Changes in sunspots angular velocity and phase of the solar cycle

We have analyzed the sunspot-groups data for the period 1874-1981 (Greenwich Pho- toheliographic Results) using the age selection methodology (Zappala and Zuccarello, 1991) and taking into account the Sporer law, in order to investigate the variability of the solar angular velocity during the activity cycle. We have found that the equatorial velocity deduced by young sunspot-groups (YSG) is always higher (> 2.7%) than that deduced by all sunspot-groups (ASG) and that it increases during minima, when it may be ~ 5% higher than the mean angular velocity deduced by ASG. From the comparison of our results with those reported in literature (Gilman and Howard, 1984) and taking into account the internal angular velocity as deduced by p-mode oscillations, we suggest that the observed higher angular velocity of the Sun during the minima is not only due to the presence, in this phase of the cycle, of a greater number of young (and faster) sunspot-groups, but also to a positive acceleration concerning deeper layers of the Sun.