Evolution of the total magnetic flux over cycles 21–24 computed with the new (red) and old (blue) models, as well as the observed flux. For observations, symbols show individual Carrington rotations and observatories, as indicated in the legend, and solid black line shows their average. For the models, means of the daily total magnetic flux over the Carrington rotations are shown, and the contribution of the SSEs is reduced by a factor of 0.4 (see text for details). Panels a,b: use ISN and GSN as input, respectively.