Quasi-periodicities of Sunspot Area Fluctuations

Ryszarda Getko

Astronomical Institute, University of Wroclaw

The sunspot area fluctuations over the epoch of 12 solar cycles (12-23) are investigated. I apply auto-correlation and wavelet analyses to the sunspot area fluctuations and their transformations with a constant variance for the northern and the southern hemispheres of the Sun. Because of the asymmetry of the fluctuation probability distribution, the positive and the negative fluctuations are considered separately. For positive fluctuations the auto-correlation analysis shows three statistically significant quasi-periodicities at about 10, 17 and 23 solar rotations. For more than 50% of solar cycles in each hemisphere two last quasi-periods (17 and 23 rotations) can be represented as the multiple of the shortest quasi-period (from the interval [7, 13] rotations). The wavelet analysis gives the same results as the auto-correlation analysis for the shortest quasi-period. For the fluctuation time series the correlation coefficient between these ewavelet and the auto-correlation results is about 0.9 for 87% of the auto-correlation peaks. For the positive fluctuation time series it is also 0.9 for 72% of the auto-correlation peaks.