On global solar dynamo simulations

TL;DR

This paper reviews the current state of global solar dynamo simulations, highlighting challenges in resolution and rotation modeling, and discusses insights from local and mean-field theories to improve understanding of solar magnetic field generation.

Contribution

It provides a comprehensive review of global solar dynamo simulations, analyzing their limitations and proposing potential solutions based on lessons from local and mean-field models.

Findings

Global simulations face resolution and scale separation challenges.

Reproducing solar internal rotation remains difficult.

Insights from local and mean-field theories can inform improvements.

Abstract

Global dynamo simulations solving the equations of magnetohydrodynamics (MHD) have been a tool of astrophysicists who try to understand the magnetism of the Sun for several decades now. During recent years many fundamental issues in dynamo theory have been studied in detail by means of local numerical simulations that simplify the problem and allow the study of physical effects in isolation. Global simulations, however, continue to suffer from the age-old problem of too low spatial resolution, leading to much lower Reynolds numbers and scale separation than in the Sun. Reproducing the internal rotation of the Sun, which plays a crucual role in the dynamo process, has also turned out to be a very difficult problem. In the present paper the current status of global dynamo simulations of the Sun is reviewed. Emphasis is put on efforts to understand how the large-scale magnetic fields, i.e. whose length scale is greater than the scale of turbulence, are generated in the Sun. Some lessons from mean-field theory and local simulations are reviewed and their possible implications to the global models are discussed. Possible remedies to some current issues of solar simulations are put forward.