The Sun's meridional circulation and interior magnetic field

Abstract

To date, no self-consistent numerical simulation of the solar interior has succeeded in reproducing the observed thinness of the solar tachocline, and the persistence of uniform rotation beneath it. Although it is known that the uniform rotation can be explained by the presence of a global-scale confined magnetic field, numerical simulations have thus far failed to produce any solution where such a field remains confined against outward diffusion. We argue that the problem lies in the choice of parameters for which these numerical simulations have been performed. We construct a simple analytical magneto-hydrodynamic model of the solar interior and identify several distinct parameter regimes. For realistic solar parameter values, our results are in broad agreement with the tachocline model of Gough & McIntyre. In this regime, meridional flows driven at the base of the convection zone are of sufficient amplitude to hold back the interior magnetic field against diffusion. For the parameter values used in existing numerical simulations, on the other hand, we find that meridional flows are significantly weaker and, we argue, unable to confine the interior field. We propose a method for selecting parameter values in future numerical models.

49 pages, 11 figures, in press in the Astrophysical Journal

References in corpus (8)

• Local Helioseismology: Three Dimensional Imaging of the Solar Interior
• Magnetic confinement of the solar tachocline
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• On the Penetration of Meridional Circulation below the Solar Convection Zone II: Models with Convection Zone, the Taylor-Proudman constraint and Applications to Other Stars
• On the Interaction of Internal Gravity Waves with Magnetic Field II. Convective Forcing
• Gyroscopic pumping of large-scale flows in stellar interiors, and application to Lithium Dip stars
• Polar confinement of the Sun's interior magnetic field by laminar magnetostrophic flow

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• Dynamics of the solar tachocline III: Numerical solutions of the Gough and McIntyre model
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• Magnetic confinement of the solar tachocline: The oblique dipole
• Spin-down dynamics of magnetized solar-type stars
• A self-consistent model of the solar tachocline
• Meridional Circulation Dynamics in a Cyclic Convective Dynamo
• On the dynamics of overshooting convection in spherical shells: Effect of density stratification and rotation
• On the dynamical interaction between overshooting convection and an underlying dipole magnetic field -- I. The non-dynamo regime