  We propose a new electromagnetic-emission mechanism in magnetized, force-free
plasma, which is driven by the evolution of the underlying dynamic spacetime.
In particular, the emission power and angular distribution of the emitted
fast-magnetosonic and Alfv\'en waves are separately determined. Previous
numerical simulations of binary black hole mergers occurring within magnetized
plasma have recorded copious amounts of electromagnetic radiation that, in
addition to collimated jets, include an unexplained, isotropic component which
becomes dominant close to merger. This raises the possibility of multimessenger
gravitational-wave and electromagnetic observations on binary black hole
systems. The mechanism proposed here provides a candidate analytical
characterization of the numerical results, and when combined with previously
understood mechanisms such as the Blandford-Znajek process and
kinetic-motion-driven radiation, allows us to construct a classification of
different electromagnetic radiation components seen in the inspiral stage of
compact-binary coalescences.
