  We present the results of three-dimensional global resistive
magnetohydrodynamic (MHD) simulations of black hole accretion flows. General
relativistic effects are simulated by using the pseudo-Newtonian potential.
Initial state is an equilibrium model of a torus threaded by weak toroidal
magnetic fields. As the magnetorotational instability (MRI) grows in the torus,
mass accretes to the black hole by losing the angular momentum. We found that
in the innermost plunging region, non-axisymmetric accretion flow creates
bisymmetric spiral magnetic fields and current sheets. Mass accretion along the
spiral channel creates one armed spiral density distribution. Since the
accreting matter carries in magnetic fields which subsequently are stretched
and amplified due to differential rotation, current density increases inside
the channel. Magnetic reconnection taking place in the current sheet produces
slow mode shock waves which propagate away from the reconnection site. Magnetic
energy release in the innermost plunging region can be the origin of X-ray
shots observed in black hole candidates. Numerical simulations reproduced soft
X-ray excess preceding the peak of the shots, X-ray hardening at the peak of
the shot, and hard X-ray time lags.
