A route to turbulence in nonlinear development of an ion beam–plasma instability

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Abstract
Nonlinear evolution of the ion beam–plasma instability has been investigated by means of numerical simulations based on a hybrid code. A scenario on a path to the onset of turbulence has been found as follows. The initial exponential growth of the linear instability is saturated by beam trapping, which causes, in turn, amplitude oscillation. The more highly driven harmonics initiate the stochastic instability of the trapped particles. The trapped beam particles begin to wander from one potential wave trough to another and spread in phase space. A transition to turbulence is found to occur through subharmonic excitations because of a parametric decay instability.