HR: 17:45h
AN: SH42E-08 INVITED     [PDF]
TI: Radio Astronomy and the Structure of the Interplanetary Medium
AU: * Spangler, S R
EM: steven-spangler@uiowa.edu
AF: Dept. of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 United States
AB: Radioastronomical remote sensing measurements provide one of the few ways of diagnosing the coronal and solar wind plasma from the inner corona to the limit of in-situ measurements (0.28 a.u.). This talk concentrates on results from observations of extragalactic radio sources (radio galaxies and quasars) viewed through the corona and solar wind. Measurements have been made of the fluctuations in brightness of these sources (intensity scintillations), blurring due to plasma turbulence (angular broadening), and turbulence-induced fluctuations in the phase of an interferometer. Depending on the instrument used and the frequency of observation, the heliosphere can be probed from heliocentric distances of about 2 solar radii to greater than 0.5 a.u. Results of such observations have been determination of the flow speed of the solar wind for both fast and slow streams in regions of the heliosphere not accessible to direct measurement, the evolution of the intensity of the turbulence with heliocentric distance, limits on the speed with which the turbulence propagates with respect to the solar wind fluid, enhancements of turbulence in the vicinity of coronal mass ejections, the magnitude of plasma velocity fluctuations (and therefore magnetic field fluctuations) as a function of heliocentric distance, the magnitude of the large scale coronal magnetic field, and properties of irregularities in that field. In my opinion, the most important future contribution of this type of measurement will be to determine the level and spectral characteristics of magnetic field and velocity fluctuations in the inner heliosphere (within a heliocentric distance of 0.3 astronomical units) and the relationship of those fluctuations to the large scale solar wind stream structure.
DE: 2139 Interplanetary shocks
DE: 2149 MHD waves and turbulence
DE: 2159 Plasma waves and turbulence
DE: 2164 Solar wind plasma
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting