Abstract
The form of the solar meridional circulation is a very important ingredient for mean field flux transport dynamo models. Yet a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work we use results from 3D global simulations of solar convection to infer the dynamical behavior of the established meridional circulation. We make a direct comparison between the meridional circulation that arises in these simulations and the latest observations. Based on our results we argue that there should be an equatorward flow at the base of the convection zone at mid latitudes, below the current maximum depth helioseismic measures can probe (0.75 R). We also provide physical arguments to justify this behaviour. The simulations indicate that the meridional circulation undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of observation that involve long averaging periods of helioseismic data. Also noteworthy is the fact that these topological changes indicate a rich interaction between magnetic fields and plasma flows, which challenges the ubiquitous kinematic approach used in the vast majority of mean field dynamo simulations.
Highlights
The pressing need for a better understanding of space weather phenomenology and its implications has provided impetus for ongoing improvements to solar dynamo models.a fully detailed and consensual picture adequately explaining the origin and evolution of the large-scale solar magnetic field has not yet materialized
Before we investigate the dynamics of the meridional circulation (MC) in our simulations, we first assess the degree of resemblance between the simulated meridional flow and the solar MC
Based on 3D MHD global simulations of solar convection, we presented arguments that favor the existence of an equatorward flow below 0.75 R, near the base of the convection zone (CZ) at mid to high latitudes
Summary
The pressing need for a better understanding of space weather phenomenology and its implications has provided impetus for ongoing improvements to solar dynamo models. Among the several types of extant mean-field models (see review by Charbonneau 2010), a specific class of dynamo model known as meanfield Babcock–Leighton Flux Transport Dynamos (FTDs) has been successful in explaining some of the main observational features of the solar cycle (e.g., Wang et al 1991; Dikpati & Charbonneau 1999; Nandy & Choudhuri 2002; Karak et al 2014) These models rely heavily on the advective role of the meridional circulation (MC), a relatively weak, large-scale plasma flow that is thought to act as a conveyor belt in the convection zone (CZ), transporting magnetic flux in radius and latitude. These simulations reach a turbulent regime characterized by considerable dynamic range when zonal averages are used to define large scales, and fluctuations around these averages are used to define small scales (Racine et al 2011)
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