Shape of solar cycles and mid-term solar activity oscillations

TL;DR

This paper investigates the 5-6 year mid-term oscillations in solar activity, linking them to nonlinear dynamo processes and cycle shape, providing a physical explanation for these intermediate-scale variations.

Contribution

It demonstrates that mid-term solar oscillations originate from nonlinearities and non-harmonic cycle shapes in the solar dynamo model, offering a physical basis for these phenomena.

Findings

Mid-term oscillations are linked to dynamo nonlinearities.

These oscillations are related to the non-harmonic shape of solar cycles.

The study provides a physical explanation for intermediate solar activity variations.

Abstract

The evolution of the solar activity comprises, apart from the well-known 11-year cycle, various temporal scales ranging from months up to the secondary cycles known as mid-term oscillations. Its nature deserves a physical explanation. In this work, we consider the 5-to-6 year oscillations as derived both from sunspot and from solar magnetic dipole time series. Using the solar dynamo model, we deduced that these variations may be a manifestation of the dynamo nonlinearities and non-harmonic shape of the solar activity cycles. We conclude that the observed mid-term oscillations are related to the nonlinear saturation of the dynamo processes in the solar interior.