The Influence of Asymmetrical Distribution of Hemispheric Sunspot Areas on Some Solar Parameters’ Periodicities during the Period 1945–2017: Wavelet Analysis
M. A. El‐Borie, A. M. El-Taher, A. A. Thabet, S. F. Ibrahim, N. S. Aly, A. A. Bishara
Abstract
Abstract Monthly data of some solar parameters (the solar radio flux F 10.7, the plage area PA, the coronal index CI, the solar mean magnetic field B , and the solar flare index SFI) during the period 1945–2017 have been classified into two groups (northern and southern) based on the distribution of the monthly averages of the hemispheric sunspot areas (SSAs). This has been done to investigate the symmetry and/or asymmetry in periodicities between the hemispheric groups for these parameters by utilizing the Morlet wavelet technique. For each of the considered parameters except B , it is observed that the most dominant and significant period (above the 95% confidence level) in both the wavelet spectra (WPS and GWS) for both hemispheric groups is the solar activity cycle at 10.7 yr during the entire time interval. The power values for other periods appeared to be quite small relative to that of the 10.7 yr period, and of less significance (below the 95% confidence level). For B , the most remarkable sign is the disappearance of the prominent peak of the solar activity cycle. The Hale cycle is clearly seen in both hemispheric groups of B , with a slight shift in time between the two hemispheric groups, and it increased through the entire considered duration. Periodicities of 10.7, 3.5, 1.5, and 0.8 yr have been observed in the northern hemispheric group of the parameters SSAs, F 10.7, PA, CI, and SFI, indicating a possible correlation between them. For the southern hemispheric group, however, periodicities of 10.7, 5.4, and 0.8 yr have been revealed for the parameters F 10.7, PA, and CI.