Panel A): average magnetic flux over the disk (daily values) versus time (years), in ppm of the solar hemisphere. Dots in red correspond to the time series studied in Sect. 4 (days for which we know the filament coverage) and dots in black correspond to the full time series studied in Sect. 5 (study of the magnetograms only). Panel B): same for the number of PIL pixels. Panel C): same for the average A_uni. Panel D): same for the average D_uni. Panel E): same for the average ∇B_pil. Panel F): same for the Ca plage filling factor (from Meunier & Delfosse 2009). Panel G): same for the surface coverage of the filaments, in ppm of the solar hemisphere. Panel H): same for the percentage of occupied PIL pixels, corresponding to PIL pixels that are at a distance smaller than 30 Mm from a filament.