Turbulence and Steady Flows in Three-Dimensional Global Stratified Magnetohydrodynamic Simulations of Accretion Disks

Flock, Mario; Dzyurkevich, Natalia; Klahr, Hubert; Turner, Neal J.; Henning, Th.

doi:10.1088/0004-637x/735/2/122

Cited by 127 publications

(213 citation statements)

References 84 publications

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“…This profile is in qualitative agreement with results of isothermal local simulations (Simon et al 2012), as well as in radiative MHD local simulations (Hirose et al 2006;Flaig et al 2010), and in locally isothermal global MHD simulations (Fromang & Nelson 2006). By normalizing the stress over the local pressure (blue curve), we also obtain a vertical profile and absolute α values similar to isothermal simulations (Flock et al 2011). The accretion stress α amounts to about 10 −3 in the disc equatorial plane and increases up to a few times 10 −1 in the corona.…”

Section: Resultssupporting

confidence: 88%

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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Section: Resultssupporting

confidence: 88%

Radiation magnetohydrodynamics in global simulations of protoplanetary discs

Flock

Fromang

González

et al. 2013

A&A

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“…Fromang & Nelson (2006) and Flock et al (2011) show that the velocity dispersion increases quickly with height above two scale heights (with the c s /Ω K definition, i.e. at √ 2H(r) with our definition).…”

Section: Discussionmentioning

confidence: 84%

“…However, shearing box simulations of MRI induced turbulence by Simon et al (2011) show no evidence for such anisotropy. On the other hand, Flock et al (2011) and Fromang & Nelson (2006) find small anisotropy, the radial velocity fluctuations being about 1.5-2 times larger than in the azimuthal or vertical directions.…”

Section: Discussionmentioning

confidence: 85%

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Chemistry in disks

Guilloteau

Dutrey

Wakelam

et al. 2012

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Context. Turbulence is thought to be a key driver of the evolution of protoplanetary disks, regulating the mass accretion process, the transport of angular momentum, and the growth of dust particles. Aims. We intend to determine the magnitude of the turbulent motions in the outer parts (>100 AU) of the disk surrounding DM Tau. Methods. Turbulent motions can be constrained by measuring the nonthermal broadening of line emission from heavy molecules. We used the IRAM Plateau de Bure interferometer to study emission from the CS molecule in the disk of DM Tau. High spatial (1.4 × 1. ) and spectral resolution (0.126 km s −1 ) CS J = 3-2 images provide constraints on the molecule distribution and velocity structure of the disk. A low sensitivity CS J = 5-4 image was used in conjunction to evaluate the excitation conditions. We analyzed the data in terms of two parametric disk models, and compared the results with detailed time-dependent chemical simulations.Results. The CS data confirm the relatively low temperature suggested by observations of other simple molecules. The intrinsic linewidth derived from the CS J = 3-2 data is much larger than expected from pure thermal broadening. The magnitude of the derived nonthermal component depends only weakly on assumptions about the location of the CS molecules with respect to the disk plane. Our results indicate turbulence with a Mach number around 0.4-0.5 in the molecular layer. Geometrical constraints suggest that this layer is located near one scale height, in reasonable agreement with chemical model predictions.

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“…Nevertheless, if the scale-height of a disk is higher, as in the case of BD disks, the scale of turbulent structures increases, leading to higher pressure scales (e.g. Flock et al 2011).…”

Section: Radial Drift and Pressure Bumpsmentioning

confidence: 99%

Explaining millimeter-sized particles in brown dwarf disks

Pinilla

Birnstiel

Benisty

et al. 2013

A&A

120

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Context. Planets have been detected around a variety of stars, including low-mass objects, such as brown dwarfs. However, such extreme cases are challenging for planet formation models. Recent sub-millimeter observations of disks around brown dwarf measured low spectral indices of the continuum emission that suggest that dust grains grow to mm-sizes even in these very low mass environments. Aims. To understand the first steps of planet formation in scaled-down versions of T-Tauri disks, we investigate the physical conditions that can theoretically explain the growth from interstellar dust to millimeter-sized grains in disks around brown dwarf. Methods. We modeled the evolution of dust particles under conditions of low-mass disks around brown dwarfs. We used coagulation, fragmentation, and disk-structure models to simulate the evolution of dust, with zero and non-zero radial drift. For the non-zero radial drift, we considered strong inhomogeneities in the gas surface density profile that mimic long-lived pressure bumps in the disk. We studied different scenarios that could lead to an agreement between theoretical models and the spectral slope found by millimeter observations. Results. We find that fragmentation is less likely and rapid inward drift is more significant for particles in brown dwarf disks than in T-Tauri disks. We present different scenarios that can nevertheless explain millimeter-sized grains. As an example, a model that combines the following parameters can fit the millimeter fluxes measured for brown dwarf disks: strong pressure inhomogeneities of ∼40% of amplitude, a small radial extent ∼15 AU, a moderate turbulence strength α turb = 10 −3 , and average fragmentation velocities for ices v f = 10 m s −1 .

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Turbulence and Steady Flows in Three-Dimensional Global Stratified Magnetohydrodynamic Simulations of Accretion Disks

Cited by 127 publications

References 84 publications

Radiation magnetohydrodynamics in global simulations of protoplanetary discs

Radiation magnetohydrodynamics in global simulations of protoplanetary discs

Chemistry in disks

Explaining millimeter-sized particles in brown dwarf disks

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