Ion Acoustic Solitary Waves and Double-Layers in a Plasma with Nonthermal Electrons and Positrons

The effects of nonthermal electron distribution and ion temperature are incorporated in the investigation of nonlinear ion acoustic waves in a pair-ion plasma. Sagdeev pseudo- potential method which takes into account the full nonlinearity of the plasma equations is used to study solitary wave solutions. It is shown that there is a region in parameter space where both negative and positive potential can coexist. For the fixed value of nonthermal electrons, it is found that the effect of increase in ion temperature is to reduce the range of co-existence of compressive and rarefactive solitons. Particular concentration of nonthermal electrons results in disappearance of rarefactive solitons while the decrease in ion temperature, at this concentration restores the lost rarefactive solitons. Also, the existence of rarefactive double layers solitons is investigated. It is found that the nonthermal electrons and ion-temperature play significant role in determining the region of the existence of double layers.