C.D.S. - SIMBAD4 rel 1.7 - 2020.09.30CEST12:35:35

2015A&A...573A..80R - Astronomy and Astrophysics, volume 573A, 80-80 (2015/1-1)

The angular momentum transport by unstable toroidal magnetic fields.


Abstract (from CDS):

We demonstrate with a nonlinear magnetohydrodynamic (MHD) code that angular momentum can be transported because of the magnetic instability of toroidal fields under the influence of differential rotation, and that the resulting effective viscosity may be high enough to explain the almost rigid-body rotation observed in radiative stellar cores. We only consider stationary, current-free fields, and only those combinations of rotation rates and magnetic field amplitudes which provide maximal numerical values of the viscosity. We find that the dimensionless ratio of the effective over molecular viscosity, νT/ν, linearly grows with the Reynolds number of the rotating fluid multiplied by the square-root of the magnetic Prandtl number, which is approximately unity for the considered red subgiant star KIC 7341231. For the interval of magnetic Reynolds numbers considered - which is restricted by numerical constraints of the nonlinear MHD code - the magnetic Prandtl number has a remarkable influence on the relative importance of the contributions of the Reynolds stress and the Maxwell stress to the total viscosity, which is magnetically dominated only for Pm>0.5. We also find that the magnetized plasma behaves as a non-Newtonian fluid, i.e., the resulting effective viscosity depends on the shear in the rotation law. The decay time of the differential rotation thus depends on its shear and becomes longer and longer during the spin-down of a stellar core.

Abstract Copyright:

Journal keyword(s): instabilities - magnetic fields - diffusion - turbulence - magnetohydrodynamics (MHD)

Simbad objects: 2

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Number of rows : 2

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 BD+42 3187 RG* 18 54 16.9545538305 +42 59 00.382313454       9.6   G2 69 0
2 KIC 8366239 RG* 19 28 19.0902589679 +44 19 18.594810144   13.35 11.71     G6V 39 0

    Equat.    Gal    SGal    Ecl

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