Investigating global convective dynamos with mean-field models: full spectrum of turbulent effects required

TL;DR

This study demonstrates that accurately modeling solar and stellar dynamos requires incorporating the full spectrum of turbulent effects, validated through a combination of global convective dynamo simulations and mean-field theory.

Contribution

The paper introduces a comprehensive approach combining GCD simulations and mean-field models to include all turbulent effects, challenging simplified dynamo models.

Findings

Good agreement between mean-field and simulation results when all turbulent effects are included

Inclusion of previously neglected turbulent effects is essential for accurate dynamo modeling

Simplified models may not capture the full dynamo dynamics in stars and the Sun.

Abstract

The role of turbulent effects for dynamos in the Sun and stars continues to be debated. Mean-field (MF) theory provides a broadly used framework to connect these effects to fundamental magnetohydrodynamics. While inaccessible observationally, turbulent effects can be directly studied using global convective dynamo (GCD) simulations. We measure the turbulent effects in terms of turbulent transport coefficients, based on the MF framework, from an exemplary GCD simulation using the test-field method. These coefficients are then used as an input into an MF model. We find a good agreement between the MF and GCD solutions, which validates our theoretical approach. This agreement requires all turbulent effects to be included, even those which have been regarded as unimportant so far. Our results suggest that simple dynamo models, as are commonly used in the solar and stellar community, relying on very few, precisely fine-tuned turbulent effects, may not be representative of the full dynamics of dynamos in global convective simulations and astronomical objects.