Eddy viscosity and turbulent Schmidt number by kink-type instability of strong toroidal magnetic fields - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




Eddy viscosity and turbulent Schmidt number by kink-type instability of strong toroidal magnetic fields - Astrophysics > Solar and Stellar Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: The potential of the nonaxisymmetric magnetic instability to transportangular momentum and to mix chemicals is probed considering the stability of anearly uniform toroidal field between conducting cylinders with differentrotation rates.
The fluid between the cylinders is assumed as incompressibleand to be of uniform density.
With a linear theory the neutral-stability mapsfor m=1 are computed.
Rigid rotation must be subAlfvenic to allow instabilitywhile for differential rotation with negative shear also an unstable domainwith superAlfvenic rotation exists.
The rotational quenching of the magneticinstability is strongest for magnetic Prandtl number Pm=1 and becomes muchweaker for Pm unequal 1.
The effective angular momentum transport by theinstability is directed outwardsinwards for subrotationsuperrotation.
Theresulting magnetic-induced eddy viscosities exceed the microscopic values byfactors of 10-100.
This is only true for superAlfvenic flows; in thestrong-field limit the values remain much smaller.
The same instability alsoquenches concentration gradients of chemicals by its nonmagnetic fluctuations.The corresponding diffusion coefficient remains always smaller than themagnetic-generated eddy viscosity.
A Schmidt number of order 30 is found as theratio of the effective viscosity and the diffusion coefficient.
The magneticinstability transports much more angular momentum than that it mixes chemicals.



Autor: G.
Ruediger, M.
Gellert, M.
Schultz


Fuente: https://arxiv.org/



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