5 research outputs found
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
The solar convection zone exhibits a strong level of differential rotation,
whereby the rotation period of the polar regions is about 25-30% longer than
the equatorial regions. The Coriolis force associated with these zonal flows
perpetually "pumps" the convection zone fluid, and maintains a quasi-steady
circulation, poleward near the surface. What is the influence of this
meridional circulation on the underlying radiative zone, and in particular,
does it provide a significant source of mixing between the two regions? In
Paper I, we began to study this question by assuming a fixed meridional flow
pattern in the convection zone and calculating its penetration depth into the
radiative zone. We found that the amount of mixing caused depends very
sensitively on the assumed flow structure near the radiative--convective
interface. We continue this study here by including a simple model for the
convection zone "pump", and calculating in a self-consistent manner the
meridional flows generated in the whole Sun. We find that the global
circulation timescale depends in a crucial way on two factors: the overall
stratification of the radiative zone as measured by the Rossby number times the
square root of the Prandtl number, and, for weakly stratified systems, the
presence or absence of stresses within the radiative zone capable of breaking
the Taylor-Proudman constraint. We conclude by discussing the consequences of
our findings for the solar interior and argue that a potentially important
mechanism for mixing in Main Sequence stars has so far been neglected.Comment: 42 pages, 13 figures. Submitted to Ap