A theoretical analysis of acoustic-like modes in a plasma consisting of two kinds of ions with different temperatures has been performed using fluid equations. The electrons are assumed to form a dynamic neutralizing background, and their perturbation has been neglected – which is permissible for k2λ2De ≫ 1. The analysis shows that an acoustic-like mode appears to propagate as a normal mode when the hotter ion concentration is very large compared with that of the colder ions.

The theoretical analysis of ion Langmuir plasma oscillations in a plasma filled in a cylindrical waveguide has been done using fluid equations. Neglecting electron perturbation, which is permissible for k⊥2λDe2 ≫ 1, the analysis shows that the propagation of such modes is possible because of the finite radius of the cylindrical waveguide. Further, it is found that in the nonlinear regime, small as well as large amplitude compressive solutions are formed.

The propagation characteristics of ion-acoustic rarefactive soliton (IARS) in a two-electron temperature plasma with two cold ion species are investigated considering the nonisothermal distributions of electrons using a kinetic model and fluid model for both ion species. Using the Sagdeev potential formalism the nonlinear dispersion relation and expression for width are derived for IARS. The variation of Mach number and width of the IARS with the amplitude is studied numerically and compared with earlier theoretical results as well as experimental observations. It is found that the results are improved qualitatively as well as quantitatively with the consideration of the presence of a suitable negative ion-impurity.

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An electron hole is discussed theoretically in an electron beam-plasma system. The nonlinear dispersion relation for the electron hole along with the conditions on the existence of the electron hole is investigated numerically. It is found that depending upon the beam parameters and radial boundary there are two regions where the electron hole can be formed. It is also seen that the upper limit on Mach number of the electron hole does not vanish even in the presence of the electron beam. The electron holes of high Mach number are possible only in the presence of an electron beam.