Solitons at the critical density of negative ions in multicomponent plasmas

The derivation of solitary waves in generalized multicomponent plasmas shows that the negative ion introduces a critical density at which the characteristics of the solitons are studied. The soliton´s behavior derived using the Korteweg-deVries (KdV) equation at the critical density shows that the nonlinearity of the wave vanishes. Thus the mode of study is augmented through a modified KdV equation. Using a higher-order equation involving quadratic and cubic nonlinearities, the transition of the KdV equation to a modified KdV equation along with the conservation of the Sagdeev potential, which is not affected by the negative ions, is studied in detail. The results are compared with experimental observations, especially those made by Y. Nakamura et al. (J. Plasma Phys., vol.33, p.237-48, 1985)