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 jot 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 timcscales at the original torus position and a subsequent quasi-steady state starts.