ON THE PERSISTENCE OF THE 22-Y SOLAR-CYCLE

We briefly discuss the existence of precise periodicities of the Hale cycle (∼-22 y), the Gleissberg cycle (∼-88 y), and ∼-132 y cycle, in various direct and indirect indicators (as aurorae, 14C from tree rings and 10Be from polar ice) of solar activity. We consider also the behaviour of the 11y cycle and its first harmonic in modern sunspot series. It appears that the frequencies of ∼-1 c/88 y and ∼-1 c/132 y might be two subharmonics of the Hale cycle. The results support the hypothesis that the Sun behaves as a nonlinear system forced by an oscillator having the Hale frequency. The forcing element inside the Sun can be identified with a magnetofluid torsional oscillator. © 1990 Kluwer Academic Publishers.