  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-$\beta$ ($\lsim 1$) 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.
