Coronal plumes and the expansion of pressure balanced structures in the fast solar wind

The expansion of a coronal hole filled with a discrete number of higher density filaments (plumes) in overall pressure balance with the ambient medium is described within the thin flux tube approximation. The resulting solar wind model extends the results of Parker (1964) and Velli et al. (1994) to non-isothermal temperature profiles and includes a flux of Alfvén waves propagating both inside and outside the structures. Remote sensing and solar wind in situ observations are used to constrain the parameter range of our study. Possible candidates to be the remnants of plumes in the polar high-speed solar wind are pressure balanced structures (PBS) and/or microstreams.