A reduced nonlinear model of synergy between wave-particle and wave-wave interactions

In this work, we investigate the synergetic interactions between wave-particle and wave-wave couplings within a hybrid system of fluid and kinetic models, through generalizing the Berk-Breizman-Pekker model. In this extended model, the wave-wave interaction is described by a fluid nonlinearity, while the wave-particle interaction is described by the kinetic nonlinearity. Two types of nonlinear wave-wave interactions are investigated numerically. At the early stage of the frequency chirping, the indirect wave-wave interaction can dominate over the direct one. When the chirped frequency difference is relatively large and the collision coefficients are appropriate, the direct interaction can become the primary wave-wave coupling process. In this scenario, the saturation level of waves is constrained to a finite value regardless of collision coefficients.