Electrostatic triple root structures: Connections to supersolitons, double layers, and acoustic speed solitons in nonthermal plasmas with negative and positive dust

Abstract

Large-amplitude dust-acoustic solitons and double layers in a dusty plasma model comprised of nonthermal Cairns electrons and ions, and cold, negative and positive dust grains had earlier been investigated, before newer concepts such as supersolitons, solitons at the acoustic speed, and even acoustic speed supersolitons arose. It turned out that under certain conditions, three distinct roots of the same polarity coalesce into a triple root, so that now a systematic investigation is carried out into the existence domains and properties of triple root solitary structures. From the analysis of the Sagdeev pseudopotentials, it transpires that there is a wide range of compositional parameters and soliton speeds where triple root structures can exist, and these are shown to be intimately connected with double layer and supersoliton ranges. Thus, triple roots are much more common than at first expected, even at the acoustic speed or in the presence of Boltzmann rather than Cairns nonthermal hot species. Once the existence domains are properly established, as many examples can be worked out as one chooses, generating typical soliton or double layer and electric field profiles. A great many combinations of compositional parameters and soliton speeds have been numerically tested, and they all reveal a similar pattern, with quantitative but no inherent qualitative changes.