Long-term temporal variations in the mean maximum size of sunspot groups

Javaraiah Javaraiah, jj@iiap.res.in, Indian Institute of Astrophysics, Bangalore-560034, India

Abstract
We have analysed the combined Greenwich and Solar Optical Observatory sunspot group data during the period 1874-2011 and found some systematic long-term trends in the temporal variations of the mean sizes of the small (maximum area $A_M < 100$ millionth of solar hemisphere, msh), large ($100 \ge A_M < 300$ msh), and big ($A_M \ge 300$ msh) spot groups. That is, our analysis suggest that there exists a strong trend of a approximate 130-year cycle in the variation of the mean size of the small groups, whereas there is a suggestion of the existence of approximate 44-year cycles in the variations of the mean sizes of the large and big groups. The variation in the mean size of the all groups (combination of the aforesaid three classes of groups) is also showed the existence of approximate 44-year cycles in it. The corresponding frequencies of the 130-year and 44-year cycles may be represent the sub-harmonics of the 22-year solar magnetic cycle. The mean rotation rate of the large groups is relatively slower than that of the small groups, suggesting that the mean rotation rates of the large and the small groups may be related to the rotation rates of somewhat deeper and sallower layers of the Sun's convection zone, respectively. Thus, the aforementioned approximate 130-year and 44-year cycles may be related to the long-term dynamic changes in the sallower and deeper layers of the Sun's connection zone, respectively.