On the Electron Temperature and Coronal Heating in the Fast Solar Wind Constrained by In-situ Observations

The electron temperature profile in the polar coronal hole inferred by the ionic charge state data of the fast wind exhibits a local maximum of 1:5 10 K. This indicates the existence of electron heating in the source region of the fast solar wind. In this paper, a two-fluid solar wind model, which incorporates additional ‘mechanical’ heating, is used to investigate the heating of the electrons in the coronal hole. We find that the classical collision-dominated description for the electron conduction heat flux is not valid and needs to be severely limited in order for the electron temperatures predicted by the model to agree with constraints supplied by both the solar wind ionic charge state data and the solar wind plasma properties observed at 1 AU. The corresponding constraints on the coronal electron heating will also be discussed.