Heating Energy Supply Mechanisms in the Slow Solar Wind inside 0.3 au

The slow solar wind has been found to expand adiabatically outside 0.3 au in the inner heliosphere based on Helios observation. It has recently reported that inside 0.3 au, the slow wind experiences stronger perpendicular heating compared to the outside. Stochastic heating is introduced to explain its observational heating rate as a description of the heating process. However, it remains a question which one can be applied to the slow solar wind among the several possible models describing the energy supply processes. Here we utilize the measurements obtained by Parker Solar Probe during its first three encounters and analyze the temperature and heating rate profile for slow solar wind with respect to the radial distance inside 0.3 au. We find that the heating rate profile of slow solar wind inside 0.3 au is comparable with the expected profile of the fast solar wind based on the Helios observation outside. We also calculate corresponding theoretical heating rates profiles for several mechanisms and compare them with the observation. We discuss those mechanisms providing the energy sources. Our results promote our understanding of slow solar wind heating inside 0.3 au.