Angular velocity during the cycle deduced using the sunspot group age selection methodology

Using Greenwich Photoheliographic Results collected during the period 1874-1981 and the Age Selection Methodology (\citet{Zappa-Zucca}), we have studied the variability of the sunspot-groups angular velocity in different phases of the activity cycle. The results indicate that during minima, all sunspot-groups, independently of their age, show the same increase in angular velocity, i.e. ~ 0.16 degrees/day. Comparing our results with those regarding the internal angular velocity as deduced by p-mode oscillations, it is possible to conclude that the observed higher angular velocity during minima concerns several layers beneath the solar photosphere....