  Neutron stars have solid crusts threaded by strong magnetic fields.
Perturbations in the crust can excite non-radial oscillations, which can in
turn launch Alfven waves into the magnetosphere. In the case of a compact
binary close to merger involving at least one neutron star, this can happen
through tidal interactions causing resonant excitations that shatter the
neutron star crust. We present the first numerical study that elucidates the
dynamics of Alfven waves launched in a compact binary magnetosphere. We seed a
magnetic field perturbation on the neutron star crust, which we then evolve in
fully general-relativistic force-free electrodynamics using a GPU-based
implementation. We show that Alfven waves steepen nonlinearly before reaching
the orbital light cylinder, form flares, and dissipate energy in a transient
current sheet. Our results predict radio and X-ray precursor emission from this
process.
