Non-linear generation of combination frequencies in a plasma

Abstract

In this paper the authors have considered the generation of combination frequencies due to two strong uniform parallel electric fields of frequencies ω₁ and ω₂ in a homogeneous plasma; it is found necessary to introduce terms containing exp {i(ω₁ ± ω₂)t} in f_o (the symmetrical part of the distribution function f) and f₂ (the higher-order asymmetrical part appearing as the third term in a Legendre polynomial expansion of f), because their contributions to the combination frequency components of current density are appreciable. The growth of the combination frequency waves in a plasma and their appearance in the reflected waves from a plasma-free-space interface when two electromagnetic waves of frequencies ω₁ and ω₂ are propagating along the same direction (normal to the interface) has also been studied. Some numerical results have been presented in the discussion at the end.