The two components in the distribution of sunspot groups with respect to their maximum areas

Abstract

From an analysis of the distribution of sunspot groups with respect to their maximum areas we find that this distribution consists of two distinct components. One component contributes to spot groups of all possible values of A* with a distribution density varying as ∼ exp (b1 a*1/2) with b1 nearly constant from cycleto cycle and having a mean value ∼10-4 km-1. The other component is predominantly responsible for spot groups withA* ≲, 30 *10-6 hemisphere but may provide a few spot groups even above 50 * l0-6 hemisphere. This component may follow a distribution density ∼ exp (-b2 A*). We also determine the widths of the latitude zones over which spot groups in various intervals of A* appear and study their variation with time. These widths and their variations indicate that the two statistical samples of spot groups may be produced by two families of flux-tube clusters as suggested earlier in a phenomenological model. Very thin flux-tube clusters in the statistical samples seem to be related to the ephemeral active regions and X-ray bright points.