Radio Remote Sensing of the Solar Wind in the Era of Parker Solar Probe

The NASA Parker Solar Probe mission is providing unprecedented measurements of solar wind plasma and plasma turbulence at heliocentric distances as small as 0.13 AU, or 27 solar radii. Radioastronomical remote sensing measurements of the coronal and solar wind plasma have been made since the 1960s over a heliocentric distance range that overlaps with and extends that of Parker Solar Probe. Much has been deduced from radio observations about the solar wind plasma, primarily the plasma density and turbulent density fluctuations. In this paper I emphasize some results from radioastronomical measurements that pertain to present or future Parker Solar Probe measurements. The radio results may help provide context or independent constraints to the Parker Solar Probe results. This paper will emphasize a comparison between radio scintillation and Parker Solar Probe results on two topics, the heliocentric-distance-dependence of the plasma density variance (where there may be an inconsistency between the two techniques), and the speed at which turbulence density irregularities move radially with respect to the Sun.