The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses

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