Radio Tomography Experiments with IMAGE, WIND, and Cluster

S.A. Cummer, J.L. Green, B.W. Reinisch, M.L. Kaiser, M.J. Reiner, 
R. Manning, K. Goetz, I. Christopher, R. Mutel, J. Pickett, 
D.A. Gurnett, and P. Escoubet


To validate and demonstrate the potential of magnetospheric radio
tomography, we have performed three separate experiments using the
Radio Plasma Imager (RPI) on the IMAGE spacecraft as the signal
source.  The WAVES instrument on WIND and the WBD instruments on the
four Cluster spacecraft have been the wave receivers.  These
experiments were designed to measure the Faraday rotation of the
transmitted wave polarization created through propagation through a
magnetized plasma.  In the proper frequency range, Faraday rotation
is proportional to the path-integrated product of the magnetospheric
electron density and magnetic field, enabling large-scale
measurements of these quantities on the single paths of these
experiments.  In August 2000, WAVES received a single frequency (828
kHz) RPI transmission.  In October through December 2001, WAVES
received two frequency (508 and 828 kHz) RPI transmissions.  And in
April 2002, WBD on Cluster received stepped frequency (between 100
kHz and 500 kHz) RPI transmissions.  These RPI signals have been
measured on propagation paths longer than 10 Re. By exploiting the
time variation and frequency dependence of Faraday rotation, the
integrated electron density/magnetic field product has been measured,
with some limitations, in each of these experiments. We report on the
novel large scale magnetospheric plasma and magnetic field
measurements generated by each of these radio propagation
experiments.  We also demonstrate, through these measurements, what
quantities can be measured and how best to measure them on a
dedicated radio tomography mission.

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Fall 2002 Meeting of the American Geophysical Union
San Francisco, CA, USA, 6-10 December 2002