The Waldmeier Effect for Two Sunspot Populations

Abstract

This paper continues our studies in which we showed that sunspot groups form two populations differing by physical properties—populations of small and large groups. The known Waldmeier effect has been individually considered for these populations. Two formulations of this effect were verified: the classical one, which connects the solar activity index at the maximum of the 11-year cycle with the length of the ascending phase of a cycle, and the modified one, connecting the index value at the cycle maximum with the highest rate of the index change along the ascending branch. We used the data from the Greenwich Observatory and the Kislovodsk Mountain Astronomical Station for the solar activity cycles from 12 to 24 to construct the series of indices for the areas and the numbers of sunspot groups. It has been shown that the Waldmeier effect works more strictly for the population of large sunspot groups than for that of small groups. The results of this analysis may find an application in the dynamo theory.