  We present the results of a global, three-dimensional magnetohydrodynamics
simulation of an accretion disk with a rotating, weakly magnetized central
star. The disk is threaded by a weak, large-scale poloidal magnetic field, and
the central star has no strong stellar magnetosphere initially. Our simulation
investigates the structure of the accretion flows from a turbulent accretion
disk onto the star. The simulation reveals that fast accretion onto the star at
high latitudes occurs even without a stellar magnetosphere. We find that the
failed disk wind becomes the fast, high-latitude accretion as a result of
angular momentum exchange mediated by magnetic fields well above the disk,
where the Lorentz force that decelerates the rotational motion of gas can be
comparable to the centrifugal force. Unlike the classical magnetospheric
accretion scenario, fast accretion streams are not guided by magnetic fields of
the stellar magnetosphere. Nevertheless, the accretion velocity reaches the
free-fall velocity at the stellar surface due to the efficient angular momentum
loss at a distant place from the star. This study provides a possible
explanation why Herbig Ae/Be stars whose magnetic fields are generally not
strong enough to form magnetospheres also show indications of fast accretion. A
magnetically driven jet is not formed from the disk in our model. The
differential rotation cannot generate sufficiently strong magnetic fields for
the jet acceleration because the Parker instability interrupts the field
amplification.
