title: Re-examining the Cairns-Tsallis model for ion acoustic solitons.
abstract: Recently, a hybrid distribution function [Tribeche et al., Phys. Rev. E 85, 037401 (2012)] was proposed to describe a plasma species with an enhanced superthermal component. This combines a Cairns-type "nonthermal" form with the Tsallis theory for nonextensive thermodynamics. Using this alternative model, the propagation of arbitrary amplitude ion acoustic solitary waves in a two-component plasma is investigated. From a careful study of the distribution function it is found that the model itself is valid only for a very restricted range in the q-nonextensive parameter and the nonthermality parameter, α. Solitary waves, the amplitude and nature of which depend sensitively on both q and α, can exist within a narrow range of allowable Mach numbers. Both positive and negative potential structures are found, and coexistence may occur.
authors.affiliation: Centre for Plasma Physics, Department of Physics and Astronomy, Queen's University Belfast, BT7 1NN Northern Ireland, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Williams
authors.forename: I
authors.initials: I
authors.lastname: Kourakis
authors.forename: F
authors.initials: F
authors.lastname: Verheest
authors.forename: M A
authors.initials: MA
authors.lastname: Hellberg