Variations and Regularities in the Hemispheric Distributions in Sunspot Groups of Various Classes

Abstract

The present study investigates the variations and regularities in the distributions in sunspot groups (SGs) of various classes in the northern and southern hemispheres from Solar Cycles (SCs) 12 to 23. Here, we use the separation scheme that was introduced by Gao, Li, and Li (Solar Phys.292, 124, 2017), which is based on $A/U$ (A is the corrected area of the SG, and U is the corrected umbral area of the SG), in order to separate SGs into simple SGs ($A/U \leq 4.5$) and complex SGs ($A/U > 6.2$). The time series of Greenwich photoheliographic results from 1875 to 1976 (corresponding to complete SCs 12 – 20) and Debrecen photoheliographic data during the period 1974 – 2015 (corresponding to complete SCs 21 – 23) are used to show the distributions of simple and complex SGs in the northern and southern hemispheres. The main results we obtain are reported as follows: i) the larger of the maximum annual simple SG numbers in the two hemispheres and the larger of the maximum annual complex SG numbers in the two hemispheres occur in different hemispheres during SCs 12, 14, 18, and 19; ii) the relative changing trends of two curves – cumulative SG numbers in the northern and southern hemispheres – for simple SGs are different from those for complex SGs during SCs 12, 14, 18, and 21; and iii) there are discrepancies between the dominant hemispheres of simple and complex SGs for SCs 12, 14, 18, and 21.