The effect of wave reflection on induced Raman scattering in an inhomogeneous plasma

We consider the Raman back-scatter instability produced by an electromagnetic wave in a plasma whose density increases in the direction of propagation. It is shown that, when reflexion of the waves involved in the interaction is taken into account, it may be possible to obtain, in the linear approximation, normal modes that grow exponentially in time. This is in contrast to the theory that neglects refiexion, and focuses attention only on the region of resonant interaction, which predicts only spatial amplification.