The mean-field solar dynamo with double cell meridional circulation pattern

TL;DR

This paper presents a mean-field solar dynamo model incorporating double-cell meridional circulation, realistic solar rotation, and turbulent effects, successfully reproducing observed solar magnetic cycle features and sunspot-polar field synchronization.

Contribution

It introduces a robust dynamo model with double-cell circulation that aligns well with solar observations, extending previous flux-transport models.

Findings

The model reproduces solar magnetic cycle properties across various parameters.

Optimal agreement with observations occurs at a surface meridional flow speed of about 12 m/s.

The model captures the synchronization between sunspot activity and polar magnetic fields.

Abstract

Recent findings of helioseismology as well as advances in direct numerical simulations of global dynamics of the Sun have indicated that in each solar hemisphere the meridional circulation forms the two cells along the in the convection zone. We investigate properties of a mean-field solar dynamo with such double-cell meridional circulation. The dynamo model also includes the realistic profile of solar differential rotation (including the tachocline and subsurface shear layer), and takes into account effects of turbulent pumping, anisotropic turbulent diffusivity, and conservation of magnetic helicity. Contrary to previous flux-transport dynamo models, it is found that the dynamo model can robustly reproduce the basic properties of the solar magnetic cycles for a wide range of model parameters and the circulation speed. The best agreement with observations is achieved when the surface speed of meridional circulation is about 12 m/s. For this circulation speed the simulated sunspot activity shows good synchronization with the polar magnetic fields. Such synchronization was indeed observed during the past sunspot cycles 21 and 22. We compare theoretical and observed phase diagrams of the sunspot number and the polar field strength and discuss the peculiar properties of Cycle 23.