Groups of the most characteristics spectra of Si IV(a) and C II (b). The small panels show the most characteristics spectra in 8 groups for Si IV (a) and 8 groups of C II (b). The blue line indicates the most characteristic profile (the centroid of k-means), the blue-red line indicates the average spectral line profile, and the grey line represents all profiles in the group. The colour of the rectangular box (right top of the spectra panel) indicates the location of the spectrum in the distribution map (top right panel). The white contours of the distribution map represent the ±5 km s⁻¹ plasma flow in Fe XII, thus indicating the position of the upflow region and the active region core.