Coexistence of Arbitrary Amplitude Compressive and Rarefactive Positron-Acoustic Solitons in a Non-Maxwellian Unmagnetized Multicomponent Plasma

The present investigation concerns the study of large-amplitude positron-acoustic solitary waves (PASWs) in four-component unmagnetized plasma exhibiting non-Maxwellian characteristics. The plasma model comprises cold inertial positrons, electrons described by a Cairns distribution, hot positrons governed by a Maxwellian distribution, and stationary ions. Sagdeev’s method is employed to derive the energy integral equation, which demonstrates the existence of both positive and negative polarity PASWs under appropriate plasma conditions. A comprehensive analysis is performed to determine the effect of various plasma parameters, including hot positron concentration, electron concentration, hot positron and electron temperature ratios, the Mach number, and the nonthermal parameter—which significantly influence the formation, amplitude, and width of these PASWs, as well as their existence regions. The findings suggest a possible association of these nonlinear structures with electrostatic perturbations observed in various laboratory plasmas and astrophysical environments, including the interstellar medium, pulsar magnetospheres, active galactic nuclei, and auroral acceleration regions.