J. Parashar et R. Bharuthram, Millimetre-wave second-harmonic generation in an underdense magnetoplasma with a density ripple, J PLASMA PH, 62, 1999, pp. 485-491
A high-power millimetre wave (omega(1),k(1)) propagating through a magnetiz
ed plasma at an angle to a density ripple (0,k(0)) produces density perturb
ations (omega(1), k(1), k(0)), The density perturbations couple with the os
cillatory velocity at (omega(1),k(1)) to produce a nonlinear current at (2
omega(1).2k(1) + k(0)) driving second-harmonic electromagnetic radiation. T
he efficiency of the process is sensitive to the angle between the density
ripple and the millimetre wave.