Ion acoustic solitary structures in a collisionless unmagnetized plasma consisting of nonthermal electrons and isothermal positrons

TL;DR

This paper investigates ion acoustic solitary structures in a collisionless, unmagnetized plasma with nonthermal electrons and isothermal positrons using the Sagdeev pseudo-potential method, revealing conditions for solitons, double layers, and supersolitons.

Contribution

It introduces a detailed analysis of ion acoustic solitary structures considering nonthermal electron effects and identifies the existence regimes of various nonlinear structures including supersolitons.

Findings

Negative potential double layers restrict negative solitons.

Positive potential double layers occur below a critical positron-to-electron velocity ratio.

Positive potential supersolitons are observed in certain parameter regimes.

Abstract

Employing the Sagdeev pseudo-potential technique the ion acoustic solitary structures have been investigated in an unmagnetized collisionless plasma consisting of adiabatic warm ions, nonthermal electrons and isothermal positrons. The qualitatively different compositional parameter spaces clearly indicate the existence domains of solitons and double layers with respect to any parameter of the present plasma system. The present system supports the negative potential double layer which always restricts the occurrence of negative potential solitons. The system also supports positive potential double layers when the ratio of the average thermal velocity of positrons to that of electrons is less than a critical value. However, there exists a parameter regime for which the positive potential double layer is unable to restrict the occurrence of positive potential solitary waves and in this region of the parameter space, there exist positive potential solitary waves after the formation of a positive potential double layer. Consequently, positive potential supersolitons have been observed. The nonthermality of electrons plays an important role in the formation of positive potential double layers as well as positive potential supersolitons. The formation of positive potential supersoliton is analysed with the help of phase portraits of the dynamical system corresponding to the ion acoustic solitary structures of the present plasma system.