TESTING CONVERGENCE FOR GLOBAL ACCRETION DISKS

Global disk simulations provide a powerful tool for investigating accretion and the underlying magnetohydrodynamic turbulence driven by magneto-rotational instability (MRI). We use the flux-conservative Athena code to conduct a series of experiments on disks having a variety of magnetic topologies t...

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Published inThe Astrophysical journal Vol. 772; no. 2; pp. 1 - 17
Main Authors Hawley, John F, Richers, Sherwood A, Guan, Xiaoyue, Krolik, Julian H
Format Journal Article
LanguageEnglish
Published United States 01.08.2013
Subjects
ACCRETION DISKS
ALGORITHMS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BLACK HOLES
Brackets
BRIGHTNESS
CONVERGENCE
Flux
Initial conditions
Instability
INTERPOLATION
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
SIMULATION
Solvers
SYMMETRY
TURBULENCE
WAVELENGTHS
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Summary:Global disk simulations provide a powerful tool for investigating accretion and the underlying magnetohydrodynamic turbulence driven by magneto-rotational instability (MRI). We use the flux-conservative Athena code to conduct a series of experiments on disks having a variety of magnetic topologies to determine what constitutes adequate resolution. We develop and apply several resolution metrics: [left angle bracket]Q sub(z)[right angle bracket] and [left angle bracket]Q sub([phi])[right angle bracket], the ratio of the grid zone size to the characteristic MRI wavelength, alpha sub(mag), the ratio of the Maxwell stress to the magnetic pressure, and [left angle bracket]B super(2)R[right angle bracket]/[left angle bracket]B super(2)[phi][right angle bracket], the ratio of radial to toroidal magnetic field energy. For the initial conditions considered here, adequate resolution is characterized by [left angle bracket]Q sub(z)[right angle bracket] [> or =, slanted] 15, [left angle bracket]Q sub([phi])[right angle bracket] [> or =, slanted] 20, alpha sub(mag) approximately 0.45, and [left angle bracket]B super(2)R[right angle bracket]/[left angle bracket]B super(2)[phi][right angle bracket] approximately 0.2. Use of the Harten-Lax-van Leer-Einfeldt flux solver or second-order interpolation can significantly degrade the effective resolution compared to the Harten-Lax-van Leer discontinuities flux solver and third-order interpolation.
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ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/772/2/102