Ion Acoustic Solitons in Impurity‐Containing Plasmas

Abstract

Localized nonlinear ion acoustic waves are investigated for plasmas containing impurity ions or negatively charged dust particles. It is found that dark as well as the usual bright ion acoustic solitions can exist.The study of plasmas containing impurity ions or charged dust grains is important [l-71 for the understanding of many astrophysical phenomena, such as asteroids, planetary rings, cometary tails and interstellar clouds, as well as the Earth's space environment, such as the ionosphere, noctilucent clouds and auroras. It is also relevant to many laboratory and technological plasmas, such as low-temperature rf and dc glow discharges, rf plasma etching and the wall region fusion plasmas, as well as to the understanding of many modern materials, such as semi-conductors, optical fibers and dusty crystals. The dust particles in most plasmas of interest are of micron or submicron size, which is usually much less than the Debye length [8,9]. They can have Iarge mass and are negatively charged with large charge numbers (2, up to lo3). The grain charge can be due to field emission, ultraviolet irradiation, microscopic plasma currents, etc.Presence of massive impurity ions or charged dust particles in a plasma can significantly affect its dispersion and other linear and nonlinear properties [lo-171. In particular, they can result in the appearance of new normal modes, such as the dust-acoustic waves [12,14], which involve oscillations at such low frequencies that the electrons and ions remain in local equilibrium and the wave dynamics is mainly due to the motion of the heavy dust particles. Recently, the nonlinear evolution of the dust acoustic waves [12] and the formation of ion Langmuir envelope solitons [lv], in which the low-frequency component is the dust acoustic mode and the high-frequency carrier is the short wavelength ion acoustic (ion Langmuir) wave, have been investigated. On the other hand, the effect of negatively charged impurity particles on the nonlinear evolution of the ordinary ion acoustic waves has not been studied. In many laboratory and industrial plasmas, the ion acoustic mode is more relevant than the dust acoustic mode, since the latter involves a time scale which is much larger than the existence time of the plasma.We shall study the nonlinear behavior of ion acoustic waves for plasmas containing negatively charged impurity ions or constant-charge dust particles. In particular, we consider the existence and propagation of ion acoustic solitions. First, the governing equations are derived without approximation in the quasistationary frame moving with the wave structure and the Sagdeev potential analyzed for the existence of localized potential structures. In ')

Nonlinear dust-ion-acoustic waves in a multi-ion plasma with trapped electrons

“…It is important to note that (1)-(8) form a complete set of equations to describe the purely electrostatic perturbation mode under consideration, and that in the continuity equation for heavy negative ion fluid (1), which is coupled with (6) via (2) and (3), we have neglected the source and sink terms (which do not lose any physics insight) as neglected by many authors [3,27,28,[41][42][43][44][45][46][47][48]. The equilibrium state of the dusty multi-ion plasma system under consideration is defined as…”

Dust-ion-acoustic shock waves due to dust charge fluctuation

“…The nonlinear waves associated with the DIA waves, particularly the DIA solitary [9] and shock waves [10] have also received a great deal of interest in understanding the basic properties of localized electrostatic perturbations in space and laboratory dusty plasmas [5][6][7][8][9][10]12,13].…”

Effects of ion-fluid temperature on dust-ion-acoustic solitons

“…The DIA solitary waves have been investigated by several authors [10][11][12][13]. However, all these investigations [10][11][12][13] are limited to a cold ion-fluid limit (T i = 0).…”

“…The linear properties of the DIA waves in dusty plasmas are now well understood from both theoretical and experimental points of view [1,[3][4][5][6][7][8][9]. The DIA solitary waves have been investigated by several authors [10][11][12][13]. However, all these investigations [10][11][12][13] are limited to a cold ion-fluid limit (T i = 0).…”