magnetospheric Studies

[*W. W. L. Taylor*] (Nichols Research Corporation, Arlington, VA
22209;
ph. 703-527-2410; Internet: taylor@ncf.gsfc.nasa.gov); J. L. Green,
R. F. Benson, S. F. Fung, M. F. Smith (all at Goddard Space Flight
Center); W. Calvert (University of Iowa); D. L. Carpenter (Stanford
University); D. L. Gallagher (Marshall Space Flight Center); B. W.
Reinisch (University of Massachusetts, Lowell); P. H. Reiff (Rice
University)

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. An exciting new type of magnetospheric imaging, radio
plasma imaging, will allow large portions of the magnetosphere to be
imaged and studied. 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.

A magnetospheric radio plasma imager will transmit short electro-
magnetic pulses at frequencies from about 3 kHz to 3 MHz and receives
their echoes, like a radar. This magnetospheric radio imager will
have much greater capability than the earlier ionospheric topside
sounders. Like advanced design ground-based digital ionosondes, it
will be able to measure phase, Doppler shift, polarization, and
direction of arrival in addition to the amplitude and time delay of a
signal at a given frequency. Sky maps of ionization structures in the
magnetosphere similar to those obtained in the ionosphere by modern
ground based sounders will be obtained.

To see how the extension of the ionosphere sounder to the
magnetosphere will work and what kind of data will be available, a
comprehensive magnetospheric model, a model of a realistic radio
plasma sounder, and a ray tracing code have been coupled. The results
are simulated magnetospheric plasmagrams, which are plots of echo
power and delay as a function of wave frequency. These plasmagrams
show what parts of the magnetosphere can be studied from each point
along a satellite orbit, how the echo power compares to the receiver
and cosmic noise, and how sophisticated signal encoding and data
analysis techniques allows probing of these distant plasma regimes
with very low signal power.