Magnetohydrodynamical Accretion Flows: Formation of Magnetic Tower Jet and Subsequent Quasi-Steady State

Abstract

We present three-dimensional (3-D) magnetohydrodynamical (MHD) simulations of both radiatively inefficient accretion flow (RIAF) into and jet from black holes (BHs). When the bulk of torus material reaches the innermost region close to a central BH, a magnetically driven jet emerges. This magnetic jet is derived by vertically inflating toroidal fields ('magnetic tower') and has a two-component structure: low-β (< 1) plasmas threaded with poloidal fields are surrounded by that with toroidal fields. The collimation width of the jet depends on external pressure, pressure of ambient medium; the weaker the external pressure is, the wider and the longer-lasting becomes the jet. Unless the external pressure is negligible, the bipolar jet phase ceases after several dynamical timescales at the original torus position and a subsequent quasi-steady state starts.