Total expansion factors (f_tot; see Eq. (2)) as a function of latitude at five instants of the cycle (from the top to the bottom panel: t = 0, 2.75 ,3.30, 3.85, 4.40 yr). The field lines and points are coloured as a function of the terminal wind speed (with the same colour table as in Fig. 1). The wind speed is anti-correlated with f_tot for a large fraction of the simulated activity cycle, but the are exceptions. The blue and orange peaks (corresponding to slow and fast wind) in the fourth panel (t = 3.85 yr) show that flux-tubes with equal values of f_tot can bear wind flows with different speeds.