Radial dependence of solar wind properties deduced from Helios 1/2 and Pioneer 10/11 radio scattering observations

Radio scattering measurements at 2.3 GHz, conducted over the heliocentric distance range of 1.7 to 180 solar radii, provide data for a study of the radial dependence of the solar wind characteristics. The data are obtained from the Helios 1 and 2 and the Pioneer 10 and 11 spacecraft. Spectral broadening measurements, together with angular broadening data for the spacecraft signal, indicate a value of 24 km/sec for the solar wind velocity at 1.7 solar radii. A velocity profile of the solar wind in the acceleration range is developed. In addition, phase scintillation measurements obtained suggest that the solar wind is slightly converging in the equatorial region between approximately 20 and 180 solar radii.