Surface Flux Transport on the Sun

TL;DR

This paper reviews the surface flux transport model for solar magnetic flux evolution, focusing on recent advances in understanding transport parameters, source terms, and extensions beyond the classical steady-state assumptions.

Contribution

It provides a comprehensive overview of recent developments in the surface flux transport model, emphasizing the roles of transport parameters and source terms in solar magnetic field evolution.

Findings

Enhanced understanding of transport parameter roles

Insights into source term influences

Discussion of model extensions beyond classical assumptions

Abstract

We review the surface flux transport model for the evolution of magnetic flux patterns on the Sun's surface. Our underlying motivation is to understand the model's prediction of the polar field (or axial dipole) strength at the end of the solar cycle. The main focus is on the "classical" model: namely, steady axisymmetric profiles for differential rotation and meridional flow, and uniform supergranular diffusion. Nevertheless, the review concentrates on recent advances, notably in understanding the roles of transport parameters and - in particular - the source term. We also discuss the physical justification for the surface flux transport model, along with efforts to incorporate radial diffusion, and conclude by summarizing the main directions where researchers have moved beyond the classical model.