THE MODULATION OF RADIATION IN AN ELECTRON-POSITRON PLASMA

The modulational instability of a large-amplitude, linearly polarized electromagnetic wave propagating in an electron-positron plasma is con sidered, including the combined effect of relativistic mass variation of the plasma particles, harmonic generation, and the non-resonant, fi nite-frequency electrostatic density perturbations, all caused by the large-amplitude radiation field. The radiation from many strong source s, such as AGN and pulsars, has been observed to vary over a host of t ime-scales. It is possible that the extremely rapid variations in the non-thermal continuum of AGN, as well as in the non-thermal radio radi ation from pulsars, can be accounted for by the modulational instabili ties to which radiation may be subjected during its propagation out of the emission region.