Occurrence of the 1.3-year periodicity in the large-scale solar magnetic field for 8 solar cycles

The data on solar magnetic fields since 1915 have been inferred from H-alpha filament observations. We have used these data together with direct magnetographic observations to study the cycle variation of the large-scale field. Quasi-periodic oscillations with a period of 1.3 years have been detected in the Sun during 8 cycles. They are not present all the time, but are rather seen at maxima and in declining phases of some cycles. No distinct correlation is revealed with the height of the cycle and alternation of the even and odd cycles. Oscillations with a period of 1.3 years are closely associated with quasi-biennial oscillations (QBO) but, occasionally, they occur in anti-phase.