The crucial role of surface magnetic fields for the solar dynamo

TL;DR

This paper demonstrates that the surface magnetic fields of the Sun, especially the polar dipolar fields, are crucial in generating the toroidal magnetic flux that drives the solar dynamo, linking surface observations to internal magnetic processes.

Contribution

It establishes a quantitative relationship between surface magnetic flux and the internal toroidal flux, highlighting the importance of surface magnetic fields in the solar dynamo mechanism.

Findings

Net toroidal magnetic flux is determined by surface magnetic flux.

Polar dipolar magnetic field peaks at activity cycle minima.

Surface magnetic field observations can predict internal magnetic flux.

Abstract

Sunspots and the plethora of other phenomena occuring in the course of the 11-year cycle of solar activity are a consequence of the emergence of magnetic flux at the solar surface. The observed orientations of bipolar sunspot groups imply that they originate from toroidal (azimuthally orientated) magnetic flux in the convective envelope of the Sun. We show that the net toroidal magnetic flux generated by differential rotation within a hemisphere of the convection zone is determined by the emerged magnetic flux at the solar surface and thus can be calculated from the observed magnetic field distribution. The main source of the toroidal flux is the roughly dipolar surface magnetic field at the polar caps, which peaks around the minima of the activity cycle.