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EP: Fachverband Extraterrestrische Physik

EP 6: Astrophysics

EP 6.9: Talk

Tuesday, March 31, 2009, 17:20–17:35, Zahnklinik

The Influence of Radiation Transport in Protoplanetary Discs — •Ralf Kissmann, Markus Flaig, and Wilhelm Kley — Computational Physics Universität Tübingen

There is a large amount of studies of the magneto-rotational instability (MRI) in protoplanetary accretion discs available in the scientific literature. Corresponding simulations range from investigations in the local so-called shearing-box limit to global simulations of accretion discs. A major shortcoming to most of these models, however, is that the internal energy of the flow is not properly taken into account. Usually authors use an isothermal equation of state due to the fact that the use of the full energy equation will yield an ever increasing disc temperature due to the energy dissipated by the turbulence. Here we will discuss the shortcomings of this approach: apart from the fact that a constant temperature is certainly not realistic for a protoplanetary disc, we also argue that whenever a full energy equation is used radiation transport processes have to be taken into account. We will show that apart from changing the distribution of the internal energy they also have some influence on the MRI itself. We will present analytical results of this influence in the form of modified growth rates, which will be supplemented by numerical simulations yielding the modified saturation rates of the instability. Not only the saturation levels for the turbulent fluctuation energies are changed, but there is also some effect with regard to the accretion rate. From the analytical analysis it will become clear, that in contrast to viscous processes radiation transport can also enhance the instability under certain circumstances.