中文摘要：

In this paper,derived from Maxwell and fluid equations of plasmas,unified nonlinear wave equations are used to describe the parametric decay instability(PDI)in magnetized plasmas,and in view of mode-coupling,we can obtain all the possible PDI channels.By solving the nonlinear equations with a mode-coupling method,we obtain the growth rate of the PDI,of which all of the three waves are ordinary mode(O-mode)or extraordinary mode(X-mode)wave.Under the dipole approximation,an explicit formula of the growth rate of the X-mode and the condition of the equilibrium density scale are obtained.According to the existence conditions of three X-mode waves,this kind of instability might exist in ECRH with the second harmonic X-mode wave.

英文摘要：

In this paper, derived from Maxwell and fluid equations of plasmas, unified nonlinear wave equations are used to describe the parametric decay instability （PDI） in magnetized plasmas, and in view of mode-coupling, we can obtain all the possible PDI channels. By solving the nonlinear equations with a mode-coupling method, we obtain the growth rate of the PDI, of which all of the three waves are ordinary mode （O-mode） or extraordinary mode （X-mode） wave. Under the dipole approximation, an explicit formula of the growth rate of the X-mode and the condition of the equilibrium density scale are obtained. According to the existence conditions of three X-mode waves, this kind of instability might exist in ECRH with the second harmonic X-mode wave.