Study of nonlinear interaction of plasma wave using higher order spectrum in whistler frequency range

Various types of wave phenomena in the whistler frequency range have been studied in the ionosphere-magnetosphere system in past, which specify the significance of wave-wave interactions in the space plasma. In our work we shall be paying attention on spectrum broadening processes which can be unified by the parametric (nonlinear) interaction of whistler mode waves with ionosphere and magnetospheres plasma [1]. These effects are enlightening on the basis of whistler wave interactions with small-scale plasma irregularities and quasi-electrostatic lower-hybrid resonance (LHR) waves. This process is analogous to the parametric interaction of high-frequency (HF) radio waves in the ionosphere F-layer near the reflection level [2].An analytical study of nonlinear-mode coupling between the VLF transmitter pulse and natural ELF/VLF emissions during the spectrum broadening by bicoherence analysis has been done by many researchers [3, 4, 5, 6]. Therefore in this attempt we analyses the nonlinear wave-wave interaction in whistler frequency range by wavelet bicoherence analysis. In past the bicoherence analysis computed over the Fourier modes of the VLF signal but due to the non-stationary and non-Gaussian nature of VLF signal, we compute the bicoherence by a better tool termed as wavelet transform. The wavelet bicoherence mathematically define as [7]