  Using numerical relativity simulations with a subgrid dynamo prescription to
generate strong initial magnetic fields, we investigate the possibility of
launching a jet-like outflow from the hypermassive neutron star (HMNS) during
the early stages of the merger, prior to the remnants collapse to a black hole.
We demonstrate that buoyant instabilities in the strongly magnetized HMNS can
lead to a periodic emission of powerful electromagnetic flares shortly after
the merger. These are followed by a collimated mildly relativistic outflow.
Both types of outflows feature quasi-periodic kilohertz substructure. These
early-time outflows may power precursors to short-duration gamma-ray bursts
(SGRB) or in some cases the entire SGRB. While the overall temporal power
spectrum we find broadly agrees with the one recently reported for
quasi-periodic oscillations in the SGRB GRB910711, our simulations suggest that
the periodic electromagnetic substructure is dominated by magnetohydrodynamic
shearing processes rather than correlating with the corresponding post-merger
gravitational wave signal.
