A Model of Frequency Modulation of the 11-Year Cycle of Solar Activity

Using wavelet analysis, a study was made of variations in the length of the solar cycle and their characteristic features in 1700–2020. In addition to the stable 11-year component, in the spectrum of solar activity there are three components of the Gleissberg cycle: a 115-year component is visible over the entire time interval and a 60-year component occurs until 1875. The classical branch with a period of 88 years is separated in 1775–1910s. In the wavelet spectrum, the Dalton minimum is characterized by a sharp increase in the length of the 11-year component against the background of a decrease in amplitude in 1800, and also by the fact that all three branches of the Gleissberg cycle are practically symphasic, and their amplitudes are close to the maximum. A model is constructed in which the period of the 11-year harmonic oscillation is modulated by three branches of the Gleissberg cycle. It is found that such a model of frequency modulation describes the general evolution of the spectrum and its main features well, in particular, the Dalton minimum.