Modified Korteweg–deVries solitons in a warm plasma with negative ions

Abstract

The propagation of ion-acoustic solitons in a warm plasma in the presence of negative ions has been investigated theoretically through the modified Korteweg–deVries (KdV) equation. In the case of the first-order velocity perturbation of the positive ions bearing a constant ratio to that of the negative ions, the existence of both compressive and rarefactive solitons at different critical densities for different temperature ratios has been established when the mass ratio is greater than unity. It is also demonstrated in this case that no modified KdV soliton exists at the critical density in a warm plasma with negative ions when the mass ratio is less than unity.