Panel A: <|B|> averaged over the full disk (μ lower than 0.95) vs. time from 5 min magnetograms. Panel B: filling factor ff, corresponding to a 100 G threshold, vs. time. Panel C: <|B|> averaged over the most quiet 1′ × 3′ box close to disk center along the central meridian; a few outliers above 14 G are not shown for clarity. Panel D: < |B|> averaged over the most quiet 11 × 11 pixels box close to disk center along the central meridian.