Density of magnetic elements with lifetimes of > 40 h vs. their average magnetic flux derived for each coronal hole (a). Total unbalanced magnetic flux which arises from these magnetic elements versus the total area they cover (b). Total unbalanced magnetic flux that arises from theses magnetic elements per coronal hole area vs. the absolute mean magnetic field densities of the coronal holes (c). The shaded areas give the 1σ uncertainties of the corresponding fits.