Envelope excitations of ion acoustic solitary waves in a plasma with superthermal electrons and positrons

Theoretical studies of the nonlinear self-modulation of ion acoustic waves (IAWs) in an electron-positron-ion plasma with superthermal electrons are carried out. By using the standard reductive perturbation method (RPM), the nonlinear Schrodinger equation (NLSE) is derived. The stability analysis, based on a nonlinear Schrodinger-type equation, exhibits a wide instability region, which depends on spectral index (kappa), ratio of positron to electron density (p) and electron to positron temperature ratio (sigma). It is found that these parameters modify the nature of modulational instability (MI) for IAWs and associated envelope solitary structures. Further, the effect of these parameters on the growth rate of MI is discussed.