Large amplitude ion-acoustic solitons in warm negative ion plasmas with superthermal electrons

Kishan Kumar,M. K. Mishra

doi:10.1063/1.4996267

Abstract

Large amplitude ion-acoustic solitons are investigated in a plasma consisting of warm adiabatic positive and negative-ions and hot superthermal electrons having kappa distributions. Using Pseudo-potential method an energy integral equation is derived for the system. The latter is analysed to examine the existence regions of the solitary waves. It is found that negative ion concentration (α), spectral index (k) and ionic temperature ratio (σ1 or σ2) significantly influence the characteristic of the solitons. Our numerical analysis shows that the system also supports rarefactive solitons for some selected set of plasma parameters. It is also found that large amplitude ion-acoustic compressive and rarefactive solitons exist simultaneously for the same values of plasma parameters. Further an increase in the superthermality (i.e. decreasing the value of spectral index k) leads to shrinking the existing domain of the large amplitude ion-acoustic solitons. The amplitude of the compressive/rarefactive solitons increases with the increase in negative ion concentration (α). Whereas, on increasing ionic temperature ratio (σ1 or σ2) the amplitude of the compressive/rarefactive soliton decreases. The effect of negative-ion concentration (α), temperature ratio of two ion species (σ1 and σ2), Mach number (M) and spectral index (k) on the characteristics of solitons are discussed in detail. The results of the present investigation may be helpful to understand the nonlinear ion-acoustic solitary waves in space plasma and laboratory plasmas, where two distinct groups of ions and non-Boltzmann distribution electrons are present.

Highlights

In a dispersive and nonlinear medium solitary waves evolve as solitons due to exact balance of nonlinearity and dispersion
Our analysis is more general than the earlier studies of large amplitude ion-acoustic solitons and our results reduce to those obtained by Saini et al.[51] in the limit of α = 0, σ1 = 0, σ2 = 0 and εz = 1
It is found that the system supports large amplitude rarefactive ion acoustic solitons for the selected set of plasma parameters

Summary

Introduction

In a dispersive and nonlinear medium solitary waves evolve as solitons due to exact balance of nonlinearity and dispersion. Washimi and Taniuti[1] were the first to show that the propagation of ionacoustic solitary waves in a plasma can be governed by the Korteweg-de Vries (KdV) equation. The first experimental observation of ion-acoustic solitons was made by Ikezi et al.[2] Later on there has been a great deal of interest in the theoretical[3,4,5,6,7,8] and experimental[9,10,11,12,13,14,15] study of KdV and modified KdV (m-KdV) ion-acoustic solitons in multicomponent plasmas consisting of positive ions, electrons and negative ions. Al[18] and Roy et al.[19] During the last few years, negative ion plasmas attracted attention due to their importance in Laboratory experiments and space plasma observations. Negative ion plasmas are found in neutral beam sources,[24] plasma processing reactors[25] and in low temperature laboratory experiments.[26,27,28,29] Due to the presence of negative ions, the number

Objectives

Discussion

Conclusion