Energy transfer of the solar wind turbulence based on Parker solar probe and other spacecraft observations

The supersonic solar wind, first predicted by Parker and then observed by Mariners, extends to form a heliosphere around the Sun. The energy supply from the energy containing range, the energy cascade though the inertial range, and the eventual energy dissipation are three basic processes of the energy transfer in the solar wind and have been studied for a long time. However, some basic issues remain to be discovered. Here, we review the recent progress in the mechanisms of energy transfer of the solar wind turbulence from the observational perspective. Based on the Parker solar probe observations, the energy supply mechanism by the low-frequency break sweeping is proposed to provide enough energy for the proton heating in the slow solar wind. This mechanism also works in the fast solar wind. The energy flux by the low-frequency break sweeping is consistent with that by the classical von Kármán decay mechanism. For the energy cascade in the inertial range, the scaling behavior of the third-order structure functions demonstrates the effect of the complex dynamics of the solar wind. The process of energy transfer is fundamental to understand the solar wind turbulence and help to construct the model of the space environment.