Alfvenic slow solar wind and proton temperature anisotropy in inner heliosphere by PSP observations
Résumé
We use Parker Solar Probe (PSP) observations to investigate two aspects of the inner heliosphere solar wind: (1) Alfvenic slow wind and (2) proton temperature anisotropy . (1) Slow solar wind is generally found to have low Alfvenicity, but PSP observed mainly slow solar wind with high Alfvenicity during its first two encounters. Based on PSP measurements, we study the characteristics of Alfvenic slow solar wind near the Sun, in particular the variation of helium abundance and proton temperature anisotropy. (2) We fit the proton temperature anisotropy using SWEAP and magnetic field observations from the FIELDS instrument suite. Accordingly, we study the temperature anisotropy variations as a function of plasma beta, heliocentric distance, and different solar wind stream. These results may lead to some new understandings of solar wind origin and evolution.