Suppression of Raman Scattering in Modulated Plasma With the Oblique Orientation of Density Ripples

Abstract

The phenomenon of stimulated Raman scattering (SRS) is investigated in under-dense rippled plasma with the proposal of an oblique orientation of density ripples in plasma. The dispersion relation is derived using the fluid theory, and a specific case is examined for the coupling of higher phase velocity Langmuir wave to lower phase velocity Langmuir wave generated due to stationary rippled electron density. This coupling leads to dissipation of the wave energy through Landau damping of the latter wave, which results in the suppression of temporal growth of the SRS. The growth rate of the SRS is found to decrease up to a specific value with the increasing ripples density amplitude <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\eta $ </tex-math></inline-formula> and the decreasing wavenumber <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \vec {q}\vert $ </tex-math></inline-formula> . The presence of the rippled electron density not only leads to the dissipation of the wave energy but also decreases the region of resonance where the SRS takes place.