Related papers: Angular Momentum Transport in Simulations of Accre…
The status of our current understanding of angular momentum transport in accretion disks is reviewed. The last decade has seen a dramatic increase both in the recognition of key physical processes and in our ability to carry through direct…
We examine the angular momentum transport properties of disks composed of macroscopic particles whose velocity dispersions are externally enhanced (``stirred''). Our simple Boltzmann equation model serves as an analogy for unmagnetized…
The nature of angular momentum transport in the boundary layers of accretion disks has been one of the central and long-standing issues of accretion disk theory. In this work we demonstrate that acoustic waves excited by supersonic shear in…
We perform global unstratified 3D magnetohydrodynamic simulations of an astrophysical boundary layer (BL) -- an interface region between an accretion disk and a weakly magnetized accreting object such as a white dwarf -- with the goal of…
We review mechanisms for the transport of angular momentum in accretion disks that are low mass, in the sense that the gravitational forces produced by the material in these disks has a negligible effect on disk dynamics. There is no…
Angular momentum transport in protostellar discs can take place either radially, through turbulence induced by the magnetorotational instability (MRI), or vertically, through the torque exerted by a large-scale magnetic field that threads…
The physical modeling of the accretion disk boundary layer, the region where the disk meets the surface of the accreting star, usually relies on the assumption that angular momentum transport is opposite to the radial angular frequency…
The mechanism of angular momentum transport in accretion discs has long been debated. Although the magnetorotational instability appears to be a promising process, poorly ionized regions of accretion discs may not undergo this instability.…
We perform controlled N-Body/SPH simulations of disk galaxy formation by cooling a rotating gaseous mass distribution inside equilibrium cuspy spherical and triaxial dark matter halos. We systematically study the angular momentum transport…
We report a laboratory study of the transport of angular momentum by a turbulent flow of an electrically conducting fluid confined in a thin disk. When the electromagnetic force applied to the liquid metal is large enough, the corresponding…
The radial transport of angular momentum in accretion disk is a fundamental process in the universe. It governs the dynamical evolution of accretion disks and has implications for various issues ranging from the formation of planets to the…
We present a non-linear numerical model for a geometrically thin accretion disk with the addition of stochastic non-linear fluctuations in the viscous parameter. These numerical realizations attempt to study the stochastic effects on the…
The global development of magnetohydrodynamic turbulence in an accretion disk is studied within a simplified disk model that omits vertical stratification. Starting with a weak vertical seed field, a saturated state is obtained after a few…
Detailed calculations of the physical structure of accretion disk boundary layers, and thus their inferred observational properties, rely on the assumption that angular momentum transport is opposite to the radial angular frequency gradient…
Understanding the mechanism that drives accretion has been the primary challenge in accretion disk theory. Turbulence provides a natural means of dissipation and the removal of angular momentum, but firmly establishing its presence in disks…
Grid-based magnetohydrodynamic (MHD) simulations have proven invaluable for the study of astrophysical accretion disks. However, the fact that angular momentum transport in disks is mediated by MHD turbulence (with structure down to very…
We investigate the evolution of angular momentum in SPH simulations of galaxy formation, paying particular attention to artificial numerical effects. We find that a cold gas disc forming in an ambient hot gas halo receives a strong…
I review recent work on the radial transport of angular momentum in ionized, Keplerian accretion disks. Proposed mechanisms include hydrodynamic and MHD local instabilities and long range effects mediated by wave transport. The most…
In low-mass disks, turbulent torques are probably the most important way of redistributing angular momentum. Here we present the theory of turbulent accretion disks. We show the molecular viscosity is far too small to account for the…
Semi-analytic models of self-gravitating discs often approximate the angular momentum transport generated by the gravitational instability using the phenomenology of viscosity. This allows the employment of the standard viscous evolution…