Presentation #405.05 in the session “The Sun and The Solar System”.
During the recent COVID-19 pandemic period, multi-frequency interplanetary scintillation (IPS) observations have been made using the highly sensitive 305-m Arecibo Radio Telescope with the goals to study the three-dimensional distribution of near-Sun solar wind at the minimum phase of the current solar cycle and also to track space weather events (e.g., coronal mass ejections) from the Sun to the orbit of the Earth. These observations have been made in the frequency ranges of 327 MHz, L, S, and C bands. For example, the 327-MHz observations have been useful to probe the speed and density turbulence of the solar wind at distances greater than 40 solar radii. On the other hand, the high-frequency measurements have been extremely useful to study the characteristics of the solar wind at distances less than 40 solar radii, where the acceleration of the solar wind is effective. In this talk, we report the results on the radial changes of the spatial anisotropy observed in the solar wind plasma as a function of observing frequency and these results are compared with the results of the typical random plasma turbulence (e.g., Kolmogorov type of turbulence). These findings along with the results from the Ooty Radio Telescope are also useful in constraining the dissipation scale of the solar wind plasma.