Non-linear gravitational wave interactions with plasmas
  We consider the interactions of a strong gravitational wave with electromagnetic fields using the 1+3 orthonormal tetrad formalism. A general system of equations are derived, describing the influence of a plane fronted parallel (pp) gravitational wave on a cold relativistic multi-component plasma. We focus our attention on phenomena that are induced by terms that are higher order in the gravitational wave amplitude. In particular, it is shown that parametric excitations of plasma oscillations takes place, due to higher order gravitational non-linearities. The implications of the results are discussed. 
Gert Brodin, Mattias Marklund and Peter K.S. Dunsby