Importance of Meridional Circulation in Flux Transport Dynamo: The Possibility of a Maunder-like Grand Minimum

TL;DR

This study highlights the critical role of meridional circulation in flux transport dynamo models, demonstrating its influence on solar cycle features and the potential to simulate Maunder-like minima, especially in diffusion-dominated regimes.

Contribution

It shows that variations in meridional circulation can reproduce solar cycle characteristics and grand minima, emphasizing the importance of diffusion-dominated dynamo models.

Findings

Diffusion-dominated dynamo models can replicate Maunder minima.

Slower meridional circulation weakens the dynamo by increasing diffusion time.

Advection-dominated models fail to reproduce these phenomena.

Abstract

Meridional circulation is an important ingredient in flux transport dynamo models. We have studied its importance on the period, the amplitude of the solar cycle, and also in producing Maunder-like grand minima in these models. First, we model the periods of the last 23 sunspot cycles by varying the meridional circulation speed. If the dynamo is in a diffusion-dominated regime, then we find that most of the cycle amplitudes also get modeled up to some extent when we model the periods. Next, we propose that at the beginning of the Maunder minimum the amplitude of meridional circulation dropped to a low value and then after a few years it increased again. Several independent studies also favor this assumption. With this assumption, a diffusion-dominated dynamo is able to reproduce many important features of the Maunder minimum remarkably well. If the dynamo is in a diffusion-dominated regime, then a slower meridional circulation means that the poloidal field gets more time to diffuse during its transport through the convection zone, making the dynamo weaker. This consequence helps to model both the cycle amplitudes and the Maunder-like minima. We, however, fail to reproduce these results if the dynamo is in an advection-dominated regime.