Long-term Nonlinear Behaviour of the Magnetorotational Instability in a Localised Model of an Accretion Disc
arXiv:0712.4343 · doi:10.1111/j.1365-2966.2008.12906.x
Abstract
For more than a decade, the so-called shearing box model has been used to study the fundamental local dynamics of accretion discs. This approach has proved to be very useful because it allows high resolution and long term studies to be carried out, studies that would not be possible for a global disc. Localised disc studies have largely focused on examining the rate of enhanced transport of angular momentum, essentially a sum of the Reynolds and Maxwell stresses. The dominant radial-azimuthal component of this stress tensor is, in the classic Shakura-Sunayaev model, expressed as a constant alpha times the pressure. Previous studies have estimated alpha based on a modest number of orbital times. Here we use much longer baselines, and perform a cumulative average for alpha. Great care must be exercised when trying to extract numerical alpha values from simulations: dissipation scales, computational box aspect ratio, and even numerical algorithms all affect the result. This study suggests that estimating alpha becomes more, not less, difficult as computational power increases.
10 pages, 10 figures, 2 tables, accepted by MNRAS
References in corpus (4)
- MHD simulations of the magnetorotational instability in a shearing box with zero net flux. II. The effect of transport coefficients
- Impact of dimensionless numbers on the efficiency of MRI-induced turbulent transport
- MHD simulations of the magnetorotational instability in a shearing box with zero net flux. I. The issue of convergence
- Angular Momentum Transport in Accretion Disks: Scaling Laws in MRI-driven Turbulence