Four sets of six subplots, each set corresponding to one epoch (from top to bottom, 2007.59, 2008.09, 2009.46, and 2010.04). For each set, the left subplots contain, from top to bottom, the N_Hα-index (filled circles and left axis) and N_CaIIH-index (crosses and right axis of the top panel of each set), the FeI@846.8404 magnetic line widths (km   s^-1), B_l (Gauss). The right subplots, from top to bottom, correspond to the velocity spans (km   s^-1) obtained from the profile bisectors (Sect. 4.2), the radial velocity (km   s^-1), and the mean unsigned magnetic strength of the total (full line), radial (dashes), azimuthal (dot-dashes) and meridional (dots) magnetic field components extract from the ZDI maps. Error bars are not included whenever they are smaller than the symbol size.