Understanding mechanisms underlying solar cycle predictability with a general framework

TL;DR

This paper develops a general framework linking surface magnetic fields to solar dynamo predictability, emphasizing the role of flux-transport processes and the surface poloidal field in different dynamo models.

Contribution

It introduces a quantitative criterion for dynamo predictability based on surface magnetic field coupling, applicable to various dynamo models including Babcock-Leighton and mean-field types.

Findings

Surface magnetic field predictability depends on flux-transport coupling.

The surface poloidal field must represent the interior poloidal field for predictability.

Net toroidal flux serves as a proxy for interior toroidal field.

Abstract

The large-scale magnetic field observed at the solar surface is produced by the interior dynamo process. Whether this surface field also provides the dominant seed for the subsequent dynamo cycle, however, remains controversial, with important consequences for the predictive skill of solar dynamo models.We investigate the physical conditions under which this predictive skill of the surface field arises in dynamo models within a general framework.By applying Stokes' theorem to the magnetic induction equation, we establish a direct physical link between the surface magnetic field and the subsequent dynamo process. The dominance of the surface induction integral in the net toroidal flux generation rate provides a quantitative criterion for assessing dynamo predictability, which we apply to five representative dynamo models.This general framework shows that the surface magnetic field acquires predictive power when the surface poloidal field is efficiently coupled back into the dynamo loop through flux-transport processes (e.g., meridional circulation), a condition that can be satisfied in both Babcock-Leighton (BL)-type and $\alpha-\Omega$ mean-field dynamo models. The framework further identifies a new condition under which the surface magnetic field acquires predictive power: namely, that it represents the radial component of the interior poloidal field, as in the original BL-type dynamo scenario. In addition, the non-zero net toroidal flux across different dynamo models supports its use as a proxy linking the interior toroidal field to surface flux emergence.