Radio synthesis imaging of scatter-broadening at small solar elongations

Abstract

When the lines of sight to distant radio sources pass close to the Sun, the radiation from the source undergoes scattering due to electron density irregularities in the outflowing solar wind plasma and phenomenon such as intensity scintillations and angular broadening can be observed. At small solar elongations (E < 4°) the scattering is sufficiently strong that the scatter-broadened image can be resolved using radio synthesis arrays such as the VLA1. The measured visibilities and the reconstructed image can be used to study the turbulence spectrum and anisotropy in the solar wind. We present here some results of observations of three strong radio sources at several elongations in the range 0.5°- 4° using the A-configuration of the VLA (maximum baseline 35 km) at wavelengths of 2,3.5,6, and 20cm.