LOW-FREQUENCY ANALYSIS OF THE SUNSPOT CYCLES

The low-frequency components of the solar cycles were analysed to understand the complex amplitude modulation of the cycles. The antisymmetrical sideband distribution around the fundamental frequency (the Hale frequency) supports the idea that there are frequencies which beat the fundamental frequency. All the results were based on a linear relationship between the modulated wave and the relative sunspot numbers, but the sharpness of the cycles and the appearance of a third harmonic in the spectra shows a lack of strict proportionality between these two quantities.