Ion-acoustic envelope excitations in electron–positron–ion plasma with nonthermal electrons

A theoretical investigation has been made for modulational instability of ion-acoustic waves in an electron–positron–ion plasma with nonthermal electrons. Employing reductive perturbation method (RPM), the nonlinear Schrödinger equation (NLSE) is derived. The dispersive and nonlinearity coefficients, P and Q, respectively, are the functions of nonthermal parameter (β), ratio of positron to electron density (d), ratio of the electron to positron temperature (δ) and ratio of ion to electron temperature (σ). It is observed that these parameters significantly modify the conditions of the modulational instability. The system supports both types of bright and dark envelope excitations.