Abstract

The present paper carries out a particle-in-cell (PIC) simulation in order to validate the recently formulated theory of electromagnetic fluctuations emitted spontaneously in thermal magnetized plasmas (Yoon and Lopez 2017 Phys. Plasmas 24 022117). Numerical plots of theoretically constructed fluctuation spectra and computer simulated fluctuation spectra are compared. While the two results produce an overall favorable agreement for subluminous regime in angular frequency versus wave number space, namely, the domain characterized by phase speed less than the speed of light in vacuo, the present PIC simulation also shows that fluctuation spectra are highly enhanced in the close vicinity of linear eigenmodes, which includes superluminal range that does not satisfy the linear cyclotron wave-particle resonance condition. Since the theory of electromagnetic spontaneous emission, which is based upon linear plasma response and linear wave-particle resonant interactions, strictly forbids emissions in such a regime, the PIC code simulation can only be understood in terms of nonlinear wave-particle interaction. This calls for nonlinear generalization of the spontaneous emission theory.