Testing Convergence for Global Accretion Disks

Hawley, John F.; Richers, Sherwood; Guan, Xiaoyue; Krolik, Julian H.

doi:10.1088/0004-637x/772/2/102

Cited by 131 publications

(173 citation statements)

References 41 publications

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“…As discussed in Section 4.5, the dimensionless numbers, such as α, α m , and B 2 r /B 2 φ , measured in the bound gas are similar to the values reported by Hawley et al (2013) and Jiang et al (2013a). Vertical structures of the disk at each radius, such as the radiation pressure supported optically thick part and strong corona above the photosphere for effective absorption opacity, are also consistent with local shearing box simulations (Jiang et al 2013a(Jiang et al , 2014b.…”

Section: Local Versus Global Modelssupporting

confidence: 82%

A Global Three-Dimensional Radiation Magneto-Hydrodynamic Simulation of Super-Eddington Accretion Disks

Jiang

Stone

Davis

2014

ApJ

407

477

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We study super-Eddington accretion flows onto black holes using a global three-dimensional radiation magneto-hydrodynamical simulation. We solve the time-dependent radiative transfer equation for the specific intensities to accurately calculate the angular distribution of the emitted radiation. Turbulence generated by the magneto-rotational instability provides self-consistent angular momentum transfer. The simulation reaches inflow equilibrium with an accretion rate ∼220 L Edd /c 2 and forms a radiation-driven outflow along the rotation axis. The mechanical energy flux carried by the outflow is ∼20% of the radiative energy flux. The total mass flux lost in the outflow is about 29% of the net accretion rate. The radiative luminosity of this flow is ∼10 L Edd . This yields a radiative efficiency ∼4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in most models, such as the slim disk model, which neglect vertical advection. Our inferred radiative efficiencies also exceed published results from previous global numerical simulations, which did not attribute a significant role to vertical advection. We briefly discuss the implications for the growth of supermassive black holes in the early universe and describe how these results provided a basis for explaining the spectrum and population statistics of ultraluminous X-ray sources.

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Section: Local Versus Global Modelssupporting

confidence: 82%

A Global Three-Dimensional Radiation Magneto-Hydrodynamic Simulation of Super-Eddington Accretion Disks

Jiang

Stone

Davis

2014

ApJ

407

477

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“…Hawley, Gammie & Balbus 1995;Sorathia et al 2012;Hawley et al 2013) confirmed that MRI can sustain turbulence and dynamo in accretion discs. However, semi-analytical and numerical simulations (see, for example, Masada & Sano 2008;Stone 2011;Hawley et al 2013;Suzuki & Inutsuka 2014;Nauman & Blackman 2015) suggest that the total (Reynolds + Maxwell) stresses due to MRI are insufficient to cause the effective angular momentum transfer in accretion discs in terms of the phenomenological alpha-parameter α S S (Shakura & Sunyaev 1973), giving rather low values α S S ∼ 0.01 − 0.03. Note that from the observational point of view, the alpha-parameter can be reliably evaluated, e.g., from the analysis of non-stationary accretion discs in X-ray novae (Suleimanov, Lipunova & Shakura 2008), dwarf-nova and AM CVn stars (Kotko & Lasota 2012), and turns out to be an order of magnitude higher than typically found in the numerical MRI simulations.…”

Section: Introductionmentioning

confidence: 79%

“…Non-linear numerical simulations (e.g. Hawley, Gammie & Balbus 1995;Sorathia et al 2012;Hawley et al 2013) confirmed that MRI can sustain turbulence and dynamo in accretion discs. However, semi-analytical and numerical simulations (see, for example, Masada & Sano 2008;Stone 2011;Hawley et al 2013;Suzuki & Inutsuka 2014;Nauman & Blackman 2015) suggest that the total (Reynolds + Maxwell) stresses due to MRI are insufficient to cause the effective angular momentum transfer in accretion discs in terms of the phenomenological alpha-parameter α S S (Shakura & Sunyaev 1973), giving rather low values α S S ∼ 0.01 − 0.03.…”

Section: Introductionmentioning

confidence: 96%

On properties of Velikhov–Chandrasekhar MRI in ideal and non-ideal plasma

Шакура¹,

Постнов²

2015

Monthly Notices of the Royal Astronomical Society

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Conditions of Velikhov-Chandrasekhar magneto-rotational instability in ideal and non-ideal plasmas are examined. Linear WKB analysis of hydromagnetic axially symmetric flows shows that in the Rayleigh-unstable hydrodynamic case where the angular momentum decreases with radius, the MRI branch becomes stable, and the magnetic field suppresses the Rayleigh instability at small wavelengths. We investigate the limiting transition from hydromagnetic flows to hydrodynamic flows. The Rayleigh mode smoothly transits to the hydrodynamic case, while the Velikhov-Chandrasekhar MRI mode completely disappears without the magnetic field. The effects of viscosity and magnetic diffusivity in plasma on the MRI conditions in thin accretion discs are studied. We find the limits on the mean free-path of ions allowing MRI to operate in such discs.

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“…This is a particularly constraining problem in global simulations. Recently, the convergence and the effect of resolution in global adiabatic (Hawley et al 2013) and locally isothermal (Parkin & Bicknell 2013) simulations were investigated. A convergence study in fully radiative global simulations is difficult to achieve and would go beyond the scope of this paper.…”

Section: Effect Of Resolution Equation Of State and Dust-to-gas Masmentioning

confidence: 99%

Radiation magnetohydrodynamics in global simulations of protoplanetary discs

Flock

Fromang

González

et al. 2013

A&A

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Aims. Our aim is to study the thermal and dynamical evolution of protoplanetary discs in global simulations, including the physics of radiation transfer and magneto-hydrodynamic turbulence caused by the magneto-rotational instability. Methods. We have developed a radiative transfer method based on the flux-limited diffusion approximation that includes frequency dependent irradiation by the central star. This hybrid scheme is implemented in the PLUTO code. The focus of our implementation is on the performance of the radiative transfer method. Using an optimized Jacobi preconditioned BiCGSTAB solver, the radiative module is three times faster than the magneto-hydrodynamic step for the disc set-up we consider. We obtain weak scaling efficiencies of 70% up to 1024 cores. Results. We present the first global 3D radiation magneto-hydrodynamic simulations of a stratified protoplanetary disc. The disc model parameters were chosen to approximate those of the system AS 209 in the star-forming region Ophiuchus. Starting the simulation from a disc in radiative and hydrostatic equilibrium, the magneto-rotational instability quickly causes magneto-hydrodynamic turbulence and heating in the disc. We find that the turbulent properties are similar to that of recent locally isothermal global simulations of protoplanetary discs. For example, the rate of angular momentum transport α is a few times 10 −3 . For the disc parameters we use, turbulent dissipation heats the disc midplane and raises the temperature by about 15% compared to passive disc models. The vertical temperature profile shows no temperature peak at the midplane as in classical viscous disc models. A roughly flat vertical temperature profile establishes in the optically thick region of the disc close to the midplane. We reproduce the vertical temperature profile with viscous disc models for which the stress tensor vertical profile is flat in the bulk of the disc and vanishes in the disc corona. Conclusions. The present paper demonstrates for the first time that global radiation magneto-hydrodynamic simulations of turbulent protoplanetary discs are feasible with current computational facilities. This opens up the window to a wide range of studies of the dynamics of the inner parts of protoplanetary discs, for which there are significant observational constraints.

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Testing Convergence for Global Accretion Disks

Cited by 131 publications

References 41 publications

A Global Three-Dimensional Radiation Magneto-Hydrodynamic Simulation of Super-Eddington Accretion Disks

A Global Three-Dimensional Radiation Magneto-Hydrodynamic Simulation of Super-Eddington Accretion Disks

On properties of Velikhov–Chandrasekhar MRI in ideal and non-ideal plasma

Radiation magnetohydrodynamics in global simulations of protoplanetary discs

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