  The interaction of a rotating star's magnetic field with a surrounding plasma
disk lies at the heart of many questions posed by neutron stars in X-ray
binaries. We consider the opening of stellar magnetic flux due to differential
rotation along field lines coupling the star and disk, using a simple model for
the disk-opened flux, the torques exerted on the star by the magnetosphere, and
the power extracted by the electromagnetic wind. We examine the conditions
under which the system enters an equilibrium spin state, in which the accretion
torque is instantaneously balanced by the pulsar wind torque alone. For
magnetic moments, spin frequencies, and accretion rates relevant to accreting
millisecond pulsars, the spin-down torque from this enhanced pulsar wind can be
substantially larger than that predicted by existing models of the
disk-magnetosphere interaction, and is in principle capable of maintaining spin
equilibrium at frequencies less than 1 kHz. We speculate that this mechanism
may account for the non-detection of frequency increases during outbursts of
SAX J1808.4-3658 and XTE J1814-338, and may be generally responsible for
preventing spin-up to sub-millisecond periods. If the pulsar wind is collimated
by the surrounding environment, the resulting jet can satisfy the power
requirements of the highly relativistic outflows from Cir X-1 and Sco X-1. In
this framework, the jet power scales relatively weakly with accretion rate, L_j
~ Mdot^{4/7}, and would be suppressed at high accretion rates only if the
stellar magnetic moment is sufficiently low.
