Alfven-ion-cyclotron turbulence induced by the electromagnetic ion-cyclotron instability

Turbulence driven by the parametric instability of the Alfven-ion-cyclotron (AIC) waves is investigated by using a particle-in-cell simulation method. The AIC waves with a broad range are excited by the anisotropic ion temperature. In addition, harmonic modes and upper sideband modes of AIC waves are found. In the longitudinal electrostatic fluctuations, the ion-acoustic (IA) waves and its second harmonic (IA^2nd) modes are found. The mode coupling between the excited fluctuations is investigated by using the bicoherence analysis. It is also shown that the electrostatic field shows a single spectrum which corresponds to IA^2nd waves, whereas density fluctuation shows a dual spectrum of IA and IA^2nd waves. The charge neutrality condition normally applied for the IA mode breaks down for the IA^2nd mode.