Radio interferometer measurements of turbulence in the inner solar wind

Details Radio interferometer measurements of turbulence in the inner solar wind Radio interferometer measurements of turbulence in the inner solar wind

Jun 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995sowi.conf...40s&link_type=abstract

Iowa Univ., International Solar Wind 8 Conference, p. 40

Astronomy and Astrophysics

Astronomy

Very Long Base Interferometry, Solar Wind, Plasma Turbulence, Scintillation, Power Spectra, Flux Density, Solar Physics, Solar Diameter, Sun, Radio Astronomy, Wentzel-Kramer-Brillouin Method, Very Long Baseline Array (Vlba), Radio Interferometers, Solar Position, Solar Orbits, Radial Flow, Mathematical Models

Scientific paper

Measurements can be made of Very Long Baseline Interferometer (VLBI) phase scintillations due to plasma turbulence in the solar corona and solar wind. These measurements provide information on the spectrum and intensity of density fluctuations with scale sizes of a few hundred to several thousand kilometers. If we model the spatial power spectrum of the density fluctuations as Pdelta n(q) = C2N q-alpha, where q is the spatial wavenumber, these observations yield both alpha and the path-integrated value of C2N. The recently completed Very Long Baseline Array (VLBA) is capable of making such measurements over the heliocentric distance range from a few solar radii to 60 solar radii and beyond. This permits the determination with the same technique and instrument of the radial evolution of turbulent characteristics, as well as their dependence on solar wind transients, sector structure, etc. In this paper we present measurements of 13 sources observed at a wide range of solar elongations, and at different times. These observations show that the coefficient C2N, depends on heliocentric distance as approximately C2N varies as (R/Solar Radius)-3.7. The radio derived power spectral characteristics are in agreement with in situ measurements by the Helios spacecraft for regions of slow solar wind, but fast solar wind does not have large enough density fluctuations to account for the magnitude of the observed scintillations. The observed radial dependence is consistent with a WKB-type evolution of the turbulence with heliocentric distance. Our data also show indication of turbulence enhancement associated with solar wind transients.

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