Contribution to half-harmonic splitting resulting from Raman backscattering in a rippled plasma

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Abstract
The dispersion relation of electron plasma waves in a rippled plasma is analyzed. The ripple couples the plasma wave to its spatial harmonics thereby introducing ‘‘forbidden’’ frequency bands. It is shown that the stimulated Brillouin scattering (SBS) induced ripple can directly influence the frequency matching condition for Raman near the quarter‐critical density and thereby lead to an asymmetric splitting of the half‐harmonic radiation. The predicted blue‐shifted peak is found to be more sensitive to the ripple amplitude than the red‐shifted peak. This mechanism may contribute to the half‐harmonic splitting that is observed in many experiments.