Upper panel: number of PIL pixels for various A_uni bins during periods of low activity (solid line) and high activity (dashed line). Middle panel: number of PIL pixels at a distance smaller than 30 Mm from a filament for various A_uni bins, during periods of low activity (solid line) and high activity (dashed line). The dotted line represents the expected numbers for the high activity period, when using the number of PIL pixels during the high activity period and the proportion of occupied pixels during the low activity period. Lower panel: percentage of occupied PIL pixels (distance smaller than 30 Mm from a filament) during periods of low activity (solid line) and high activity (dashed line).