EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 429/ 1 Article

Free access article

Issue A&A
Volume 429, Number 1, January I 2005
Page(s) 1 - 13
Section Astrophysical processes
DOI http://dx.doi.org/10.1051/0004-6361:200400065



A&A 429, 1-13 (2005)
DOI: 10.1051/0004-6361:200400065

A hydrodynamic shear instability in stratified disks

B. Dubrulle1, L. Marié1, Ch. Normand2, D. Richard1, 3, F. Hersant4, 5 and J.-P. Zahn3

1  GIT/SPEC/DRECAM/DSM, CNRS, URA 2464, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
    e-mail: bdubrulle@cea.fr
2  SPHT/DSM, CNRS, URA 2306 CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
3  LUTH, Observatoire de Paris, 92195 Meudon, France
4  Institut für Theoretische Astrophysik, Heidelberg, Germany
5  LESIA, Observatoire de Paris, 92195 Meudon, France

(Received 27 November 2002 / Accepted 5 August 2004 )

Abstract
We discuss the possibility that astrophysical accretion disks are dynamically unstable to non-axisymmetric disturbances with characteristic scales much smaller than the vertical scale height. The instability is studied using three methods: one based on the energy integral, which allows the determination of a sufficient condition of stability, one using a WKB approach, which allows the determination of the necessary and sufficient condition for instability and a last one by numerical solution. This linear instability occurs in any inviscid stably stratified differential rotating fluid for rigid, stress-free or periodic boundary conditions, provided the angular velocity  $\Omega$ decreases outwards with radius  r. At not too small stratification, its growth rate is a fraction of  $\Omega$. The influence of viscous dissipation and thermal diffusivity on the instability is studied numerically, with emphasis on the case when ${\rm d} \ln \Omega / {\rm d} \ln r =-3/2$ (Keplerian case). Strong stratification and large diffusivity are found to have a stabilizing effect. The corresponding critical stratification and Reynolds number for the onset of the instability in a typical disk are derived. We propose that the spontaneous generation of these linear modes is the source of turbulence in disks, especially in weakly ionized disks.


Key words: accretion, accretion disks -- hydrodynamic -- instabilities -- turbulence




© ESO 2004

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.