Modelling the occurrence of grand minima in sun-like stars using a dynamo model

TL;DR

This study uses kinematic dynamo models to analyze how the occurrence and variability of grand minima in sun-like stars depend on rotation rate and convection zone depth, revealing that slower rotation increases grand minima frequency.

Contribution

It introduces a dynamo model incorporating stochastic fluctuations and hydrodynamic flow specifications to explain grand minima occurrence in stars with different rotation rates.

Findings

Slower rotating stars have more frequent grand minima.

Rapidly rotating stars produce irregular cycles with few grand minima.

Grand minima frequency increases as stellar rotation slows.

Abstract

In this work, we have studied the variability and frequency of occurrence of the grand minima using kinematic dynamo models of one solar mass star with different rotation rates and depths of convection zones. We specify the large-scale flows (differential rotations and meridional circulations) from corresponding hydrodynamic models. We include stochastic fluctuations in the Babcock-Leighton source for the poloidal field to produce variable stellar cycles. We observe that the rapidly rotating stars produce highly irregular cycles with strong magnetic fields and rarely produce Maunder-like grand minima, whereas the slowly rotating stars (Sun and longer rotation period) produce smooth cycles of weaker strength and occasional grand minima. In general, the number of the grand minima increases with the decrease in rotation rate. These results can be explained by the fact that with the increase of rotation period, the supercriticality of the dynamo decreases, and the dynamo is more prone to produce extended grand minima in this regime.