Dynamics of ion acoustic waves in electronegative plasmas

Abstract

The main purpose of the present study is to investigate how electronegative plasmas parameters namely, the negative ions concentration ratio (α) and the electron-to-negative ions temperature ratio (σn) modify the ion acoustic structures. We study the ion acoustic waves in an unmagnetized electronegative plasma made of Boltzmann electrons, Boltzmann negative ions and cold mobile positive ions. In one dimensional analysis, the reductive perturbation method is used to reduce the dynamics of the whole system to a cubic nonlinear Schrödinger equation, whose the nonlinear and dispersion coefficients, P and Q, are function of the negative ion parameters. The study of MI is used to show the correlation between the parametric analysis and the formation of modulated solitons obtained here as bright envelopes and kink-wave solitons. Furthermore, weakly relativistic ion acoustic waves are investigated in an electronegative plasma. Analytical solutions, in the form of rogue waves, are thereafter presented and their response to plasma parameters changes is discussed. In two dimensional investigation, the governing hydrodynamic equations are reduced to a Davey-Stewartson system, which is used to study the MI of ion acoustic waves along with the effect of plasma parameters. Numerically, parameters from the instability regions give rise to series of dromion solitons under the activation of modulational instability. The sensitivity of the numerical solutions to plasma parameters is discussed. Some exact solutions in the form of one- and two-dromion solutions are derived and their response to the effect of varying (α) and (σn) is discussed as well. In three-dimensional electronegative plasma model, modulated ion-acoustic waves are investigated via the activation of the modulational instability in the Davey-Stewartson equations. The contributions of the modulation angle and electronegative plasma parameters are discussed to that effect, including some particular cases such as the parallel and transverse modulations. Otherwise, the dynamics of coupled ion acoustic waves is introduced. Using the reductive perturbation technic, it is showed that the system can fully be described using a set of two coupled Schrödinger equations.