Propagation Of Dust-acoustic Waves Research Articles

Study of the Characteristics of Dust Acoustic Solitary Waves and Dust Acoustic Shock Waves in Electron Free Dusty Space Plasma

A theoretical investigation has been done for the study of dust acoustic solitary waves and dust acoustic shock waves propagating in an unmagnetized, collisionless Lorentzian dusty plasma considering adiabatic and non-adiabatic dust charge variation. Plasma under consideration is composed of inertialess Lorentzian positive and negative ions along with inertial positively charged dust grains. Such dust grains are charged by the flow of positive ion and negative ion current over the grain surface. Adiabatic grain charge variation shows the existence of compressive soliton whose amplitude decreases and width increases with increasing number of suprathermal particles. Non-adiabatic dust charge variation is concerned with the propagation of monotonic dust acoustic shock waves which do not loose monotonicity even when a number of suprathermal particles are very large.

Dust-acoustic shock waves in a dusty plasma with non-thermal ions and super-thermal electrons

The propagation of dust-acoustic shock waves (DASWs) in a collisionless unmagnetized dusty plasma (containing super-thermal electrons of two distinct temperatures, non-thermal ions, and a negatively charged viscous dust fluid) has been theoretically investigated by deriving and solving the nonlinear Burgers' equation. It has been observed that the viscous force acting on the dust fluid is a source of dissipation, and is responsible for the formation of DASWs, and that the basic features (viz., amplitude, polarity, width, etc.) of the DASWs are significantly modified by the presence of super-thermal electrons and non-thermal ions. The possible applications of this investigation in Earth's mesosphere, the solar atmosphere, Saturn's magnetosphere, etc., have also been briefly addressed.

Ion Nonthermality Induced Nonlinear Dust Acoustic Wave Propagation in a Complex Plasma in Presence of Weak Secondary Electron Emission from Dust Grains

In this paper we have investigated the effect of ion nonthermality on nonlinear dust acoustic wave propagation in a complex plasma in presence of weak secondary electron emission from dust grains. Equilibrium dust charge in this case is negative. Dusty plasma under our consideration consists of inertialess nonthermal ions, Boltzman distributed primary and secondary electrons and negatively charged inertial dust grains. Both adiabatic and nonadiabatic dust charge variations have been taken into account. Our analysis shows that in case of adiabatic dust charge variation, at a fixed non-zero ion nonthermality increasing secondary electron emission decreases amplitude and increases width of the rarefied dust acoustic soliton whereas for a fixed secondary electron yield increasing ion nonthermality increases amplitude and decreases width of such rarefied dust acoustic soliton. Thus shape of the soliton may be retained if strength of both the secondary electron yield and the ion nonthermality are increased. Nonadiabatic dust charge variation shows that, at fixed non-zero ion nonthermality, increasing secondary electron emission suppresses oscillation of oscillatory dust acoustic shock at weak nonadiabaticity and pronounces monotonicity of monotonic dust acoustic shock at strong nonadiabaticity. On the other hand at a fixed value of the secondary electron yield, increasing ion nonthermality enhances oscillation of oscillatory dust acoustic shock at weak nonadiabaticity and reduces monotonicity of monotonic dust acoustic shock at strong nonadiabaticity. Thus nature of dust acoustic shock may also remain unchanged if both secondary electron yield and ion nonthermality are increased.

Effect of secondary electron emission on nonlinear dust acoustic wave propagation in a complex plasma with positive equilibrium dust charge

In this paper, we have investigated the effect of secondary electron emission on nonlinear propagation of dust acoustic waves in a complex plasma considering equilibrium dust charge positive and compared the results with those obtained in our recently published paper [Bhakta et al., Phys. Plasmas 24, 023704 (2017)] where the equilibrium dust charge was negative. In both papers, primary and secondary electrons are assumed to follow Boltzmann distribution with separate electron temperatures, ions are also Boltzmann distributed, and charged dust grains are inertial. Change in the nature of dust charge (negative to positive) gives rise to some opposite behaviour of wave propagation characteristics in dusty plasma when dust grains are charged by secondary electron emission mechanism. Both adiabatic and nonadiabatic dust charge variations have been separately considered in both the papers. The investigation in this paper shows that compressive dust acoustic soliton propagates in case of adiabatic dust charge variation whose amplitude increases and width decreases with an increase in the strength of the secondary electron emission. This is in contrast to the case of negative equilibrium dust charge which confirms the existence of rarefied dust acoustic soliton with decreasing amplitude and increasing width for an increase in the strength of the secondary electron emission. Nonadiabaticity of dust charge variation in both cases generates dust acoustic shock wave which is oscillatory for weak nonadiabaticity and monotonic for strong nonadiabaticity. For positive equilibrium dust charge, the amplitude of both oscillatory and monotonic shocks increases and oscillation of the oscillatory shock persists longer for stronger secondary electron emission. On the other hand for negative equilibrium dust charge, the amplitude of both the oscillatory and monotonic shocks diminishes with increasing secondary electron emission.

Effect of ion nonthermality on nonlinear dust acoustic wave propagation in a complex plasma in presence of secondary electron emission

In this paper we have investigated the effect of ion nonthermality on nonlinear dust acoustic wave propagation in a complex plasma in presence of secondary electron emission considering equilibrium dust charge positive. In space and astrophysical plasmas presence of nonthermal ions have been detected by satellite observations. This ion nonthermality modifies propagation characteristics of dust acoustic waves when dust grains are charged by secondary electron emission mechanism. In case of dust charging by secondary electron emission process two stable equilibrium dust charge states exist out of which one is negative and the other is positive. Here we have considered positive equilibrium dust charge state and both adiabatic and nonadiabatic dust charge variation. Our investigation shows that characteristics of both dust acoustic soliton and dust acoustic shock depend on the strength of the ion nonthermality along with secondary electron yield. Increase in both ion nonthermality and secondary electron yield help to retain the shape of compressive dust acoustic soliton when dust charge variation is adiabatic and to maintain oscillation of the dust acoustic shock when dust charge variation is nonadiabatic.

Higher order nonlinear dust-acoustic waves in a dusty plasma with dust of opposite polarity

The nonlinear propagation of dust-acoustic (DA) waves in an unmagnetized dusty plasma (containing positive and negatively charged inertial dust grains and nonextensive distributed electrons and ions) have been investigated theoretically. Three different types of nonlinear dynamical equations, namely, Korteweg-de Vries (K-dV), modified K-dV (mK-dV) and Gardner equations have been derived by employing the reductive perturbation method. The basic features (viz., polarity, amplitude, width, etc.) of solitary waves have been also analyzed numerically. It has been observed that the effects of nonextensivity of electrons and ions, mass and charge of positive and negative dust, and different dusty plasma parameters have significantly modified the fundamental properties of the solitary waves.

Characteristics of dust acoustic waves in dissipative dusty plasma in the presence of trapped electrons

The formation and propagation of nonlinear dust acoustic waves (DAWs) as solitary and solitary/shock waves in an unmagnetized, homogeneous, dissipative and collisionless dusty plasma comprising negatively charged micron sized dust grains in the presence of free and trapped electrons with singly charged non-thermal positive ions is discussed in detail. The evolution characteristics of the solitary and shock waves are studied by deriving a modified Korteweg–de Vries–Burgers (mKdV–Burgers) equation using the reductive perturbation method. The mKdV–Burgers equation is solved considering the presence (absence) of dissipation. In the absence of dissipation the system admits a solitary wave solution, whereas in the presence of dissipation the system admits shock waves (both monotonic and oscillatory) as well as a combination of solitary and shock wave solutions. Standard methods of solving the evolution equation of shock (solitary) waves are used. The results are discussed numerically using standard values of plasma parameters. The findings may be useful for better understanding of formation and propagation of waves in astrophysical plasma.

Dust-Acoustic Solitons in a Polarized Dusty Plasma With Nonthermal Ions

We theoretically investigate the effects of the nonthermal polarization force acting on dust grains in an inhomogeneous plasma containing Maxwellian electrons, nonthermal ions, and fluid negatively charged dust grains. The effects of this polarization force are significantly modified due to the presence of the nonthermal ions. In particular, an increase of the relative fraction of the nonthermal ions leads to a decrease of the polarization parameter. The modifications arising in the propagation of weak dust-acoustic (DA) solitary waves due to the presence of this nonthermal polarization force are then analyzed. As the magnitude of the polarization force increases, the energy carried by the DA soliton experiences a depletion.

Propagation of dust acoustic solitary waves in inhomogeneous plasma with dust charge fluctuations

Propagations of dust acoustic solitary waves are theoretically investigated in a collisionless, unmagnetized weakly inhomogeneous plasma. The plasma that is considered here consists of negatively charged dust grains and Boltzmann distributed electrons and ions in the presence of dust charge fluctuations. The fluid equations that we use for description of such plasmas are reduced to a modified Korteweg–de-Vries equation by employing a reductive perturbation method. In this investigation, we have used space–time stretched coordinates appropriate for the inhomogeneous plasmas. From the numerical results, we have observed a significant influence of inhomogeneity parameters on the propagation of dust acoustic solitary waves.

Effect of secondary electron emission on nonlinear dust acoustic wave propagation in a complex plasma with negative equilibrium dust charge

In this paper, we have investigated the effect of secondary electron emission on nonlinear propagation of dust acoustic waves in a complex plasma where equilibrium dust charge is negative. The primary electrons, secondary electrons, and ions are Boltzmann distributed, and only dust grains are inertial. Electron-neutral and ion-neutral collisions have been neglected with the assumption that electron and ion mean free paths are very large compared to the plasma Debye length. Both adiabatic and nonadiabatic dust charge variations have been separately taken into account. In the case of adiabatic dust charge variation, nonlinear propagation of dust acoustic waves is governed by the KdV (Korteweg-de Vries) equation, whereas for nonadiabatic dust charge variation, it is governed by the KdV-Burger equation. The solution of the KdV equation gives a dust acoustic soliton, whose amplitude and width depend on the secondary electron yield. Similarly, the KdV-Burger equation provides a dust acoustic shock wave. This dust acoustic shock wave may be monotonic or oscillatory in nature depending on the fact that whether it is dissipation dominated or dispersion dominated. Our analysis shows that secondary electron emission increases nonadiabaticity induced dissipation and consequently increases the monotonicity of the dust acoustic shock wave. Such a dust acoustic shock wave may accelerate charge particles and cause bremsstrahlung radiation in space plasmas whose physical process may be affected by secondary electron emission from dust grains. The effect of the secondary electron emission on the stability of the equilibrium points of the KdV-Burger equation has also been investigated. This equation has two equilibrium points. The trivial equilibrium point with zero potential is a saddle and hence unstable in nature. The nontrivial equilibrium point with constant nonzero potential is a stable node up to a critical value of the wave velocity and a stable focus above it. This critical value increases with increasing secondary electron emission. Thus, in the presence of secondary electron emission, higher velocity shock waves are monotonic. The results have been numerically explained considering the presence of Al2O3 dust grains in the plasma.

Characteristics of nonlinear dust acoustic waves in a Lorentzian dusty plasma with effect of adiabatic and nonadiabatic grain charge fluctuation

In this paper, characteristics of small amplitude nonlinear dust acoustic wave have been investigated in a unmagnetized, collisionless, Lorentzian dusty plasma where electrons and ions are inertialess and modeled by generalized Lorentzian Kappa distribution. Dust grains are inertial and equilibrium dust charge is negative. Both adiabatic and nonadiabatic fluctuation of charges on dust grains have been taken under consideration. For adiabatic dust charge variation reductive perturbation analysis gives rise to a KdV equation that governs the nonlinear propagation of dust acoustic waves having soliton solutions. For nonadiabatic dust charge variation nonlinear propagation of dust acoustic wave obeys KdV-Burger equation and gives rise to dust acoustic shock waves. Numerical estimation for adiabatic grain charge variation shows the existence of rarefied soliton whose amplitude and width varies with grain charges. Amplitude and width of the soliton have been plotted for different electron Kappa indices keeping ion velocity distribution Maxwellian. For non adiabatic dust charge variation, ratio of the coefficients of Burger term and dispersion term have been plotted against charge fluctuation for different kappa indices. All these results approach to the results of Maxwellian plasma if both electron and ion kappa tends to infinity.

Generalized polarization force acting on dust grains in a dusty plasma

Abstract The polarization force acting on dust particles in a dusty plasma is revisited within the theoretical framework of the Tsallis statistical mechanics. The generalized nonextensive polarization force expression is derived. As application, the modifications arising in the propagation of dust-acoustic solitary waves, and dust sheath formation are analyzed. Our results should be of wide relevance to explain and interpret the sheath formation and its structure in nonequilibrium plasmas related process such as surface treatments and ion implantation.

Backward dust-acoustic waves

This paper studies the peculiarities of Dust-acoustic wave (DAW) propagation in a plasma with a moving dusty flow. As a result of a dispersion relation analysis, it is shown that at definite conditions, the DAWs can exist in the form of backward waves with antiparallel group and phase velocities. The range of the dusty flow velocities is found for the backward DAW realization.

Generalized polarization force acting on charge fluctuating dust grains and its effects on propagation of dust-acoustic waves in a dusty plasma

The generalized expression for the polarization force (which mainly arises due to the polarization of plasma ions around the dust grains) acting on charge fluctuating dust grains has been derived. The effect of such generalized polarization force on the propagation of the dust-acoustic waves in such dusty plasma has been also examined. It has been found that both the real and imaginary parts of the dust-acoustic wave frequency are significantly modified by this generalized polarization force. The implications of our results in some real situations of space and laboratory dusty plasmas are briefly discussed.

Nonlinear Dust Acoustic Waves in Strongly Coupled Dusty Plasmas with Positively Charged Dust Particles**Supported by National Natural Science Foundation of China under Grant No. 11104012, the Fundamental Research Funds for the Central Universities under Grant Nos. FRF-TP-09-019A and FRF-BR-11-031B

The nonlinear propagation of dust acoustic waves is investigated in four-component plasmas consisting of positively charged dust grains, trapped ions, nonthermal electrons, and photoelectron due to ultraviolet irradiation. We use generalized viscoelastic hydrodynamic model for strongly coupled dust grain. In the weak nonlinearity limit, a modified Kadomstev–Petviashvili (KP) equation and a modified KP-Burger equation, which have a damping term coming from nonadiabatic charge variation, have been derived in the kinetic regime and hydrodynamic regime, respectively. With the increasing of UV photon flux, the hydrodynamic regime changes to kinetic regime. The approximate analytical line soliton and shock solutions are investigated in the kinetic regime and hydrodynamic regime, respectively.

Effect of Electron and/or Ion Nonthermality on Dust Acoustic Wave Propagation in a Complex Plasma in Presence of Positively Charged Dust Grains Generated by Secondary Electron Emission Process

In this paper we have developed a model to study the role of both electron and ion nonthermalities on dust acoustic wave propagation in a complex plasma in presence of positively charged dust grains. Secondary electron emission from dust grains has been considered as the source of positive dust charging. As secondary emission current depends on the flux of primary electrons, nonthermality of primary electrons changes the expression of secondary emission current from that of earlier work where primary electrons were thermal. Expression of nonthermal electron current flowing to the positively charged dust grains and consequently the expression of secondary electron current flowing out of the dust grains have been first time calculated in this paper, whereas the expression for nonthermal ion current flowing to the positively charged dust grains is present in existing literature. Dispersion relation of dust acoustic wave has been derived. From this dispersion relation real frequency and growth rate of the wave have been calculated. Results have been plotted for different strength of nonthermalities of electrons and ions.

Stability of three-dimensional obliquely propagating dust acoustic waves in dusty plasma including the polarization force effect

Propagation of dust acoustic solitary waves (DASWs) in a magnetized dusty plasma consisting of extremely massive, negatively/positively charged dust fluid and Boltzmann distributed electrons and ions is studied. A nonlinear Zakharov-Kuznetsov (ZK) equation adequate for describing the solitary waves is derived by applying a reductive perturbation technique. Moreover, an extended Zakharov Kuznetsov (EZK) equation is derived at the vicinity of the critical phase velocity. The effects of the polarization force are explicitly discussed and the growth rate of the produced waves is calculated. It is found that the physical parameters have strong effects on the instability criterion as well as on the growth rate. It is noted that the phase velocity decreases as the polarization force, the effective-to-ion temperature ratio, and the ion-to-electron temperature ratio increase. Moreover, the nonlinearity coefficient and the critical phase velocity increase by increasing the polarization force. The relevance of these findings to a recent plasma experiment and astrophysical plasma observations is briefly discussed.

Nonplanar dynamics of variable size dust grains in nonextensive dusty plasma

The nonplanar propagation of variable size dust grains in an unmagnetized, collisionless nonplanar (cylindrical) dusty plasma is investigated. The plasma is composed of cold positive and negative dust fluids and nonextensively distributed ions and electrons. The dust size distribution (DSD) is proposed to obey a power law distribution function which is widely applicable in space plasmas. The reductive perturbation technique is employed, and a cylindrical Kadomtsev-Petviashvili equation, describing the nonlinear propagation of dust acoustic waves (DAWs), is obtained. New solutions of this evolution equation (hyperbolic, trigeometrical, and rational) are obtained using G′/G-expansion method. In addition, the proposed model permits the two soliton types, i.e., the rarefactive and compressive solitons. It is found that the DSD and nonextensive distributions have drastic effects on the basic properties of the nonlinear cylindrical DAWs; the phase velocity, the amplitude, and the width. The applications of the present findings in certain astrophysics environments (such as Jupiter's magnetosphere and Earth's mesosphere), where both of the DSD and the geometrical effects are important, are discussed.

The nonadiabatic dust charge variation on dust acoustic solitary and shock waves in strongly coupled dusty plasmas

The combined effects of nonadiabatic dust charge fluctuation and strongly coupled dust particles on the nonlinear propagation of dust acoustic (DA) waves in dusty plasma consisting of nonthermal electrons and trapped ions with vortex-like distribution are presented here. We use generalized viscoelastic hydrodynamic model for dust particles. In the weak nonlinearity limit, a modified Korteweg–de Vries (KdV) equation with a damping term and a KdV–Burger equation have been derived in the kinetic regime and hydrodynamic regime, respectively. The approximate analytical solitary solution of modified KdV equation is derived in the weak nonadiabatic dust charge variation limit, which shows that the amplitude of DA solitary waves decreases with time. The presence of viscosity due to strong coupling stands for the formation of DA shock waves in the hydrodynamic regime. The results show that the DA shock waves will be oscillating one for weak viscosity and will become monotonic ones for large viscosity.

Dust acoustic shock waves in arbitrarily charged dusty plasma with low and high temperature non-thermal ions

Using the well-known reductive perturbation technique, the three-dimensional (3D) Burgers equation and modified 3D Burgers equation have been derived for a plasma system comprising of non-thermal ions, Maxwellian electrons, and negatively charged fluctuating dust particles. The salient features of nonlinear propagation of shock waves in such plasmas have been investigated in detail. The different temperature non-thermal ions and Maxwellian electrons are found to play an important role in the shock waves solution. The analytical solution of the 3D Burgers equation and modified 3D Burgers equation ratifying the propagation of dust acoustic shock waves are derived using the well-known tanh method. On increasing the population of non-thermal ions, an enhancement in the amplitude of shock waves is seen for negatively charged dust particles. A striking dependence of amplitude and width of shock waves on the ratio of ion temperatures and densities are also reported. Finally we introduced a new stretching coordinate and perturbation for the nth-order nonlinear 3D Burgers equation and its solution by the use of the tanh method. We found that, due to higher nonlinearity, the amplitude of shock waves decreases while width remains constant for all plasma parameters considered in the present investigation. The features accounted here could be relevant in the case of different space and astrophysical plasmas and laboratory dusty plasma for negatively charged dust fluctuation.