Coexistence of positive and negative potential nonlinear structures in a two positive ion plasma with Cairns distributed electrons

The effects of electron nonthermality on the stopbands in a two positive ion plasma, comprising a cold positive ion species, a warm positive ion species, and Cairns distributed electrons were investigated by Maharaj and Bharuthram. In this study, we extend the study by Maharaj and Bharuthram, and investigate the existence of negative solitons and their coexistence with positive solitons in the same plasma model. It is found that, depending on the combination of the plasma parameter values, the coexistence of solitary waves of both polarities exists in three different combinations: coexistence of positive KdV with negative non-KdV solitons, coexistence of positive non-KdV with negative KdV solitons, and coexistence of positive KdV with negative KdV solitons. The effects of the cold ion charge-to-mass ratio on the stopbands and the solitary wave existence and coexistence domains in the plasma parameter space are also investigated.