The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses

TY - JOUR

T1 - The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses

AU - Pessah, Martin Elias

AU - Chan, Chi-kwan

AU - Psaltis, Dimitrios

PY - 2006/12/6

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.

KW - astro-ph

U2 - 10.1111/j.1365-2966.2007.12574.x

DO - 10.1111/j.1365-2966.2007.12574.x

M3 - Journal article

SN - 0035-8711

VL - 383

SP - 683

EP - 690

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

IS - 2

ER -