Top: HMI and AIA observations from one of the data days, 12 June 2014. From left to right: the intensity image at a) the continuum and b) the core of the Fe I 6173 Å line, and c) the AIA 1700 Å channel, d) the longitudinal magnetogram, and e) the map of the image pixels identified as network and faculae (white). The image pixels identified as sunspots are marked in red. The magnetic activity contiguous to sunspots and pores, marked in blue, is excluded from the analysis (see Sect. 3.1). The greyscale is saturated for the intensity images at null and 150% of the quiet-Sun level at disc centre, and at ±50 G for the magnetogram. Bottom: corresponding zoomed-in inset of the boxed 300 × 300 arcsec region.