We present three-dimensional ( 3-D ) magnetohydrodynamical ( MHD ) simulations of radiatively inefficient accretion flow around black holes .
General relativistic effects are simulated by using the pseudo-Newtonian potential .
We start calculations with a rotating torus threaded by localized poloidal magnetic fields with plasma beta , a ratio of the gas pressure to the magnetic pressure , \beta = 10 and 100 .
When the bulk of torus material reaches the innermost region close to a central black hole , a magnetically driven jet emerges .
This magnetic jet is derived by vertically inflating toroidal fields ( ‘ magnetic tower ’ ) and has a two-component structure : low- \beta ( \lower 2.0 pt \hbox { $ \buildrel \scriptstyle < \over { \scriptstyle \sim } $ } 1 ) plasmas threaded with poloidal ( vertical ) 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 .
The black hole is surrounded by quasi-spherical zone with highly inhomogeneous structure in which toroidal fields are dominant except near the rotation axis .
Mass accretion takes place mainly along the equatorial plane .
Comparisons with other MHD simulation results and observational implications are discussed .