Simulation of parametric decay instability excited by oscillating pump near lower hybrid frequency

Abstract

Parametric decay instability of lower hybrid waves plays an important role in plasma heating. Simulation of such instability requires inclusion of both electron and ion kinetics with a realistic mass ratio. In this work, the gyrokinetic electron and fully kinetic ion (GeFi) particle simulation model is used to study parametric instabilities in uniform, magnetized plasmas. A pump electric field near the lower hybrid frequency is imposed, which is treated in the dipole approximation. Three types of parametric decay processes are obtained, including purely growing modulational instability, resonant decay instability, and non-resonant decay instability. Dependences of parametric growth rates on the wavenumber, pump strength, and pump frequency are systematically investigated. The simulation results agree well with those in the linear growth stage of parametric decay instability obtained in an existing theory. Whether electron or ion nonlinearity dominates in the parametric decay process is assessed, and the importance of the electron E×B drift in the three-wave interaction process is confirmed.