Nature of grand minima and maxima from fully non-linear Flux-Transport Dynamos

TL;DR

This study uses a sophisticated non-linear dynamo model to analyze the occurrence and characteristics of grand solar minima and maxima, revealing their mostly memoryless nature and associated flow variations.

Contribution

It introduces a fully non-linear flux-transport dynamo model with stochastic fluctuations to study grand solar activity periods, highlighting their statistical and flow-related properties.

Findings

Grand minima and maxima are mostly governed by memoryless processes.

Meridional circulation is slower during grand maxima and faster during grand minima.

Radial differential rotation is larger during grand maxima and smaller during grand minima.

Abstract

We aim to investigate the nature and occurrence characteristics of grand solar minimum and maximum periods, which are observed in the solar proxy records such as 10Be and 14C, using a fully non-linear Babcock-Leighton type flux-transport dynamo including momentum and entropy equations. The differential rotation and meridional circulation are generated from the effect of turbulent Reynolds stress and are subjected to back-reaction from the magnetic field. To generate grand minimum and maximum-like periods in our simulations, we used random fluctuations in the angular momentum transport process, namely the Lambda-mechanism, and in the Babcock-Leighton mechanism. To characterise the nature and occurrences of the identified grand minima and maxima in our simulations, we used the waiting time distribution analyses, which reflects whether the underlying distribution arises from a random or a memory-bearing process. The results show that, in majority of the cases, the distributions of grand minima and maxima reveal that the nature of these events originates from memoryless processes. We also found that in our simulations the meridional circulation speed tends to be smaller during grand maximum, while it is faster during grand minimum periods. The radial differential rotation tend to be larger during grand maxima, while it is smaller during grand minima. The latitudinal differential rotation on the other hand is found to be larger during grand minima.