  The equations governing the interaction between incoherent light and
electron-acoustic waves are presented. The modulational instability properties
of the system are studied, and the effect of partially coherent light is
discussed. It is shown that partial coherence of the light suppresses the
modulational instability. However, short wavelength perturbations are less
affected, and will therefore dominate in, e.g. pulse filamentation. The results
may be of importance to space plasmas and laser-plasma systems.
