a) Maximum negative velocities during the first 12 h of the emergence of active regions versus the heliocentric angle that corresponds to the position of the active regions at this point in time. Diamonds mark normal active regions; black squares mark reverse ones. The solid line corresponds to the nonlinear regress Eq. (2); dotted lines correspond to 99% confidence intervals for the means. b) Maximum negative velocities of convective flows in the quiet Sun versus the heliocentric angle.