The asymmetry of sunspot cycles and Waldmeier relations as due to nonlinear surface-shear shaped dynamo

TL;DR

This paper investigates a nonlinear solar dynamo model influenced by surface shear and turbulent parameters, explaining sunspot cycle asymmetries and Waldmeier relations through magnetic helicity feedback.

Contribution

It introduces a mean-field dynamo model incorporating magnetic helicity evolution and nonlinear feedback, explaining key solar cycle features.

Findings

Model qualitatively reproduces sunspot cycle asymmetries.

Explains Waldmeier effects through nonlinear dynamo processes.

Highlights importance of surface shear in solar cycle dynamics.

Abstract

The paper presents a study of a solar dynamo model operating in the bulk of the convection zone with the toroidal magnetic field flux concentrated in the subsurface rotational shear layer. We explore how this type of dynamo may depend on spatial variations of turbulent parameters and on the differential rotation near the surface. The mean-field dynamo model takes into account the evolution of magnetic helicity and describes its nonlinear feedback on the generation of large-scale magnetic field by the $\alpha$-effect. We compare the magnetic cycle characteristics predicted by the model, including the cycle asymmetry (associated with the growth and decay times) and the duration - amplitude relation (Waldmeier's effects), with the observed sunspot cycle properties. We show that the model qualitatively reproduces the basic properties of the solar cycles.