  FU Orionis (FUOR) outbursts are major optical brightening episodes in
low-mass protostars that correspond to rapid mass-accretion events in the
innermost region of a protostellar disc. The outbursts are accompanied by
strong outflows, with the inferred mass outflow rates reaching ~10% of the mass
inflow rates. Shu et al. proposed that the outflows represent accreted disc
material that is driven centrifugally from the spun-up surface layers of the
protostar by the stellar magnetic field. This model was critiqued by Calvet et
al., who argued that it cannot reproduce the photospheric absorption-line
shifts observed in the prototype object FU Ori. Calvet et al. proposed that the
wind is launched, instead, from the surface of the disc on scales of a few
stellar radii by a non-stellar magnetic field. In this paper we present results
from numerical simulations of disc accretion on to a slowly rotating star with
an aligned magnetic dipole moment that gives rise to a kilogauss-strength
surface field. We demonstrate that, for parameters appropriate to FU Ori, such
a system can develop a strong, collimated disc outflow of the type previously
identified by Romanova et al. in simulations of protostars with low and
moderate accretion rates. At the high accretion rate that characterizes FUOR
outbursts, the radius at which the disc is truncated by the stellar magnetic
field moves much closer to the stellar surface, but the basic properties of the
outflow, which is launched from the vicinity of the truncation radius along
opened-up stellar magnetic field lines, remain the same, and are distinct from
those of the mechanism proposed by Shu et al. We show that the simulated
outflow can in principle account for the main observed characteristics of FUOR
winds, including the photospheric line shifts measured in FU Ori.
