ONE-DIMENSIONAL VLASOV SIMULATIONS OF LANGMUIR SOLITONS

Interactions of Langmuir solitons with plasma are simulated using a one-dimensional electrostatic Vlasov code, including both electrons and ions. The Zakharov's solutions are used as initial conditions. The wave is found to transfer energy into electrons during the heating process due to the interaction of resonant electrons with high-frequency electric fields. For T-e much greater than T-i, the temporal evolution of the electron distribution function shows different heating behaviors depending on whether the electrons are interacting with a single soliton or many solitons. In single-soliton interactions, the final electron distribution function approaches an exponential form, f(upsilon)proportional to exp(-6 upsilon/upsilon(te)). However, for multisoliton interactions, the final stage of the heated electrons establishes a power-law distribution function, f(upsilon)proportional to upsilon(-4), which agrees with that of Gorev and Kingsep [Sov. Phys. JETP 39, 1008 (1974)]. Simulation results for soliton motion show strong ion Landau damping, such that the solitons dissipated quickly when T-i = T-e. Analyses indicate that nonlinear damping of Langmuir solitons by thermal ions for upsilon(g) less than or equal to upsilon(ti) plays the most important role in slowing down the moving solitons. A double-hump structure was also found in the near-sonic soliton motion. (C) 1995 American Institute of Physics.