Application of bicoherence analysis in study of wave interactions in space plasma

Abstract

A spectral analysis at the second order (power spectrum) loses the phase information among the different Fourier components. To retain this information, the bispectrum (third order) and/or the bicoherence (normalized bispectrum) are calculated. Application to simulated data, shows the dependence of the bispectrum to amplitudes of involved waves and of the bicoherence to signal‐to‐noise ratio. Bicoherence technique is applied in the analysis of harmonics produced by an electronic receiver, as well as in the investigation of phase coherence between a ground‐transmitter signal, a natural ELF emission near the proton gyrofrequency, and the sidebands around the carrier. Strong arguments are provided that the sidebands are generated by a parametric interaction between the transmitter signal and the ELF emission.