Plasma instability in a strong, circularly polarized electromagnetic wave

Conclusions

In summary, we have studied the parametric instability of a cold electron plasma in a strong, circularly polarized electromagnetic wave, taking into account the relativistic nature of the electron motion. We have shown that an instability of longitudinal waves occurs at frequencies ω′≪ω_p/ϰ and ω′≈ω_p/ϰ, while an instability of transverse waves occurs at frequencies ω₀±ω′≈ω₀ and ω₀±ω_p/ϰ. The results of a numerical solution of the dispersion relation for large pump amplitudes, in which case the approximation of a weak coupling between waves is not applicable, show that the growth rates and the bands of the instabilities increase with increasing pump amplitude. We have found that in the case of the excitation of electromagnetic plasma waves, even at low pump amplitudes, the relativistic nature of the electron motion can be of decisive importance for the effect.