The global structure of thin, stratified <i>α</i>-discs  and the reliability of the one layer approximation

Huré, Jean-Marc; Galliano, F.

doi:10.1051/0004-6361:20000005

Cited by 11 publications

(9 citation statements)

References 19 publications

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“…For case 2, from 3 to 15 R g , the thickness calculated from the canonical model is about two to three times that of the simulated disc, while the theoretical 1D temperature is larger than the simulated one by about 30–35 per cent. So we confirm the result of Hurè & Galliano (2001), who compared vertically averaged (i.e. 1D) models of accretion discs with the corresponding vertically explicit (i.e.…”

Section: Discussionsupporting

confidence: 89%

Ab initiosimulations of accretion disc instability

Teresi

Molteni

Toscano

2004

Monthly Notices of the Royal Astronomical Society

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We show that accretion discs, both in the subcritical and supercritical accretion rate regime, may exhibit significant amplitude luminosity oscillations. The luminosity time behaviour has been obtained by performing a set of time-dependent two-dimensional smoothed particle hydrodynamics simulations of accretion discs with different values of α and accretion rate. In this study, to avoid any influence of the initial disc configuration, we produced the discs injecting matter from an outer edge far from the central object. The period of oscillations is 2-50 s for the two cases, and the variation amplitude of the disc luminosity is 10 38 -10 39 erg s −1 . An explanation of this luminosity behaviour is proposed in terms of limit cycle instability; the disc oscillates between a radiation pressure dominated configuration (with a high luminosity value) and a gas pressure dominated one (with a low luminosity value). The origin of this instability is the difference between the heat produced by viscosity and the energy emitted as radiation from the disc surface (the well-known thermal instability mechanism). We support this hypothesis showing that the limit cycle behaviour produces a sequence of collapsing and refilling states of the innermost disc region.

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Section: Discussionsupporting

confidence: 89%

Ab initiosimulations of accretion disc instability

Teresi

Molteni

Toscano

2004

Monthly Notices of the Royal Astronomical Society

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“…Huré & Galliano (2001) already noticed that the flat vertically averaged disc model is a good approximate of an active disc; we have now demonstrated that a two-layer model is a faithful description of discs both illuminated by the central star and heated by viscosity. However there are still some discrepancies:…”

Section: Comparison With Other Modelsmentioning

confidence: 57%

The vertical structure of T Tauri accretion discs

Lachaume

Malbet

Monin

2003

A&A

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Abstract. We present a two-layer accretion disc model developed to simultaneously fit optical long baseline visibilities and spectral energy distributions of T Tauri accretion discs. This model allows us to access easily the physical conditions in the disc as the mid-plane or the surface temperature. Our model includes viscous heating, absorption of stellar irradiation, and thermalisation with the surrounding medium. The disc is modelled with concentric cylinders for which the vertical radiation transfer is computed using two layers with vertically averaged temperatures: the outer layer is heated by the stellar irradiation and by the inner layer, and the inner layer by viscous dissipation and by the outer layer. We investigate three prescriptions for the geometrical thickness of the disc: it is either proportional the scale height (model 1), given ad hoc (model 2), or zero (model 3). We then derive the disc structure in the case of the α and β viscosity prescriptions, as well as for various optical thickness regimes of the disc. This analytical model allows us to disentangle regions where the mid-plane temperature and the effective temperature are dominated by accretion from regions dominated by reprocessing of stellar light. In the case of α-prescription, we find that the structure of model 2 gives predictions very close to those of numerical simulations from previous authors. From the disc structure, we derive the spectral energy distributions, images and interferometric visibilities. We analyse the influence of the disc parameters on the resulting structure and on the observable outputs. We apply our model to interpret consistently the spectral energy distributions and visibilities of SU Aur and FU Ori for which interferometric data are available, and that are not known to be part of a multiple system. We were not able to derive a consistent fit for T Tau North, which might come from caveats in the flux correction from its South component, but were able to separately derive fits for its spectrum and its visibilities. We find that even a single interferometric measurement at one infrared wavelength can bring a very strong constraint on disc models. We predict that future massive interferometric observations of accretion discs will provide a breakthrough in the understanding of accretion disc physics.

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“…If the estimated flux F est (0) in the first calculation is not sufficiently small, that is |F est (0)/F (H)| < 10 −4 , a new H is chosen, estimated through a Newton-Raphson method. Given the initial disk radius R D , α-parameter and the initial accretion rate, we can thus calculate density, temperature and pressure profiles at any time t. Huré and Galliano (2001) reports of a 30% maximum deviation on the midplane temperature comparing one-dimensional and two-dimensional models.…”

Section: Two-dimensional Modelmentioning

confidence: 99%

On the origin of elemental abundances in the terrestrial planets

Elser

Meyer

Moore

2012

Icarus

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The abundances of elements in the Earth and the terrestrial planets provide the initial conditions for life and clues as to the history and formation of the Solar System. We follow the pioneering work of Bond et al. (2010a) and combine circumstellar disk models, chemical equilibrium calculations and dynamical simulations of planet formation to study the bulk composition of rocky planets. We use condensation sequence calculations to estimate the initial abundance of solids in the circumstellar disk with properties determined from time dependent theoretical models. We combine this with dynamical simulations of planetesimal growth that trace the solids during the planet formation process and which include the effects of gravitational and hydrodynamical mixing. We calculate the elemental abundances in the resulting rocky planets and explore how these vary with the choice of disk model and the initial conditions within the Solar Nebula.Although certain characteristics of the terrestrial planets in the Solar System could be reproduced, none of our models could reproduce the abundance properties of all the planets. We found that the choice of the initial planetesimal disk mass and of the disk model has a significant effect on composition gradients. Disk models that give higher pressure and temperature result in larger variations in the bulk chemical compositions of the resulting planets due to inhomogeneities in the element abundance profiles and due to the different source regions of the planets in the dynamical simulations. We observed a trend that massive planets and planets with relatively small semi-major axes are more sensitive to these variations than smaller planets at larger radial distance. Only these large variations in the simulated chemical abundances can potentially explain the diverse bulk composition of the Solar System planets, whereas Mercury's bulk composition can not be reproduced in our approach.

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The global structure of thin, stratified α-discs and the reliability of the one layer approximation

Cited by 11 publications

References 19 publications

Ab initiosimulations of accretion disc instability

Ab initiosimulations of accretion disc instability

The vertical structure of T Tauri accretion discs

On the origin of elemental abundances in the terrestrial planets

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