Top panel: same as Fig. 3, but this time the periodogram for July 2008 (green line) is compared to a shuffled data set, in which each individual Stokes V profile has been randomly associated to the Julian date of another profile of the same time-series (black line). Middle panel: same as the upper part of the plot, but with observations of September 2009 (red line) and their shuffled counterpart (black line). Bottom panel: same as Fig. 3, but using two sets of fake Stokes V profiles computed by ZDI using our time-sampling of July 2008 and September 2009 (green and red lines, respectively).