The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses

Martin Elias Pessah; Chi-kwan Chan; Dimitrios Psaltis

doi:10.1111/j.1365-2966.2007.12574.x

The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses

Martin Elias Pessah, Chi-kwan Chan, Dimitrios Psaltis

Niels Bohr International Academy

33 Citations (Scopus)

Abstract

Numerical simulations of turbulent, magnetized, differentially rotating flows driven by the magnetorotational instability are often used to calculate the effective values of alpha viscosity that is invoked in analytical models of accretion discs. In this paper we use various dynamical models of turbulent magnetohydrodynamic stresses, as well as numerical simulations of shearing boxes, to show that angular momentum transport in MRI-driven accretion discs cannot be described by the standard model for shear viscosity. In particular, we demonstrate that turbulent magnetorotational stresses are not linearly proportional to the local shear and vanish identically for angular velocity profiles that increase outwards.

Original language	English
Journal	Monthly Notices of the Royal Astronomical Society
Volume	383
Issue number	2
Pages (from-to)	683-690
Number of pages	7
ISSN	0035-8711
DOIs	https://doi.org/10.1111/j.1365-2966.2007.12574.x
Publication status	Published - 6 Dec 2006

Keywords

astro-ph

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10.1111/j.1365-2966.2007.12574.x

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abstract = "Numerical simulations of turbulent, magnetized, differentially rotating flows driven by the magnetorotational instability are often used to calculate the effective values of alpha viscosity that is invoked in analytical models of accretion discs. In this paper we use various dynamical models of turbulent magnetohydrodynamic stresses, as well as numerical simulations of shearing boxes, to show that angular momentum transport in MRI-driven accretion discs cannot be described by the standard model for shear viscosity. In particular, we demonstrate that turbulent magnetorotational stresses are not linearly proportional to the local shear and vanish identically for angular velocity profiles that increase outwards.",

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AU - Pessah, Martin Elias

AU - Chan, Chi-kwan

AU - Psaltis, Dimitrios

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Y1 - 2006/12/6

N2 - Numerical simulations of turbulent, magnetized, differentially rotating flows driven by the magnetorotational instability are often used to calculate the effective values of alpha viscosity that is invoked in analytical models of accretion discs. In this paper we use various dynamical models of turbulent magnetohydrodynamic stresses, as well as numerical simulations of shearing boxes, to show that angular momentum transport in MRI-driven accretion discs cannot be described by the standard model for shear viscosity. In particular, we demonstrate that turbulent magnetorotational stresses are not linearly proportional to the local shear and vanish identically for angular velocity profiles that increase outwards.

AB - Numerical simulations of turbulent, magnetized, differentially rotating flows driven by the magnetorotational instability are often used to calculate the effective values of alpha viscosity that is invoked in analytical models of accretion discs. In this paper we use various dynamical models of turbulent magnetohydrodynamic stresses, as well as numerical simulations of shearing boxes, to show that angular momentum transport in MRI-driven accretion discs cannot be described by the standard model for shear viscosity. In particular, we demonstrate that turbulent magnetorotational stresses are not linearly proportional to the local shear and vanish identically for angular velocity profiles that increase outwards.

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DO - 10.1111/j.1365-2966.2007.12574.x

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JO - Monthly Notices of the Royal Astronomical Society

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The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses

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