Vertical shear instability in accretion disc models with radiation transport

Institut für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
e-mail: moritz.stoll@student.uni-tuebingen.de; wilhelm.kley@uni-tuebingen.de

Received: 2 May 2014
Accepted: 24 September 2014

Abstract

Context. The origin of turbulence in accretion discs is still not fully understood. While the magneto-rotational instability is thought to operate in sufficiently ionised discs, its role in the poorly ionised protoplanetary disc is questionable. Recently, the vertical shear instability (VSI) has been suggested as a possible alternative.

Aims. Our goal is to study the characteristics of this instability and the efficiency of angular momentum transport, in extended discs, under the influence of radiative transport and irradiation from the central star.

Methods. We use multi-dimensional hydrodynamic simulations to model a larger section of an accretion disc. First we study inviscid and weakly viscous discs using a fixed radial temperature profile in two and three spatial dimensions. The simulations are then extended to include radiative transport and irradiation from the central star.

Results. In agreement with previous studies, for the isothermal disc we find a sustained unstable state with a weak positive angular momentum transport of the order of α ≈ 10^-4. Under the inclusion of radiative transport the disc cools off and the turbulence terminates. For discs irradiated from the central star we again find a persistent instability with a similar α value as for the isothermal case.

Conclusions. We find that the VSI can indeed generate sustained turbulence in discs, albeit at a relatively low level with α about few times 10^-4.