GYROSCOPIC PUMPING IN THE SOLAR NEAR-SURFACE SHEAR LAYER

Journal Article · Sat Dec 10 04:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/743/1/79· OSTI ID:22004493

Miesch, Mark S ^[1]

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1. High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307-3000 (United States)

We use global and local helioseismic inversions to explore the prevailing dynamical balances in the solar near-surface shear layer (NSSL). The differential rotation and meridional circulation are intimately linked, with a common origin in the turbulent stresses of the upper solar convection zone. The existence and structure of the NSSL cannot be attributed solely to the conservation of angular momentum by solar surface convection, as is often supposed. Rather, the turbulent angular momentum transport accounts for the poleward meridional flow while the often overlooked meridional force balance is required to maintain the mid-latitude rotational shear. We suggest that the base of the NSSL is marked by a transition from baroclinic to turbulent stresses in the meridional plane which suppress Coriolis-induced circulations that would otherwise establish a cylindrical rotation profile. The turbulent angular momentum transport must be nondiffusive and directed radially inward. Inferred mean flows are consistent with the idea that turbulent convection tends to mix angular momentum but only if the mixing efficiency is inhomogeneous and/or anisotropic. The latitudinal and longitudinal components of the estimated turbulent transport are comparable in amplitude and about an order of magnitude larger than the vertical component. We estimate that it requires 2%-4% of the solar luminosity to maintain the solar NSSL against the inertia of the mean flow. Most of this energy is associated with the turbulent transport of angular momentum out of the layer, with a spin-down timescale of {approx}600 days. We also address implications of these results for numerical modeling of the NSSL.

• OSTI ID: 22004493
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 743; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANISOTROPY
ASTROPHYSICS
CONVECTION
LUMINOSITY
MOMENT OF INERTIA
ROTATION
SEISMOLOGY
SUN