Scatterplot of the absolute value of the signed mean magnetic flux density of CHs as a function of the CH area. Top panel: all observations (in red the average values over each evolution). Middle panel: evolution of each CH individually. Bottom panel: correlation between change in area and change in magnetic flux density for each CH evolution individually. Middle and bottom panels: the median of the bootstrapped sample for each evolution is represented by the horizontal line in the bar, the green and blue bars represent the 80% percentiles, and the whiskers the 90% percentiles. The dotted line gives the mean of the median values.