Acoustic-like modes in a two-ion quasi-neutral plasma: linear and nonlinear analysis

Abstract

A theoretical analysis of acoustic-like modes in a plasma consisting of two kinds of ions with different temperatures has been performed using fluid equations. The electrons are assumed to form a dynamic neutralizing background, and their perturbation has been neglected – which is permissible for k2λ2De ≫ 1. The analysis shows that an acoustic-like mode appears to propagate as a normal mode when the hotter ion concentration is very large compared with that of the colder ions.

Ion acoustic and dust acoustic waves at finite size of plasma particles

“…Neglecting the first term for cold dust we can rewrite formula (40) in the traditional for the dust acoustic wave form, which was obtained for the first time in Ref. [38] for point-like particles, …”

Comment on “Is dust acoustic wave a new plasma acoustic mode?” [Phys. Plasmas 4, 3427 (1997)]

“…It has recently been claimed by Dwivedi 1 that the dustacoustic wave ͑DAW͒, introduced as a theoretical concept in the seminal paper by Rao et al 2 and experimentally verified afterwards, 3 should not be viewed as a novel plasma wave, but as a special case of the so-called acoustic-like mode ͑ALM͒ introduced a year earlier by Dwivedi et al 4 There are several reasons to dispute this criticism by Dwivedi. 1 One basic reason has to do with the model used in the Dwivedi et al paper, 4 which rests physically on very dubious grounds, because it considers a plasma with two ion species in the presence of a fixed electron background.…”

“…1 One basic reason has to do with the model used in the Dwivedi et al paper, 4 which rests physically on very dubious grounds, because it considers a plasma with two ion species in the presence of a fixed electron background. This is strange, to say the least, since assuming the most mobile species to be immobile amounts mathematically to taking the limit m e →ϱ while keeping m i finite.…”

“…This is strange, to say the least, since assuming the most mobile species to be immobile amounts mathematically to taking the limit m e →ϱ while keeping m i finite. The other reason has to do with the simple fact that heavy charged dust grains are nowhere mentioned in their ALM paper 4 as being potential applications of the ͑flawed͒ theoretical treatment. Hence one cannot now claim to have foreseen DAW as being within this compass.…”

“…Quite to the contrary, charged dust is nowhere mentioned in the possible applications of the Dwivedi et al paper, 4 in which moreover an extremely dubious physical model is discussed in which the lightest species ͑electrons͒ are effectively immobile! No wonder their ill-defined ALM inspired nobody.…”