Scatter plots between different observables for various OPUs and comparison with the penumbra of a sunspot. Top: Scatter plot between v_LOS and B_LOS. Bottom:B vs. I_c. The different colours correspond to the individual OPUs shown in Fig. 1 (indicated by the red contours in that figure). The black contours represent the 2D kernel density estimates of the respective observables for the penumbra of the sunspot shown in the rightmost column of Fig. 1, with 99%, 90%, and 50% of the distribution being within the respective contours. We adjusted the B_LOS polarity associated with the heads of filaments to be positive in the individual OPUs for a better comparison. The scatter plot in the top panel only includes pixels in which B > 500 G to exclude surrounding patches of plage.