  We investigate generation of electromagnetic radiation by gravitational waves
interacting with a strong magnetic field in the vicinity of a vibrating
Schwarzschild black hole. Such an effect may play an important role in
gamma-ray bursts and supernovae, their afterglows in particular. It may also
provide an electromagnetic counterpart to gravity waves in many situations of
interest, enabling easier extraction and verification of gravity wave waveforms
from gravity wave detection. We set up the Einstein-Maxwell equations for the
case of odd parity gravity waves impinging on a static magnetic field as a
covariant and gauge-invariant system of differential equations which can be
integrated as an initial value problem, or analysed in the frequency domain. We
numerically investigate both of these cases. We find that the black hole
ringdown process can produce substantial amounts of electromagnetic radiation
from a dipolar magnetic field in the vicinity of the photon sphere.
