  I show in this paper that two types of magnetic torques can appear in the
interaction between an accretion disc and a magnetic accretor. There is the
well-known torque resulting from the difference in angular velocity between the
accretion disc and the star, but in addition there is a torque coming from the
interaction between the stellar magnetic field and the disc's own magnetic
field. The latter form of magnetic torque decreases in strength more slowly
with increasing radius, and will therefore dominate at large radii. The
direction of the disc field is not determined by the difference in angular
velocity between the star and the disc as in the Ghosh & Lamb model, but is
rather a free parameter. The magnetic torque may therefore either spin up or
spin down the star, and the torque changes sign if the magnetic field in the
disc reverses. I suggest that this mechanism can explain the torque reversals
that have been observed in some disc-fed X-ray pulsars.
