Interpretation of bi-coherence in space and lab plasma-wave dynamics

Responsible bi-coherence analysis and hypothesis-testing requires adequate sampling and resolution. This investigation focuses on the assessment of temporal dynamics associated with the bispectrum cross-phase and amplitude. We detect, document and interpret wave-wave coupling evidenced in time series from interacting toroidal Alfven eigenmodes arising in DIII-D tokamak plasma, from super-low-frequency (0.02 - 10 millihertz) resonances near magnetospheric boundaries as measured by the Cluster satellite instruments, from a forced van der Pol oscillator, and from various audio signals, both recorded and contrived. We monitor the adjustable plasma parameters in the tokamak, natural time-varying conditions in the solar wind, driving-force frequency and amplitude in the van der Pol oscillator, and spectral content in the audio synthesizer. Examples of wave-wave interaction, daughter-wave generation, driven-oscillator phenomena, sideband production, and beat-wave coupling will be presented. The generality of the method is an advantage for interpreting nonlinear waves and processes across a variety of experimental platforms.