The propagation of ion acoustic waves (IAWs) in plasmas composed of ions and nonextensive electrons and positrons is investigated. By means of the reduction perturbation technique, a nonlinear Schrödinger equation is derived and the modulation instability (MI) of ion acoustic waves is analyzed in detail. The effects of different ranges of the nonextensive parameter q on the MI are studied. The growth rate of the MI is also given for different values of the q parameter. It is also found that the ratio of the electron temperature to positron temperature and the ratio of the positron density to electron density modify the nature of IAWs instability and the solitary structures.

The head-on collision between two electronacoustic solitary waves (EASWs) in an unmagnetized plasma is investigated, including a cold electrons fluid, hot electrons, obeying a nonextensive distribution and stationary ions. By using the extended Poincaré-Lighthill-Kuo (PLK) perturbation method, the analytical phase shifts following the head-on collision are derived. The effects of the ratio of the number density of hot electrons to the number density of cold electrons α, and the nonextensive parameter q on the phase shifts are studied. It is found that q and the hot-to-cold electron density ratio significantly modify the phase shifts.

In this paper, the characteristics of the head-on collision of ion-acoustic solitary waves (IASWs) in the collisionless magnetic-field-free plasma consisting of cold ions, nonextensive electrons and thermal positrons are discussed using the extended Poincaré-Lighthill-Kuo method. Two Kortewege-de Vries equations for solitary waves are derived and the analytical phase shifts after the head-on collision of two solitary waves are also obtained. The effects of the electron nonextensive distribution (q-parameter) on the phase shifts of both the colliding solitary waves are studied. It is found that the presence of nonextensive electrons plays a significant role in the collision of IASWs.

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Cylindrical and spherical Korteweg–de Vries equations are derived for dust acoustic solitary waves in an unmagnetized three species plasma system, comprised of negatively charged cold dust, nonextensive ions and nonextensive electrons using standard reductive perturbation method. The effects of qe-nonextensive electrons, qi-nonextensive ions, electron-to-ion number density ratio μ, and nonplanar geometry on the profiles of the amplitudes of the solitary structures are examined numerically.