Abstract
Rational solution of the nonlinear Schrodinger equation (NLSE) is considered to investigate the properties of the ion-acoustic freak (rogue) waves in multicomponent plasmas, whose constituents are electrons, warm positive ions, and two distinct groups of warm negative ions. For this purpose, the hydrodynamic basic equations are reduced to an extended Korteweg-de Vries (EKdV) or Gardner equation. This equation is transformed into a NLSE for investigating the weakly nonlinear wavepackets. The conditions of modulational instability and rogue waves formation are defined. It is found that sign of the coefficients of the Gardner equation determines the stability/instability of the propagating pulses within the critical wave number values. Under certain values of plasma parameters, the Gardner equation reduces to a modified KdV equation. So, a new stability/instability region will be pinpointed. The rogue waves characteristics and their dependence on the plasma parameters of Xe+ -F--SF6- and Ar+ F--SF6- plasma experiments are highlighted.