  The acceleration of an outflow along inclined magnetic field lines emanating
from an accretion disc can be studied in the local approximation, as employed
in the computational model known as the shearing box. By including the slow
magnetosonic point within the computational domain, the rate of mass loss in
the outflow can be calculated. The accretion rates of mass and magnetic flux
can also be determined, although some effects of cylindrical geometry are
omitted. We formulate a simple model for the study of this problem and present
the results of one-dimensional numerical simulations and supporting
calculations. Quasi-steady solutions are obtained for relatively strong
poloidal magnetic fields for which the magnetorotational instability is
suppressed. In this regime the rate of mass loss decreases extremely rapidly
with increasing field strength, or with decreasing surface density or
temperature. If the poloidal magnetic field in an accretion disc can locally
achieve an appropriate strength and inclination then a rapid burst of ejection
may occur. For weaker fields it may be possible to study the launching process
in parallel with the magnetorotational instability, but this will require
three-dimensional simulations.
