Helioseismic data inclusion in solar dynamo models

TL;DR

This paper develops methods to incorporate helioseismic observational data into solar dynamo models, enhancing their realism and understanding of the solar magnetic cycle.

Contribution

It introduces data assimilation techniques for differential rotation and meridional circulation profiles based on helioseismic constraints in solar dynamo simulations.

Findings

Latitudinal shear in the convection zone significantly influences toroidal field generation.

The meridional flow speed at the convection zone base primarily affects the dynamo cycle period.

Assimilated data produce different dynamo behaviors compared to traditional analytic profiles.

Abstract

An essential ingredient in kinematic dynamo models is the velocity field within the solar convection zone. In particular, the differential rotation is now well constrained by helioseismic observations. Helioseismology also gives us information about the depth-dependence of the meridional circulation in the near-surface layers. The typical velocity inputs used in solar dynamo models, however, continue to be an analytic fit to the observed differential rotation and a theoretically constructed meridional flow profile that matches only the peak flow speed at the surface. Here we take the first steps towards realistic helioseismic data assimilation, by presenting methodologies for constructing differential rotation and meridional circulation profiles that more closely conform to the observational constraints currently available. We also present simulations driven by the assimilated rotation and four plausible profiles for the internal meridional circulation -- all of which match the helioseismically inferred near-surface depth-dependence, but whose magnitudes are made to vary. We discuss how the results compare with those that are driven by purely analytic fits. Our results indicate that the latitudinal shear of the rotation in the bulk of the solar convection zone plays a more important role, than either the tachocline or surface radial shear, in the induction of toroidal field. We also find that it is the speed of the equatorward counter-flow in the meridional flow at the base of the convection zone, and not how far into the radiative interior it penetrates, that primarily determines the dynamo cycle period. Given that improved helioseismic constraints are expected to be available in the future, our analysis lays the basis for assimilating these data within dynamo models.