  Jets, from the protostellar to the AGN context, have been extensively studied
but their connection to the turbulent dynamics of the underlying accretion disc
is poorly understood. Following a similar approach to Lesur et al. (2013), we
examine the role of the magnetorotational instability (MRI) in the production
and acceleration of outflows from discs. Via a suite of one-dimensional
shearing-box simulations of stratified discs we show that magneto-centrifugal
winds exhibit cyclic activity with a period of 10-20 Omega^{-1}, a few times
the orbital period. The cycle seems to be more vigorous for strong vertical
field; it is robust to the variation of relevant parameters and independent of
numerical details. The convergence of these solutions (in particular the mass
loss rate) with vertical box size is also studied. By considering a sequence of
magnetohydrostatic equilibria and their stability, the periodic activity may be
understood as the succession of the following phases: (a) a dominant MRI
channel mode, (b) strong magnetic field generation, (c) consequent wind
launching, and ultimately (d) vertical expulsion of the excess magnetic field
by the expanding and accelerating gas associated with the wind. We discuss
potential connections between this behaviour and observed time-variability in
disk-jet systems.
