Ion Acoustic Soliton in Plasma with Negative Ion

Abstract

Ion acoustic solitons are investigated theoretically in a plasma composed of electron, positive ion and negative ion. Due to the presence of negative ion, the property of the ion acoustic soliton is drastically modified. At the critical density of the negative ion, the nonlinear coefficient of the Korteweg-de Vries equation vanishes and then the ion acoustic wave is described by the modified Korteweg-de Vries equation. The transition from the Korteweg-de Vries soliton to the modified Korteweg-de Vries soliton is also studied by means of an evolution equation with quadratic and cubic nonlinearities.