Origin and Recovery from Grand Solar Minima in a Time Delay Dynamo Model with Magnetic Noise as an Additional Poloidal Source

TL;DR

This study uses a delay differential equation dynamo model with magnetic noise to explain the occurrence, recovery, and statistical properties of grand solar minima, aligning well with observed sunspot data.

Contribution

It introduces magnetic noise as a crucial factor enabling recovery from grand minima in a Babcock-Leighton dynamo model, highlighting its role in solar cycle dynamics.

Findings

Magnetic noise allows the model to recover from grand minima.

The model exhibits bimodal energy distribution and intermittency.

Grand minima duration correlates with noise level.

Abstract

We explore a reduced Babcock-Leighton (BL) dynamo model based on delay differential equations using numerical bifurcation analysis. This model reveals hysteresis, seen in the recent mean-field dynamo model and the direct numerical simulations of turbulent dynamos. The BL model with 'magnetic noise' as an additional weak-source of the poloidal field recovers the solar cycle every time from grand minima, which BL source alone cannot do. The noise-incorporated model exhibits a bimodal distribution of toroidal field energy confirming two modes of solar activity. It also shows intermittency and reproduces phase space collapse, an experimental signature of the Maunder Minimum. The occurrence statistics of grand minima in our model agree reasonably well with the observed statistics in the reconstructed sunspot number. Finally, we demonstrate that the level of magnetic noise controls the duration of grand minima and even has a handle over its waiting period, suggesting a triggering effect of grand minima by the noise and thus shutting down the global dynamo. Therefore, we conclude that the 'magnetic noise' due to small-scale turbulent dynamo action (or other sources) plays a vital role even in Babcock-Leighton dynamo models.