Radio interferometric observations of scattering phenomena in the outer solar corona

Abstract

The Very Large Array was used to observe a number of background radiosources through the solar wind at lambda = 3.6, 6, and 20 cm. The rangeof source elongations was between approximate to 1.7 - 6.5 R-circle dotand source position angles corresponded to both equatorial and polarregions. The angular broadening and scintillation properties of thesources have been used to constrain the spatial power spectrum ofelectron density inhomogeneities in the outer solar corona. The mainresults are: 1) the spatial spectrum is consistent with a power lawPhi(n)(K) proportional to K-alpha-2; 2) Phi(n)(K) is significantlyflatter than ``Kolmogorov{''} with alpha approximate to 1 over spatialscales up to several tens of km; 3) The scattering measure issignificantly higher in the equatorial regions than in polar regions; 4)Phi(n)(K) is highly anisotropic, the inhomogeneities being elongated ina roughly radial direction; 5) the enhanced variance observed invisibility measurements on intermediate time scales - refractivescintillation - is consistent with the spectral constraints deduced fromthe angular broadening observations.