Instability and damping of one-dimensional large-amplitude plasma waves

Numerical simulations have been carried out by the particle-in-cell method for the instability and damping of one-dimensional plasma waves in the region E20/8πnT>m/M>(k0r/sub d/)2. The simulations were carried out over a broad range of initial wave properties E20/8πnTapprox.4 x 10-2--102, v/sub Phi//v/sub T/approx.3--160, and M/m = 102 or, in certain cases, M/m = 103. The most important processes are the modulational instability, with a modulation length shorter than the wavelength; wave conversion at a density inhomogeneity (the process l/sub k/0+s/sub k//sub i/ → l/sub k/0/sub plus-or-minusbetak//sub i/, where β = 1, 2, 3, . . .); and the trapping of electrons by the wave or by its harmonics. One or another of these processes will be predominant, depending on the initial properties of the wave. In the region of linear waves, E20/8πnT<10-3/(k0r/sub d/)2, the modulational instability is predominant; in the region E20/8πnTk0r/sub d/ it leads to collapse. All three processes play comparable roles in the region 4 x l0-2/(k0r/sub d/)2>E20/8πnT>10-3/ (k0r/sub d/)2. In the strong-damping region, E20/8πnT>4 x 10-2/(k0r/sub d/)2 the leading role is played by the trapping of electrons by the wave, which results in a damping much stronger than Landau damping