Boltzmann Negative Ions Research Articles

Nonlinear dust-ion acoustic solitary waves for collisional electronegative dusty plasma in the presence of trapped electron distribution

We have investigated the characteristics of nonlinear propagation of dust-ion acoustic solitary waves in collisional electronegative unmagnetized dusty plasma, which consists of trapped electrons, Boltzmann negative ions, mobile positive ions, mobile negative dust particulates, and a uniform background of neutral particles. In account of ion-neutral collisions, the modified Korteweg–de Vries relation has been derived by employing the standard reductive perturbation method. Analytical and numerical solutions of the damped Korteweg–de Vries equation has been presented in which finite difference method is used for numerical solution. On the other hand, the dust charging equation has been solved by using Newton’s Raphson method. It is found that the temperature ratio of free to trapped electrons, ion-neutral collision, concentration of negative ions, dust number density, and dust density perturbation modify the basic properties of the dust-ion acoustic solitary waves. The temporal evolution of dust-ion acoustic solitary waves is crucial as it affects the amplitude and width of wave structure. In addition, the analytical and numerical solutions are compared, and their deviation is graphically illustrated.

Modulational instability of coupled waves in electronegative plasmas

The dynamics of coupled ion-acoustic waves is investigated in an electronegative plasma made of Boltzmann negative ions, cold mobile positive ions and Boltzmann electrons. Using the reductive perturbation method, it is shown that the system can fully be described by a set of two coupled nonlinear Schrödinger equations. The parametric analysis of modulational instability reveals the existence of regions of instability that are sensitive to changes in plasma parameters such as the negative ion concentration ratio and the electron-to-negative ion temperature ratio. The analytical results are confronted to numerical simulations, where we examine the long-time dynamics of modulated waves in the electronegative plasma. One obtains the generation of nonlinear modulated waves that are sensitive to the negative-ion concentration ratio. Exact solutions for individual modes are discussed and one finally derives the coupled solution. The response of the latter to the plasma parameter variations is also addressed.

Shocks in an electronegative plasma with Boltzmann negative ions and κ-distributed trapped electrons

We derived a Schamel-Burgers equation to study the dynamics of nonlinear structures in dissipative electronegative plasma having Boltzmann negative ions and κ-distributed trapped electrons. A recently introduced Tangent hyperbolic method has been employed to get the solutions of the differential equations which contain fractional nonlinearity. The effects of different physical parameters particularly, the kinematic viscosity, the superthermality, the trapping efficiency and the electronegativity factor on the ion acoustic (IA) shock profiles have been elaborated. In case of non-dissipative electronegative plasma, the small amplitude double layers (DLs) have also been investigated. It has been elaborated that the DLs strongly depend on the system parameters. The results illustrate that the superthermality index and trapping parameter play disruptive role in the formation of DLs. Likewise, the electronegativity factor plays a dominant role in the shaping of the compressive DLs. The study can be supportive to understand the behavior of nonlinear structures as observed in the nature and laboratory plasmas.

Investigation of cylindrical shock waves in dusty plasma

Electronegative dusty plasma composed of Boltzmann electrons, Boltzmann negative ions, inertial positive ions and charge fluctuating dust has been considered. The fractional modified Burgers’ (FMB) equation, which is derived using Euler–Lagrange variational technique, is analytically obtained and solved for studying the cylindrical geometry effect on the propagation of the dust ion acoustic shock wave. The Laplace homotopy perturbation method, the so-called LHPM is applied to solve the FMB equation. The effect of the fractional parameter, positive ion number density at equilibrium, the number of equilibrium electrons residing on the dust grain surface and shock velocity on the behavior of the shock waves in the dusty plasma has been investigated.

Electronegative nonlinear oscillating modes in plasmas

The emergence of nonlinear modulated waves is addressed in an unmagnetized electronegative plasma made of Boltzmann electrons, Boltzmann negative ions and cold mobile positive ions. The reductive perturbation method is used to reduce the dynamics of the whole system to a cubic nonlinear Schrödinger equation, whose the nonlinear and dispersion coefficients, P and Q, are function of the negative ion parameters, namely the negative ion concentration ratio (α) and the electron-to-negative ion temperature ratio (σn). It is observed that these parameters importantly affect the formation of modulated ion-acoustic waves, either as exact solutions or via the activation of modulational instability. Especially, the theory of modulational instability is used to show the correlation between the parametric analysis and the formation of modulated solitons, obtained here as bright envelopes and kink-wave solitons.

Nonlinear dynamics of soliton collisions in electronegative plasmas: The phase shifts of the planar KdV- and mkdV-soliton collisions

The collisions of weakly nonlinear structures in an electronegative plasma consisting of Boltzmann electrons, Boltzmann negative ions, and cold mobile positive ions are investigated depending on experimental data. Our attention is focused on the study of the face-to-face soliton collisions, i.e. head-on soliton collisions. To do this, the extended Poincaré–Lighthill–Kuo (PLK) reductive perturbation method is used. The present study is split into two parts: the first one, called generic case. In this case, the two-coupled Korteweg–de Vries (KdV) equations and the analytical phase shifts after the head-on collision of the two-KdV solitons are obtained. Our numerical calculations, showed that both compressive and rarefactive solitons can exist in such plasma, depending on the relevant physical plasma parameters, namely the electrons-to-negative ion temperature ratio and the negative ion concentration. It is found that the phase shift has a positive sign for compressive solitary structures and negative sign for rarefactive solitary structures. At the critical value of the temperature ratio, the two-coupled modified Kortwege–de Vries (mKdV) equations are used to study the soliton collision rather than the two-KdV equations and the analytical phase shifts after the collision are derived. In the latter case (called special case), the combinations of negative and positive soliton collision can occur, contrary to the generic case, where both soliton collisions necessarily have the same polarity. The plasma parameter values for laboratory experiment are taken for discussion.

An expression for the hl factor in low-pressure electronegative plasma discharges

The positive ion flux exiting a low-pressure plasma discharge is a crucial quantity in global (volume-averaged) models. In discharges containing only electrons and positive ions (electropositive discharges), it is common to write this flux , where is the central positive ion density, is the positive ion fluid speed at the sheath edge (the Bohm speed), and is the positive ion edge-to-centre density ratio. There are well established formulae for in electropositive discharges, but for discharges containing negative ions (electronegative discharges), the analysis is more complicated. The purpose of this paper is to propose a formula for the factor in low-pressure electronegative discharges. We use the numerical solution of fluid equations with Boltzmann negative ions, including Poisson’s equation, as a guide to derive an analytical expression that can easily be incorporated in global models. The parameter space in which the derived expression is valid is discussed at the end of the paper.

ROLE OF TRAPPED ELECTRONS IN THE PROPAGATION OF DUST-ION ACOUSTIC WAVES IN MAGNETIZED DUSTY ELECTRONEGATIVE PLASMA

A theoretical investigation has been conducted concerning the nonlinear propagation of dust-ion acoustic waves in magnetized three-component dusty electronegative plasma consisting of Boltzmann negative ions, adiabatic positive ions, & negatively charged stationary dust & vortex-like distributed electrons. In this paper, the nonlinear propagation of dust-ion acoustic (DIA) solitary waves in a magnetized dusty electronegative plasma with trapped electrons is investigated. Due to the presence of trapped electrons, the electron distribution function with the vortex-like distribution has been introduced. The stationary solution of the KdV equation (i.e. DIA solitons) in this plasma is found & the influence of different parameters on the amplitude & width of DIA solitons is investigated. In these regions, due to the presence of a high density of dust grains, different types of collective processes exist & very rich wave modes can be excited. One of these is low-frequency dust ion-acoustic (DIA) waves. Shukla & Silin have shown the existence of dust-ion-acoustic (DIA) waves in a dusty plasma containing boltzmann electrons, mobile ions, & negatively charged stationary dust theoretically.

Propagation and oblique collision of ion-acoustic solitary waves in a magnetized dusty electronegative plasma

The propagation and oblique collision of ion-acoustic (IA) solitary waves in a magnetized dusty electronegative plasma consisting of cold mobile positive ions, Boltzmann negative ions, Boltzmann electrons, and stationary positive/negative dust particles are studied. The extended Poincaré-Lighthill-Kuo perturbation method is employed to derive the Korteweg-de Vries equations and the corresponding expressions for the phase shifts after collision between two IA solitary waves. It turns out that the angle of collision, the temperature and density of negative ions, and the dust density of opposite polarity have reasonable effects on the phase shift. Clearly, the numerical results demonstrated that the IA solitary waves are delayed after the oblique collision. The current finding of this work is applicable in many plasma environments having negative ion species, such as D- and F-regions of the Earth's ionosphere and some laboratory plasma experiments.

Nonplanar waves with electronegative dusty plasma

A rigorous theoretical investigation has been made of basic characteristics of the nonplanar dust-ion-acoustic shock and solitary waves in electronegative dusty plasma containing Boltzmann electrons, Boltzmann negative ions, inertial positive ions, and charge fluctuating (negatively charged) stationary dust. The Burgers' and Korteweg–de Vries (K-dV) equations, which is derived by reductive perturbation technique, is numerically solved to examine the effects of nonplanar geometry on the basic features of the DIA shock and solitary waves formed in the electronegative dusty plasma. The implications of the results (obtained from this investigation) in space and laboratory experiments are briefly discussed.

Multidimensional instability of dust ion-acoustic solitary waves in a magnetized dusty electronegative plasma

AbstractBasic features of obliquely propagating dust ion-acoustic (DIA) solitary waves, and their multidimensional instability in a magnetized dusty electronegative plasma (DENP) containing Boltzmann electrons, Boltzmann negative ions, adiabatic mobile positive ions, and negatively charged stationary dust have been theoretically investigated by reductive perturbation method and small-k perturbation expansion technique. The combined effects of ion adiabaticity, external magnetic field (obliqueness), and negatively charged dust, which are found to significantly modify the basic properties (speed, amplitude, width, and instability) of small but finite-amplitude DIA solitary waves, are explicitly examined. It is also found that the instability criterion and the growth rate of unstable perturbation are significantly modified by the external magnetic field, the propagation directions of both the nonlinear waves, and their perturbation modes. The implications of our results in space and laboratory dusty plasmas are briefly discussed.

Dust-ion-acoustic shock and solitary waves in a dusty electronegative plasma

A dusty electronegative plasma containing Boltzmann electrons, Boltzmann negative ions, warm positive ions, and charge fluctuating (negatively charged) stationary dust has been considered. The basic features of the shock and solitary waves, which are associated with positive ion dynamics and dust charge fluctuation, have been investigated by employing the reductive perturbation method. It has been shown that the dust charge fluctuation is a source of dissipation, and is responsible for the formation of dust-ion-acoustic shock structures. The implications of the results (obtained from this investigation) in space and laboratory experiments have been discussed.

Dust ion-acoustic solitary waves in a magnetized dusty electronegative plasma

AbstractThe basic features of obliquely propagating dust ion-acoustic (DIA) solitary waves in an adiabatic magnetized dusty electronegative plasma (containing Boltzmann electrons, Boltzmann negative ions, adiabatic positive ions, and negatively charged stationary dust) have been investigated. The reductive perturbation method has been employed to derive the Korteweg–de Vries (KdV) equation which admits a solitary wave solution. The combined effects of ion adiabaticity and external magnetic field (obliqueness), which are found to significantly modify the basic features of the small but finite-amplitude DIA solitary waves, are explicitly examined. The implications of our results in space and laboratory dusty plasmas are briefly discussed.

Solitary waves and double layers in a dusty electronegative plasma

A dusty electronegative plasma containing Boltzmann electrons, Boltzmann negative ions, cold mobile positive ions, and negatively charged stationary dust has been considered. The basic features of arbitrary amplitude solitary waves (SWs) and double layers (DLs), which have been found to exist in such a dusty electronegative plasma, have been investigated by the pseudopotential method. The small amplitude limit has also been considered in order to study the small amplitude SWs and DLs analytically. It has been shown that under certain conditions, DLs do not exist, which is in good agreement with the experimental observations of Ghim and Hershkowitz [Y. Ghim (Kim) and N. Hershkowitz, Appl. Phys. Lett. 94, 151503 (2009)].