HLRB Project h1222
MHD Turbulence in Accretion Disks around Black Holes
Regional Observatory, Heidelberg
Proposing Institution
Regional Observatory, Heidelberg
Project Manager
Prof. Dr. Max Camenzind
Königstuhl 12
69117 Heidelberg
Abstract
Within this project MHD turbulence in accretion discs around stellar Black Holes are investigated using the PLUTO-Code (A.Mignone et al. 2007). Following works of e.g. Balbus-Hawley 1999,2002 a pressure balanced torus embedded in a weak magnetic field is set up. The magneto-rotational instability starts to develop MHD turbulence which especially in case of an initially toroidal B-field needs a lot of computational power, also because disks around Black Holes are highly dynamical objects covering huge ranges in length and time scales. The resulting turbulence transports angular momentum outward and hence leads to accretion which itself produces the observed high luminosities and jets we can observe.Gravity is treated in a pseudo-Newtonian way following Paczynski & Wiita (1980) but the MHD module used includes special relativity. The simulations will also be fully 3D global simulations in order to capture the three dimensional properties of MHD-turbulence and the relativistic motions around Black Hole sources.Besides the comparison with classical MHD results a comparison with results obtained from previous studies done in the local shearing box approximation are planned (Fromang et al. 2007, Goodman 2006). A resolution study is needed to show if the magnetic stress necessary for accretion drops with the resolution as seen in the local approximation and if fully developed turbulence can be sustained and stabilized to maintain accretion over longer time scales. The latter issue currently is the crucial problem to solve,so within this project an attempt is made to contribute to these questions.High resolution is necessary to link the simulated accretion rates to observed luminosities and also for a decent harmonic analysis needed for analysing turbulence in Fourier-space.
