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Analytical theory of tachocline transport at mid latitudes
Author(s) -
Leprovost N.,
Kim E.J.
Publication year - 2007
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200710860
Subject(s) - tachocline , physics , differential rotation , magnetohydrodynamics , magnetic diffusivity , angular momentum , magnetic field , dynamo theory , rossby radius of deformation , rossby wave , solar wind , solar rotation , dynamo , astrophysics , computational physics , classical mechanics , atmospheric sciences , quantum mechanics
Abstract We provide a theory of magnetic diffusion, momentum transport, and mixing in the solar tachocline by considering magnetohydrodynamics (MHD) turbulence on a β plane subject to a large scale shear (provided by the latitudinal differential rotation). In the strong magnetic field regime, we find that the turbulent viscosity and diffusivity are reduced by magnetic fields only, similarly to the two‐dimensional MHD case (without Rossby waves). In the weak magnetic field regime, we find a crossover scale ( L R ) from a Alfvén dominated regime (on small scales) to a Rossby dominated regime (on large scales). For parameter values typical of the tachocline, L R is larger than the solar radius so that Rossby waves are unlikely to play an important role in the transport of magnetic field and angular momentum. This is mainly due to the enhancement of magnetic back‐reaction by shearing which efficiently generates small scales, thus strong currents. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)