Nonlinear Stabilization of the Ion-Beam-Cyclotron Instability

The nonlinear evolution of a single, coherent, electrostatic, ion-cyclotron wave driven unstable by a cold-ion beam directed along the magetic field is studied. When the beam energy density is large compared to the thermal energy density of the background plasma, saturation occurs by the nonlinear ion gyrofrequency shift of the background ions. Saturation amplitudes are estimated and nonlinear oscillations and solitons are shown to occur.