On the application of cross bispectrum and cross bicoherence

Bispectrum and bicoherence analysis is a powerful method to analyze nonlinear interaction of turbulent plasmas. In this review, we explain the difference of the bispectrum and bicoherence analysis and possible research that can be pursued with these methods. Basic concept is explained by using several examples from previous successes brought by bicoherence and bispectrum analysis, such as drift wave-zonal flow interaction. Open questions are discussed that can be challenged by these methods. Problems such as spatial transport of fluctuation energy (i.e. turbulence spreading), momentum transport by the triplet correlation, and so on, are treated. Bispectrum and bicoherence analysis can be utilized to expand the forefront of plasma turbulence research.