Acoustic solitary waves and sagdeev potential triple roots

Abstract

Both KdV theory and the standard pseudopotential theory require that solitons and double layers be explicitly super-acoustic, with the pseudopotential ψ(,M) having a maximum at the origin. Recent studies of a variety of different three-component plasmas have shown that they may support finite amplitude solitons at the true acoustic speed of the plasma configuration, Ms. These are associated with triple roots of the Sagdeev potential, and the usual soliton condition is replaced by ψ″(0,M)≤0. Sagdeev potentials for speeds marginally greater than Ms then represent solitons of both polarities, one whose amplitude vanishes at Ms (KdV-like), while the other is necessarily finite at Ms ('nonKdV-like'). Such coexistence regions have been observed to be linked to a critical plasma compositional parameter value for which ψ‴(0,Ms)=0. © 2010 American Institute of Physics.