Self-consistent theory of turbulent transport in the solar tachocline II. Tachocline confinement

N. Leprovost, Eun Jin Kim

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Aims. We provide a consistent theory of the tachocline confinement (or anisotropic momentum transport) within a hydrodynamical turbulence model. The goal is to explain helioseismological data, which show that the solar tachocline thickness is at most 5% of the solar radius, despite the fact that, due to radiative spreading, this transition layer should have thickened to a much more significant value during the sun's evolution. Methods. Starting from the first principle with the physically plausible assumption that turbulence is driven externally (e.g. by plumes penetrating from the convection zone), we derive turbulent (eddy) viscosity in the radial (vertical) and azimuthal (horizontal) directions by incorporating the crucial effects of shearing due to radial and latitudinal differential rotations in the tachocline. Results. We show that the simultaneous presence of both shears effectively induces a much more efficient momentum transport in the horizontal plane than in the radial direction. In particular, in the case of strong radial turbulence (driven by overshooting plumes from the convection zone), the ratio of the radial to horizontal eddy viscosity is proportional to A-1/3, where A ( is the strength of the shear due to radial differential rotation. In comparison, in the case of horizontally driven turbulence, this ratio becomes of order -∈2, with negative radial eddy viscosity. Here, ∈ (≪ 1) is the ratio of the radial to latitudinal shear. The resulting anisotropy in momentum transport could thus be strong enough to operate as a mechanism for the tachocline confinement against spreading.

Original languageEnglish
Pages (from-to)617-621
Number of pages5
JournalAstronomy and Astrophysics
Volume456
Issue number2
DOIs
Publication statusPublished - 31 Aug 2006
Externally publishedYes

Bibliographical note

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Keywords

  • Sun: interior
  • Sun: rotation
  • Turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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