Global three-dimensional MHD simulations of accretion disks and jet formation in AGNS

Abstract

We present the results of three-dimensional global magnetohydrodynamic (MHD) simulations of a gas torus in active galactic nuclei. When the torus is threaded by large-scale vertical magnetic fields, a magnetically driven jet is ejected from the torus. Since magnetic braking extracts angular momentum from the torus, the surface layer of the torus accretes like an avalanche. Due to the growth of global non-axisymmetric MHD modes, the avalanching flow breaks up into spiral channels and creates a helical structure inside the jet. We found that when the torus is initially threaded by weak toroidal magnetic fields, it evolves toward a quasi-steady state with β = P gas P mag ∼ 10 . As the angular momentum is re-distributed, the torus becomes flattened and the angular momentum distribution approaches that of Keplerian disks.