HR: 0800h
AN: SM31A-1221    [Abstracts]
TI: Magnetospheric Radio Tomography: Theory and CLUSTER Experiments
AU: * Zhai, Y
EM: zhaiyh@ee.duke.edu
AF: Duke University, Electrical and Computer Engineering, Duke University, PO Box 90291, Durham, NC 27708 United States
AU: Cummer, S A
EM: cummer@ee.duke.edu
AF: Duke University, Electrical and Computer Engineering, Duke University, PO Box 90291, Durham, NC 27708 United States
AU: Green, J L
EM: James.L.Green@nasa.gov
AF: NASA Goddard Space Flight Center, Code 630, NASA GSFC, Greenbelt, MD 20771 United States
AU: Reinisch, B
EM: Bodo_Reinisch@uml.edu
AF: University of Massachusetts-Lowell, Center for Atmospheric Research, University of Massachusetts-Lowell, Lowell, MA 01854 United States
AU: Christopher, I
EM: ivar-christopher@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, University of Iowa,, Iowa City, IA 52242 United States
AU: Mutel, R L
EM: robert-mutel@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, University of Iowa,, Iowa City, IA 52242 United States
AU: Pickett, J S
EM: pickett@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, University of Iowa,, Iowa City, IA 52242 United States
AU: Gurnett, D A
EM: donald-gurnett@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, University of Iowa,, Iowa City, IA 52242 United States
AU: Escoubet, P
EM: Philippe.Escoubet@esa.int
AF: ESA/ESTEC, ESA/ESTEC, Postbus 299, 2200 AG Noordwijk,The Netherlands, Noordwijk, 299 Netherlands
AB: Recent studies have shown the feasibility and scientific value of radio tomography for remote sensing Earth's magnetosphere. Radio tomography uses radio waves and phenomena known as Faraday rotation and phase/group delay that can be measured to reconstruct full images of electron density and magnetic field. Faraday rotation is the rotation of the polarization of a linearly polarized wave as it travels through the magnetospheric plasma. We present first a flexible and robust direct reconstruction method for magnetospheric radio tomography. We show that for a combined reconstruction of plasma density and magnetic field the direct reconstruction method performs as well as popular iterative methods for large number of satellites, but it performs significantly better when the number of satellites is small. The main advantages of this method are that extra information, such as in situ measurements, can be easily and flexibly incorporated into the reconstruction. We demonstrate the good performance of this method with MHD simulations in reconstructing electron density and magnetic field using constellations of relatively few satellites (11 and fewer) in a single orbit in a variety of magnetospheric regions. To validate the feasibility of the measurements behind radio tomography, we have performed three separate experiments designed using the Radio Plasma Imager (RPI) on the IMAGE spacecraft as the signal source, and the WBD instruments on the four CLUSTER spacecraft as the wave receivers. To measure Faraday rotation of the transmitted wave electric field polarization due to propagation through a magnetized plasma, RPI signals received by WBD instruments in April 2002 and May 2003 were carefully analyzed and interpreted for the three radio tomography experiments. Based on the time-varying spin modulation of the WBD received signals, and their spin-phase difference with the RPI transmitted signal, we report the measured Faraday rotation and the average electron density extracted along the wave propagation path. We demonstrate that the deduced average electron density agrees well with empirical statistical models of the northern polar region.
UR: http://www.ee.duke.edu/~zhaiyh/publication/abstract
DE: 6900 RADIO SCIENCE
DE: 6982 Tomography and imaging
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting