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We developed an automated procedure for the identification of transientbrightenings in images from the X-ray telescope on-board Hinode taken with anAl Poly filter in the equatorial coronal holes, polar coronal holes, and thequiet Sun with and without transient coronal holes. We found that in comparisonto the quiet Sun, the boundaries of coronal holes are abundant with brighteningevents including areas inside the coronal holes where closed magnetic fieldstructures are present. The visual analysis of these brightenings revealed thataround 70% of them in equatorial, polar and transient coronal holes and theirboundaries show expanding loop structures and/or collimated outflows. In thequiet Sun only 30% of the brightenings show flows with most of them appearingto be contained in the solar corona by closed magnetic field lines. Thisstrongly suggests that magnetic reconnection of co-spatial open and closedmagnetic field lines creates the necessary conditions for plasma outflows tolarge distances. The ejected plasma always originates from pre-existing ornewly emerging (at X-ray temperatures) bright points. The present studyconfirms our findings that the evolution of loop structures known as coronalbright points is associated with the small-scale changes of coronal holeboundaries. The loop structures show an expansion and eruption with the trappedplasma consequently escaping along the "quasi" open magnetic field lines. Theseejections appear to be triggered by magnetic reconnection, e.g. the so-calledinterchange reconnection between the closed magnetic field lines (BPs) and theopen magnetic field lines of the coronal holes. We suggest that these plasmaoutflows are possibly one of the sources of the slow solar wind.

Coronal hole boundaries evolution at small scales: II. XRT view Can small-scale outflows at CHBs be a source of the slow solar wind?