Self-Modulation and Self-Focusing of Ion Wave in Two-Electron-Temperature Plasma

Self-modulation and self-focusing of ion wave in a two-electron-temperature plasma composed of cold and hot electrons and positive ion have been theoretically investigated based on the nonlinear Schrödinger equation describing the wave. For the ion wave of large wavenumber, the modulational instability occurs irrespective of temperature and density ratios of the hot electron to the cold electron. If the temperature ratio is larger than ∼10, the ion wave of any wavenumber turns out to be unstable modulationally at a critical density ratio. The self-focusing of ion wave, on the other hand, scarcely occurs. Between two critical densities, however, the ion wave of small wavenumber becomes unstable with respect to transverse modulation if the temperature ratio is superior to ∼10.