Radial mixing in protoplanetary accretion disks

Keller, Ch.; Gail, H. P.

doi:10.1051/0004-6361:20034629

Cited by 74 publications

(85 citation statements)

References 22 publications

(32 reference statements)

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“…However, the observations show significant fractions of crystalline dust at least out to radii corresponding to a temperature of 100 K. Crystalline dust is also found in comets, which are formed in regions much colder than 800 K (Wooden et al 1999;Keller et al 2006). This suggests an efficient radial mixing mechanism to transport crystalline material from the hot inner disk to the colder outer parts (Nuth 1999;Bockelée-Morvan et al 2002;Keller & Gail 2004). …”

Section: Observations and Previous Model Resultsmentioning

confidence: 99%

Sub-Keplerian accretion onto circumstellar disks

Visser¹,

Dullemond²

2010

A&A

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Context. Models of the formation, evolution and photoevaporation of circumstellar disks are an essential ingredient in many theories of the formation of planetary systems. The ratio of disk mass over stellar mass in the circumstellar phase of a disk is for a large part determined by the angular momentum of the original cloud core from which the system was formed. While full 3D or 2D axisymmetric hydrodynamical models of accretion onto the disk automatically treat all aspects of angular momentum, this is not so trivial for 1D and semi-2D viscous disk models. Aims. Since 1D and semi-2D disk models are still very useful for long-term evolutionary modelling of disks with relatively little numerical effort, we investigate how the 2D nature of accretion affects the formation and evolution of the disk in such models. A proper treatment of this problem requires a correction for the sub-Keplerian velocity at which accretion takes place. Methods. We develop an update of our semi-2D time-dependent disk evolution model to properly treat the effects of sub-Keplerian accretion. The new model also accounts for the effects of the vertical extent of the disk on the accretion streamlines from the envelope. Results. The disks produced with the new method are smaller than those obtained previously, but their mass is mostly unchanged. The new disks are a few degrees warmer in the outer parts, so they contain less solid CO. Otherwise, the results for ices are unaffected. The 2D treatment of the accretion results in material accreting at larger radii, so a smaller fraction comes close enough to the star for amorphous silicates to be thermally annealed into crystalline form. The lower crystalline abundances thus predicted correspond more closely to observed abundances than did earlier model predictions. We argue that thermal annealing followed by radial mixing must be responsible for at least part of the observed crystalline material.

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Section: Observations and Previous Model Resultsmentioning

confidence: 99%

Sub-Keplerian accretion onto circumstellar disks

Visser¹,

Dullemond²

2010

A&A

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“…Here, the mass flows radially outward near the midplane compensated by increased radial inflow at upper layers of the disk to allow for net-accretion, for α < 0.05. Much emphasis was given to this radial outflow and its role for the radial transport for grains and chemical species over large distances and relative short time scales (Keller & Gail 2004;Ciesla 2009). …”

Section: Introductionmentioning

confidence: 99%

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

Flock

Dzyurkevich

Klahr

et al. 2011

ApJ

127

177

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We present full 2π global 3-D stratified MHD simulations of accretion disks. We interpret our results in the context of proto-planetary disks. We investigate the turbulence driven by the magneto-rotational instability (MRI) using the PLUTO Godunov code in spherical coordinates with the accurate and robust HLLD Riemann solver. We follow the turbulence for more than 1500 orbits at the innermost radius of the domain to measure the overall strength of turbulent motions and the detailed accretion flow pattern.We find that regions within two scale heights of the midplane have a turbulent Mach number of about 0.1 and a magnetic pressure two to three orders of magnitude less than the gas pressure, while outside three scale heights the magnetic pressure equals or exceeds the gas pressure and the turbulence is transonic, leading to large density fluctuations. The strongest large-scale density disturbances are spiral density waves, and the strongest of these waves has m = 5. No clear meridional circulation appears in the calculations because fluctuating radial pressure gradients lead to changes in the orbital frequency, comparable in importance to the stress gradients that drive the meridional flows in viscous models. The net mass flow rate is well-reproduced by a viscous model using the mean stress distribution taken from the MHD calculation.The strength of the mean turbulent magnetic field is inversely proportional to the radius, so the fields are approximately force-free on the largest scales. Consequently the accretion stress falls off as the inverse square of the radius.

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“…Its extent depends on a variety of factors including magnetic field morphology, X-ray activity, abundance of metals, and dust properties (Ilgner & Nelson 2006). The 2D disk models by Keller & Gail (2004) and Tscharnuter & Gail (2007) show the possible presence of large-scale circulation (Urpin 1984;Regev & Gitelman 2002), but such motions would be suppressed by turbulence on the scale of the disk thickness. These meridional flows may be artifacts of the 2D-hydrodynamical disk models with fixed α viscosity.…”

Section: Introductionmentioning

confidence: 99%

Chemistry in disks

Guilloteau

Dutrey

Wakelam

et al. 2012

A&A

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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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Radial mixing in protoplanetary accretion disks

Cited by 74 publications

References 22 publications

Sub-Keplerian accretion onto circumstellar disks

Sub-Keplerian accretion onto circumstellar disks

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

Chemistry in disks

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