  In the vicinity of merging neutron strar binaries or supernova remnants,
gravitational waves can interact with the prevailing strong magnetic fields.
The resulting partial conversion of gravitational waves into electromagnetic
(radio) waves might prove to be an indirect way of detecting gravitational
waves from such sources.
  Another interesting interaction considered in this article is the excitation
of magnetosonic plasma waves by a gravitational wave passing through the
surrounding plasma. The transfer of gravitational wave energy into the plasma
might help to fuel the `fireball' of electromagnetic radiation observed in
gamma ray bursts. In the last section of the article, a dispersion relation is
derived for such magnetosonic plasma waves driven by a gravitational wave.
