Pulse-Stimulated Radiation from a Plasma at Harmonics of the Gyrofrequency

Abstract

A magneto-plasma excited by two short microwave pulses at the electron gyrofrequency or a multiple thereof, which have a time separation τ, is considered in the single particle approach. Due to non-linearities there arise after the second pulse, radiation maxima at the gyrofrequency and its harmonics. In a situation where the time separation of these maxima is τ* (in the simplest case τ* = τ) at the fundamental, it is τ*/n at the n-th harmonic. As the resonances at the harmonics are a finite Larmor radius effect, excitation at these frequencies requires a non-zero initial energy. As an example, the case is studied where the first pulse is at the gyrofrequency and the second at the second harmonic. In this case radiation maxima at 2ω_c occur at times t_ℓ = ℓτ (ℓ = 1, 2, 3...) after the second pulse, at the fundamental, maxima arise at times t_ℓ = (2ℓ - 1)τ. If there is no non-linearity involved other than the non-linear driving force, during the second pulse there arises only one radiation maximum at t = τ.

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