Wavelet-analysis of series of observations of relative sunspot numbers. The dependence of the periods of cyclic activity on the time at different time scales

TL;DR

This paper uses wavelet analysis to study sunspot numbers, revealing multiple overlapping activity cycles with varying periods from two years to a century, which change gradually over time.

Contribution

It introduces a continuous wavelet-transform method to analyze the temporal evolution of solar activity cycles in sunspot data.

Findings

Multiple activity cycles coexist at any given time.

Cycle periods vary from quasi biennial to centennial.

Periodic variations in solar activity gradually change over time.

Abstract

We applied the method of continuous wavelet-transform to high-quality time-frequency analysis to the sets of observations of relative sunspot numbers. Wavelet analysis of these data reveals the following pattern: at the same time there are several activity cycles whose periods vary widely from the quasi biennial up to the centennial period. These relatively low-frequency periodic variations of the solar activity gradually change the values of periods of different cycles in time. This phenomenon can be observed in every cycle of activity.