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 simila r to 1.5 x 10(6) K. This indicates the existence of electron heating in the source region of the fast solar wind. In this paper, a two-fluid solar win d model, which incorporates additional 'mechanical' heating, is used to inv estigate 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 electr on temperatures predicted by the model to agree with constraints supplied b y both the solar wind ionic charge state data and the solar wind plasma pro perties observed at 1 AU. The corresponding constraints on the coronal elec tron heating will also be discussed.