Long-term Periodicities in North–south Asymmetry of Solar Activity and Alignments of the Giant Planets

The existence of ≈ 12-year and ≈ 51-year periodicities in the north–south asymmetry of solar activity is well known. However, the origin of these as well as the well-known relatively short periodicities in the north–south asymmetry is not yet clear. Here we have analyzed the combined daily data of sunspot groups reported in Greenwich Photoheliographic Results (GPR) and Debrecen Photoheliographic Data (DPD) during the period 1874 – 2017 and the data of the orbital positions (ecliptic longitudes) of the giant planets in ten-day intervals during the period 1600 – 2099. Our analysis suggests that ≈ 12-year and ≈ 51-year periodicities in the north–south asymmetry of solar activity are the manifestations of the differences in the strengths of ≈ 11-year and ≈ 51-year periodicities of activity in the northern- and southern-hemispheres. During the period 1874 – 2017 the Morlet wavelet power spectrum of the north–south asymmetry of sunspot-group area and that of the mean absolute difference ($\overline{\psi _{\mathrm{D}}}$) of the orbital positions of the giant planets are found to be similar. Particularly, there is a suggestion that the ≈ 12-year and ≈ 51-year periodicities in the north–south asymmetry of sunspot-group area occurred during approximately the same times as the corresponding periodicities in $\overline{\psi _{\mathrm{D}}}$. Therefore, we suggest that there could be influence of some specific configurations of the giant planets in the origin of the ≈ 12-year and ≈ 50-year periodicities of the north–south asymmetry of solar activity.