Solar Magnetic Fields

TL;DR

This review summarizes observational and theoretical insights into the Sun's magnetic field, including the solar cycle, dynamo mechanisms, and magnetic phenomena, highlighting recent high-resolution observations and modeling efforts.

Contribution

It provides a comprehensive overview of the generation, evolution, and impact of solar magnetic fields, integrating recent observational data with theoretical models.

Findings

The solar cycle supports a large-scale dynamo model.

Coronal magnetic field variations can be accurately modeled.

Small-scale magnetic fields evolve continually, indicating small-scale dynamo action.

Abstract

This review provides an introduction to the generation and evolution of the Sun's magnetic field, summarising both observational evidence and theoretical models. The eleven year solar cycle, which is well known from a variety of observed quantities, strongly supports the idea of a large-scale solar dynamo. Current theoretical ideas on the location and mechanism of this dynamo are presented. The solar cycle influences the behaviour of the global coronal magnetic field and it is the eruptions of this field that can impact on the Earth's environment. These global coronal variations can be modelled to a surprising degree of accuracy. Recent high resolution observations of the Sun's magnetic field in quiet regions, away from sunspots, show that there is a continual evolution of a small-scale magnetic field, presumably produced by small-scale dynamo action in the solar interior. Sunspots, a natural consequence of the large-scale dynamo, emerge, evolve and disperse over a period of several days. Numerical simulations can help to determine the physical processes governing the emergence of sunspots. We discuss the interaction of these emerging fields with the pre-existing coronal field, resulting in a variety of dynamic phenomena.