From fibril to diffuse fields during dynamo saturation

TL;DR

This paper investigates how magnetic fields in a large-scale dynamo become more diffuse and less intermittent during saturation, using simulations that highlight the roles of turbulence, shear, and magnetic buoyancy.

Contribution

It demonstrates through simulations that dynamo saturation leads to a more diffuse, non-intermittent magnetic field, emphasizing the importance of downward pumping and near-surface shear in solar dynamo models.

Findings

Magnetic fields become more diffuse during dynamo saturation.

Downward pumping effects dominate over magnetic buoyancy.

Distributed dynamo operation in the Sun's near-surface shear layer is supported.

Abstract

The degree of intermittency of the magnetic field of a large-scale dynamo is considered. Based on simulations it is argued that there is a tendency for the field to become more diffuse and non-intermittent as the dynamo saturates. The simulations are idealized in that the turbulence is strongly helical and shear is strong, so the tendency for the field to become more diffuse is somewhat exaggerated. Earlier results concerning the effects of magnetic buoyancy are discussed. It is emphasized that the resulting magnetic buoyancy is weak compared with the stronger effects of simultaneous downward pumping. These findings are used to support the notion that the solar dynamo might operate in a distributed fashion where the near-surface shear layer could play an important role.