Density Fluctuations in the Solar Wind Deduced from Radio Measurements by Parker Solar Probe

Radio waves are strongly scattered in the solar wind, so that their apparent sources seem to be considerably larger and shifted compared to the actual sources. Since the effect of radio wave scattering depends on the spectrum of density turbulence, better understanding of the radio wave propagation provides indirect information on the density fluctuations. Here, we have analyzed 30 type III bursts detected by Parker Solar Probe to retrieve decay times as a function of frequency. We observed a significant deviation for frequencies above 1 MHz when compared to previous observations by the STEREO spacecraft. Next, we performed Monte Carlo simulations to study the role of scattering on time-frequency profiles of radio emissions. By comparing Parker Solar Probe observations and Monte Carlo simulations we predicted relative density fluctuations between 2.5 and 14 solar radii. Finally, we calculated relative density fluctuations measured in situ by Parker Solar Probe at characteristic scale times of Monte Carlo simulations during the perihelion #1 and perihelion #2, and compared them with STEREO predictions.