Large amplitude solitary waves in ion-beam plasmas with charged dust impurities

The nonlinear propagation of large amplitude dust ion-acoustic (DIA) solitary waves (SWs) in an ion-beam plasma with stationary charged dusts is investigated. For typical plasma parameters relevant for experiments [J. Plasma Phys. \textbf{60}, 69 (1998)], when the beam speed is larger than the DIA speed ($v_{b0}\gtrsim1.7c_s$), three stable waves, namely the "fast" and "slow" ion-beam modes and the plasma DIA wave are shown to exist. These modes can propagate as SWs in the beam plasmas. However, in the other regime ($c_s<v_{b0}<1.7c_s$), one of the beam modes when coupled to the DIA mode may become unstable. The SWs with positive (negative) potential may exist when the difference of the nonlinear wave speed ($M$) and the beam speed is such that $1.2\lesssim M-v_{b0}\lesssim1.6$ ($M-v_{b0}\gtrsim1.6$). Furthermore, for real density perturbations, the wave potential $(>0)$ is found to be limited by a critical value which typically depends on $M$, $v_{b0}$ as well as the ion/beam temperature. The conditions for the existence of DIA solitons are obtained and their properties are analyzed numerically in terms of the system parameters. While the system supports both the compressive and rarefactive large amplitude SWs, the small amplitude solitons exist only of the compressive type. The theoretical results may be useful for observation of soliton excitations in laboratory ion-beam driven plasmas as well as in space plasmas where the charged dusts play as impurities.
Comment: 8 pages, 6 figures; Article to appear in Phys. Plasmas (2011)