Close relation between solar wind acceleration and density turbulence revealed from IPS observations


Interplanetary scintillation (IPS) observations of natural radio sources have been conducted at study the solar wind. The computer-assisted tomography of IPS observations enables determination of global distribution of the solar wind speed. It is demonstrated from ISEE IPS observations collected between 1985 and 2019 that the large-scale structure of the solar wind drastically changes with the solar cycle. In this study, a systematic discrepancy in the solar wind speed was found from comparison between IPS and in situ observations, and it was ascribed to the effect of long-term change in the property of solar wind density turbulence. This result suggests close relation between the efficiency of solar wind acceleration and density turbulence, which depends on long-term variation of the solar activity, and it is considered as an important clue to elucidate the mystery of solar wind acceleration.

Tokumaru, M., K. Fujiki, M. Kojima, and K. Iwai, Global distribution of the solar wind speed reconstructed from improved tomographic analaysis of interplanetary scintillation observations between 1985 and 2019, Astrophysical Journal, 922:73 (18pp), 2021,

Global distribution of the solar wind speed derived from ISEE IPS observations between 1985 and 2019 (Tokumaru et al., 2021)