Radial mixing in protoplanetary accretion disks

Free access article

Issue		A&A Volume 378, Number 1, October IV 2001


Page(s)		192 - 213
Section		Formation and evolution of planetary systems
DOI		http://dx.doi.org/10.1051/0004-6361:20011130

A&A 378, 192-213 (2001)
DOI: 10.1051/0004-6361:20011130

I. Stationary disc models with annealing and carbon combustion

H.-P. Gail

Institut für Theoretische Astrophysik, Universität Heidelberg, Tiergartenstraße 15, 69121 Heidelberg, Germany

(Received 5 January 2001 / Accepted 8 August 2001 )

Abstract
The interplay between radial mixing process in protoplanetary accretion discs with processes leading to destruction or modification of the extinction properties of abundant dust species has significant consequences for the properties of the disk. This paper studies the consequences of annealing amorphous silicate dust at $T\approx 800$ K, of combustion of the carbon dust component at about $T\approx1000$ K and of mixing the products into cold outer disc regions out to 10 AU and beyond. A model calculation in the one-zone approximation for stationary Keplerian $\alpha$ -disks around a solar-like protostar is combined with a solution of the equations for annealing of silicate dust grains, for carbon dust oxidation, and a solution of the diffusion equations for radial mixing of the dust components in the disc by turbulent flows. It is shown that annealing of amorphous silicate dust reduces the mass extinction coefficient of the disc matter by more than an order of magnitude in the warm disc zone. Radial mixing of the freshly produced crystalline silicate dust into outer disc regions reduces the opacity of the disc material also in cold disc regions where annealing is not possible. Mixing of carbon dust free material from the zone of carbon combustion into outer disc regions also leads to a considerable reduction of the opacity of the disc material. Radial mixing processes then modify the dust composition of the outer disc regions and by means of the dependence of the disk properties (midplane temperature $T\rm _c$ , viscosity $\nu$ , ...) on the opacity also modify the structure and evolution of a protoplanetary disc. It is shown that turbulent mixing processes in the protoplanetary accretion disc of a Solar System like system during its evolution prior to the onset of the formation of planetary bodies carry material from inner disc regions r< 1 AU outwards to at least 10...20 AU. This offers a simple explanation of the findings that a significant fraction of the cometary silicate dust grains are crystallised and that the matrix material of primitive meteorites contains thermally processed crystalline dust material.

Key words: accretion disks -- molecular processes -- solar system: formation

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.