Local Three-dimensional Magnetohydrodynamic Simulations of Accretion Disks

TLDR

We have performed three‑dimensional magnetohydrodynamic simulations of an accretion disk to study the nonlinear development of the magnetorotational instability. The authors use a local shearing‑box model with tidal and Coriolis forces, periodic vertical and azimuthal boundaries, and a method‑of‑characteristics constrained‑transport algorithm, initializing with either vertical or azimuthal magnetic fields. The simulations show that the magnetorotational instability drives sustained, anisotropic turbulence that transports angular momentum outward, with magnetic stresses dominating Reynolds stresses, energy flux concentrated at the largest scales, and magnetic energy density scaling with box size and initial field strength while remaining independent of sound speed. Published in The Astrophysical Journal, February 1995, DOI: 10.1086/175311.

Abstract

view Abstract Citations (1024) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Local Three-dimensional Magnetohydrodynamic Simulations of Accretion Disks Hawley, John F. ; Gammie, Charles F. ; Balbus, Steven A. Abstract We have performed three-dimensional magnetohydrodynamic numerical simulations of an accretion disk to study the nonlinear development of the magnetorotational instability. We use a disk model that is local in the sense that it incorporates tidal and Coriolis forces but neglects background gradients in pressure and density. For simplicity we omit the vertical component of gravity and employ periodic boundary conditions in the vertical and azimuthal directions, and shearing-periodic boundary conditions in the radial direction. Our numerical method is an implementation of the "method of characteristics-constrained transport" algorithm. Most of the simulations begin with either a purely vertical or purely azimuthal magnetic field. Our major result is that turbulence is initiated and sustained by the magnetic instability. We provide a detailed characterization of the saturated turbulent state. The turbulence is anisotropic in a sense that implies an outward flux of angular momentum. The turbulent energy and angular momentum flux is dominated by magnetic stress rather than Reynolds stress. Most of the energy and angular momentum flux is concentrated at the largest scales. We find that the magnetic energy density in the saturated state is proportional to the product of the size of the simulation box and the initial field strength and is independent of the sound speed. Publication: The Astrophysical Journal Pub Date: February 1995 DOI: 10.1086/175311 Bibcode: 1995ApJ...440..742H Keywords: ACCRETION; ACCRETION DISKS; INSTABILITIES; MAGNETOHYDRODYNAMICS: MHD full text sources ADS |