Query : 2016A&A...588A.147P

2016A&A...588A.147P - Astronomy and Astrophysics, volume 588A, 147-147 (2016/4-1)

Mixing of a passive scalar by the instability of a differentially rotating axial pinch.


Abstract (from CDS):

The mean-field diffusion of passive scalars such as lithium, beryllium or temperature dispersals due to the magnetic Tayler instability of a rotating axial pinch is considered. Our study is carried out within a Taylor-Couette setup for two rotation laws: solid-body quasi-Kepler rotation. The minimum magnetic Prandtl number used is 0.05, and the molecular Schmidt number Sc of the fluid varies between 0.1 and 2. An effective diffusivity coefficient for the mixing is numerically measured by the decay of a prescribed concentration peak located between both cylinder walls. We find that only models with Sc exceeding 0.1 basically provide finite instability-induced diffusivity values. We also find that for quasi-Kepler rotation at a magnetic Mach number Mm≃2, the flow transits from the slow-rotation regime to the fast-rotation regime that is dominated by the Taylor-Proudman theorem. For fixed Reynolds number, the relation between the normalized turbulent diffusivity and the Schmidt number of the fluid is always linear so that also a linear relation between the instability-induced diffusivity and the molecular viscosity results, just in the sense proposed by Schatzman (1977A&A....56..211S). The numerical value of the coefficient in this relation reaches a maximum at Mm≃2 and decreases for larger Mm, implying that only toroidal magnetic fields on the order of 1kG can exist in the solar tachocline.

Abstract Copyright: © ESO, 2016

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 - 2023
1 BD+42 3187 RG* 18 54 16.9544655840 +42 59 00.384912816   10.495 9.939 10.086   G2 84 0
2 TYC 3146-611-1 RG* 19 28 19.0903164432 +44 19 18.595247268   13.35 11.71     G6V 51 0

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