Turbulent acceleration of superthermal electrons

In a recent paper it was suggested on the basis of weak turbulence theory that the collisionality of a plasma, coupled with nonlinear wave-particle interaction, is crucial for the acceleration of electrons by Langmuir turbulence to a superthermal energy level. In this Letter, fully nonlinear Vlasov and particle-in-cell (PIC) simulation techniques are employed to further verify this potentially important finding. The previous conclusion is fully confirmed by observing the expected difference between the Vlasov and PIC simulation results in the weak beam regime. However, in the strong beam regime, both the Vlasov and PIC simulations are found to produce a high-energy tail population, which indicates that there may be other mechanisms in the high beam speed situation, that are responsible for the generation the superthermal electrons. (C) 2007 American Institute of Physics.