Comparison between the average (top) and standard deviation (bottom) values of the APs computed from 4-year segments. In the left panels, the blue symbols correspond to the S​_ph⊙, while the green and orange solid lines concern the scaled SA and F_10.7, respectively. The right-hand panels show their distributions. “24yr” denotes 24 years, i.e., the two last solar cycles, while “70yr” and “140yr” denote 70 and 140 years.