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Proposing Institution

Max Planck Institute for Astrophysics
Project Manager

Dr. Matteo Bugli
Karl-Schwarzschild-Straße 1
85748 Garching
Accretion onto black holes is one of the most powerful and efficient mechanisms in the Universe in producing high-energy radiation, providing the central engine of powerful astronomical sources such as active galactic nuclei, X-ray binaries, and gamma-ray bursts, to cite a few. Numerical simulations have proved in the last decade to be an invaluable tool in modeling the regions close to the central black hole, often making use of the ideal MHD (magnetohydrodynamic) approximation in a relativist framework. As of today, it is still not clear whether global simulations of magnetized thick accretion flows converge to physically reasonable results (and if yes, to what extent). It is, therefore, crucial to systematically assess the reliability of their conclusions and check their dependence on numerical parameters, initial conditions and physical phenomena included in the algorithms.This project's aim is to investigate some important aspects related to global simulations of thick magnetized tori orbiting around rotating black holes, which can influence our general understanding and interpretation of current state-of-the-art MHD simulations in General Relativity (GRMHD).Using the GRMHD code ECHO, we investigate the role of numerical and physical resistivity, and hence the consequences of a substantial dissipation of the magnetic fields on the dynamical evolution of the accretion flow. We will test the stability of recently developed analytic solutions describing magnetized tori with generic distributions of angular momentum and check whether different radial boundary conditions (describing the infall of material launched in a relativistic jet back into the central black hole) can set a feedback on the power in the jet generated by the accretion process. Finally, we will study the importance of the specific implementation of our code by comparing some of its results with those coming from a list of other GRMHD codes, thus proving insights on the reliability of global GRMHD simulations and suggestions on their further improvement.

Impressum, Conny Wendler