Variations of the Internal Asymmetries of Sunspot Groups during Their Decay

Abstract

Abstract The aim of the present study is to show the varying asymmetries during the decay of sunspot groups. The source of input data is the SOHO/MDI-Debrecen Database sunspot catalog that contains the magnetic polarity data for time interval 1996–2010. Several types of asymmetries were examined on the selected sample of 142 sunspot groups. The leading–following asymmetry increases in three phases during the decay and exhibits anticorrelation with size. It is also related to a hemispheric asymmetry: during the decay, the area asymmetry index has higher values in the southern hemisphere, which may be due to the higher activity level in the southern hemisphere in cycle 23. The total umbral area is inversely proportional to the umbra/penumbra ratio, but it is directly proportional to the umbral decay rate. During the decay, the umbra/penumbra (U/P) ratio decreases unambiguously in the trailing parts but in most cases in the leading parts as well. The U/P variation is a consequence of the different depths of umbral and penumbral fields.