Asymmetry Analysis of Solar Northern and Southern Hemisphere Rieger-type Period Based on CEEMD-SSWT

CEEMD (Complete Ensemble Empirical Mode Decomposition) is an adaptive filtering algorithm proposed in recent years, and SSWT (Synchrosqueezed Wavelet Transform) is a current high-resolution time-frequency analysis algorithm. In this paper, CEEMD is used to pre-filter the sunspot daily area data, and then SSWT is used to analyze the Rieger-type period asymmetry of the northern and southern hemispheres to achieve a more accurate extraction of the solar period signal. The results show that: (1) although the intensity of activity is higher in the Northern Hemisphere than in the Southern Hemisphere as a whole, the mean period scales of the Rieger-type period signal for the entire 13 active cycles of the two hemispheres are extremely similar. (2) There is a clear asymmetry in the intensity of solar activity between the northern and southern hemispheres, but during most of the active weeks, the period of maximum solar activity is also the period of weakest asymmetry between the northern and southern hemispheres. (3) There is no clear correlation between the intensity of solar activity and the mean period of the solar Rieger-type period signal, and it does not follow that the higher the intensity of activity, the smaller the mean period of the Rieger-type period signal in the corresponding hemisphere, and the lower the intensity of activity, the larger the mean period of the Rieger-type period signal in the corresponding hemisphere. (4) The Rieger-type period usually occurs near the maximum period of solar activity, but in some cycles the Rieger-type period shows multiple fluctuations and can also occur during periods of rising or falling solar activity.