Abstract
Progress in understanding the nonlinear ion acoustic solitary waves which accompany collisionless electron–positron–ion plasmas with high-energy electrons and positrons (represented by kappa distribution) is presented. Both small and arbitrary amplitude solitary waves are investigated by deriving Korteweg–de Vries equation and energy-integral equation (involving a Sagdeev-like pseudopotential), respectively. The existence regions of the solitary pulses are defined precisely. Furthermore, numerical calculations reveal that only supersonic pulses may exist. The dependence of the solitary excitation characteristics on the superthermal parameters, the ion temperature, and the Mach number have been investigated. The present studies might be helpful to understand the excitation of nonlinear ion acoustic solitary pulses in interstellar medium.