Inhomogeneous Dusty Plasma Research Articles

Propagation of Ion-Acoustic Wave in an Inhomogeneous DustyPlasma with Dust Charge Fluctuation

The propagation of dust ion-acoustic wave in an inhomogeneous dustyplasma is studied by taking the dust charge fluctuation and collisionsinto account. It is shown that the dust charge fluctuation brings aphase shift to the wave. Furthermore, because of the presence of dustcharge fluctuation, a new damping term rises, which makes the dampingmore sharply.

Dust ion acoustic waves propagation in an inhomogeneous dusty plasma with positive and negative dust grains

The propagation of dust ion acoustic waves (DIAWs) in a collisionless, unmagnetized inhomogeneous dusty plasma containing cold positive ions, cold positive and negative dust grains, and isothermal electrons is theoretically studied. Nonlinear DIAWs are shown to be governed by a variable coefficient Kortewege–de Vries (KdV) equation. At the critical density of ions both compressive and rarefactive modified KdV solutions co-exist. Below (above) this critical point the system supports rarefactive (compressive) solitons.

Dust-acoustic solitary waves in an inhomogeneous magnetized hot dusty plasma with dust charge fluctuations

Using a standard reductive perturbation theory, a Zakharov-Kuznnetsov (ZK) equation is derived in an inhomogeneous dusty plasma comprised of negatively charged dust grains of equal radii, Boltzmann distributed electrons and positive ions. The effects of dust thermal pressure, dust charge variation, dust-neutral collision, and the external magnetic field are taken into account. Either compressive or rarefective solitons are shown to exist depending on the critical value of the phase velocity which in turn, depends on the dust temperature and pressure. An analytic soliton solution is obtained and discussed. The behaviors of the soliton amplitude, width, and the Mach number are investigated numerically for different plasma parameters.

Evolution of nonlinear dust-ion-acoustic waves in an inhomogeneous plasma

The propagation of nonlinear dust-ion-acoustic waves in an inhomogeneous dusty plasma is studied. At small but finite amplitudes, the wave evolution is governed by a modified Korteweg–deVries Burgers equation, whose coefficients are space dependent. The properties of the evolution equation are analyzed and the behavior of the corresponding shock and soliton solutions is numerically studied. If dust-charge perturbation is neglected, there exists a zero-nonlinearity point where the coefficient of the nonlinear term changes from negative to positive. At that point the nonlinear wave also undergoes structural deformation. If the dust-charge perturbation is taken into account, the zero-nonlinearity point may not appear and the soliton or shock wave will retain its form during the propagation.

Nonlinear waves in nonplanar and nonuniform dusty plasmas

The nonlinear properties of the dust acoustic solitary wave and shock wave in inhomogeneous nonplanar dusty plasmas are considered theoretically and numerically. The effects of nonthermally distributed ions, nonadiabatic dust charge fluctuation, and the inhomogeneity caused by nonuniform equilibrium particle density, nonuniform equilibrium charging, and nonplanar geometry on waves are presented. When τch∕τd is small but finite, where τch is the charging time scale and τd is the hydrodynamical time scale, a variable coefficients nonplanar Korteweg–de Vries (KdV) Burgers equation governing the nonlinear waves is derived by the perturbation method. The analytical expressions for the evolution of soliton and shock wave (both oscillatory and monotone shock) are obtained and the theoretical results are confirmed by the numerical solution of the nonlinear wave equation.

Dust-acoustic shock waves: Effect of plasma density gradient

The propagation of dust-acoustic shock waves in an inhomogeneous collisional dusty plasma is studied, where the equilibrium plasma densities and dust charges are spatially nonuniform but the dust density is uniform. It is shown that, in such a plasma, the dust charge density can change continuously from tenuous to dense state. The effect of collisions of the dust with neutral gas causes the damping of the amplitude, while collisionless dissipation arising from nonadiabatic dust charge variation results in the formation of the shock structure. The amplitude is proportional to the square root of the phase velocity of the linear dust-acoustic wave but inversely proportional to the square root of the equilibrium dust charge number, both of them vary with spatial positions. Due to the inhomogeneity, the relationships among the amplitude, the Mach number, and the width (rise time) of the shock front do not follow the simple monotonic behavior as in the homogeneous cases.

Non-linear waves in non-planar inhomogeneous dusty plasmas

Taking into account the inhomogeneity of the ion density and dust charging, the propagation of dust-ion acoustic solitary wave (DIASW) in a non-planar and inhomogeneous dusty plasmas is investigated analytically. The analytical expressions for the evolution of DIASW and the emitted radiation profiles of DIASW caused by the combined effects of non-planar geometry and inhomogeneity are obtained.

Dust–ion–acoustic soliton in an inhomogeneous collisional plasma

In inhomogeneous dusty plasmas, the ion–dust collisions are nonuniform because of the dependence of the collision rates on plasma densities and the grain charge. The propagation of dust–ion–acoustic solitons in such dusty plasmas is studied using the reductive perturbation method. It is shown that either compressive or rarefactive solitons can exist depending on whether the ion-to-electron density ratio is greater or less than a critical value. The interplay between the effects of the plasma inhomogeneity and the spatially varying collision rates can result in the amplitude distribution from decrease to increase when the soliton propagates from high to low density regions. Different from the homogeneous case, the velocity and width of the soliton increase with distance instead of following the changes of the amplitude.

Magnetic-curvature-driven interchange modes in dusty plasmas

The magnetic-curvature-driven interchange mode instability of a weakly inhomogeneous dusty plasma is rigorously investigated. It is shown that the electric drift convection of the equilibrium dust charge density is a stabilizing factor for long wavelength interchange modes. In a fully nonlinear regime, the finite amplitude interchange modes may self-organize in the form of a dipolar vortex. The present results should be useful in the understanding of the properties of the interchange mode turbulence in nonuniform magnetized plasmas containing charged dust particles.

Effect of ion–dust collisions on the propagation of ion acoustic wave in an inhomogeneous dusty plasma

Dust–ion-acoustic wave propagation in an inhomogeneous plasma is studied for the case of density-dependent ion–dust collisions. It is shown that, because of the interplay between the inhomogeneity and collisions, the relative amplitude of the wave first decreases and then increases with distance when the wave propagates down the density gradient.

Electrostatic waves in inhomogeneous dusty plasmas with grain charge fluctuation

The propagation of nonlinear dust-acoustic waves in inhomogeneous dusty plasmas consisting of electrons, ions, and charged dust particles is investigated. The grain charge fluctuation effect is also incorporated through the current balance equation. By using the perturbation method, a modified KdV equation governing the nonlinear behavior of the system is obtained. It has been shown that with the combined effects of dust number density inhomogeneous and the dust charge fluctuation would modify the wave structures. Amplitudes of the dust-acoustic waves decrease (increase) as the waves propagate in the direction of increasing (decreasing) dust number density.

Jeans instability of an inhomogeneous streaming dusty plasma

The dynamics of a self-gravitating unmagnetized, inhomogeneous, streaming dusty plasma is studied in the present work. The presence of the shear flow causes the coupling between gravitational and electrostatic forces. In the absence of self-gravity, the fluctuations in the plasma may grow at the expense of the density inhomogeneity and for certain wavelengths, such an unstable mode may dominate the usual streaming instability. However, in the presence of self-gravity, the plasma inhomogeneity causes an overlap between Jeans and streaming modes and collapse of the grain will continue at all wavelengths.

Self-excited motions in dusty plasmas with gradient of charge of macroparticles

Various self-excited motions in dusty plasmas involving spatial variations ofmacroparticle charge are considered. Two basic types of instabilities in thesesystems are examined numerically and analytically. The main attention isgiven to the vortex motions of macroparticles. Conditions suitable forcreating the instabilities examined are discussed. Experimental observationsof self-excited oscillations in dc-glow, and capacitive rf, discharges arepresented. It is shown that spatial variation of dust charge can account formany phenomena observed in inhomogeneous laboratory dusty plasmas.

The propagation of solitons in an inhomogeneous dusty plasma

The propagation of solitons in an inhomogeneous dusty plasma composed of two kinds of dust grains with different masses is investigated by using the reductive perturbation technique. In the lowest order, if the interface of the two kinds of dust grains is discontinuous, the transmission and reflection waves can be both described by the KdV equation. The numbers and amplitudes of both transimtted and reflected solitons from an incident soliton are given analytically for this case. If the interface of the two kinds of dust grains is continuous, neglecting the reflection, the nonlinear dust acoustic wave can be described by a KdV-type equation in the lowest order. The amplitudes, propagating velocities of these quasi-solitons for this case are also given analytically in this paper.

Collisionless reconnection of magnetic field lines in dusty plasmas

Stability of a thin current sheet in an inhomogeneous dusty plasma is investigated. A new mechanism for the collisionless reconnection of the magnetic field is found. It is associated with the linear instability of a surface shear-Alfvén mode which exists at the boundary between two plasma regions with different orientations of the sheared magnetic field. This new mode is possible only in dusty plasmas in which the electron and ion densities are inhomogeneous and different from each other. The dispersion properties of the surface mode are found to be strongly dependent on the spatial profile of the current sheet. The unstable linear mode is found in the case of a current sheet with steep edges. It is identified as the bending- (or kink-) mode, whose electrostatic and vector potentials, φ and Az, are symmetric and antisymmetric functions, respectively. In such a plasma configuration, the surface tearing mode (φ-antisymmetric, Az-symmetric) cannot propagate as an eigenmode. It arises only as a forced mode through the resonant coupling with the bending mode and the local convective cell. The increment of the bending/tearing instability is estimated from the second-order contribution of the resonance.

Steady State of the Dusty Plasma in a dc Discharge

The steady state formed by the diffusion of plasma particles inan inhomogeneous dusty plasma is investigatedtheoretically and compared with our previous experimental results [Nucl. Fusion Plasma Phys. 20(2000)180 (in Chinese); Phys. Plasmas8(2001)1459]. The negativelycharged dust grains with an average charge number of the order of105 on a single grain enhance theplasma inhomogeneity by decreasing the diffusion velocity,and can cause significant depletion of electrons.The theoreticalelectron density profile is in good agreement withthe experiment, and the theoretical profile ofthe electron-to-iondensity ratio is in reasonable agreement with experimentallyestimated data.

Self-excited motion of dust particles in a inhomogeneous plasma

Abstract Two novel types of instabilities in inhomogeneous dusty plasma are considered. It is shown that spatial dust charge variation provides an effective mechanism to excite the motion of particles. The results of experimental observation of various self-excited motions of dust particles in a dc-discharge plasma are presented. Conditions suitable for growing the considered instabilities in the dc-glow discharge are discussed.

Experimental observation of ion-acoustic waves in an inhomogeneous dusty plasma

The propagation of a dust-ion-acoustic wave (DIAW) wave down the steep density gradient in an inhomogeneous diffusive dusty plasma is experimentally studied. It is observed that the presence of the dust enhances the plasma inhomogeneity. The phase velocity of the DIAW increases rapidly with distance and becomes supersonic. The interplay between the effects of the density nonuniformity and collisional damping results in the continuous transition of the relative amplitude of the DIAW from damping to growth. The experimental data are in agreement with theoretical prediction and confirm the importance of density-dependent ion–dust collisions.

Crystallization in a Magnetized and Inhomogeneous Dusty Plasma with Streaming Ions

Possibility of existence of a drift-wave and its role on the dust-Coulomb crystal formation in an inhomogeneous, magnetized, and collisional dusty plasma with a continuous ion flow has been examined. It is noted that dust crystallization takes place predominantly in the inhomogeneous region of the dusty plasma with low magnetic field. The damping of the wake potential due to ion-neutral collisions restricts the formation of dust crystal within a few layers.

Effect of dust charge inhomogeneity on linear and nonlinear dust–acoustic wave propagation

Propagation of linear as well as nonlinear dust–acoustic waves (DAWs) in an inhomogeneous dusty plasma consisting of electrons, ions, and dust particles is investigated by taking into account equilibrium dust charge inhomogeneity along with the density inhomogeneity of the plasma and dust particles. For the linear case with harmonic perturbations, coupled equations for self-consistently determining the wave amplitude and the wave number have been derived. On the other hand, nonlinear DAWs are shown to be governed by a Korteweg–de Vries (KdV) type of evolution equation having variable coefficients arising due to charge and density inhomogeneities. Qualitatively, the amplitudes of the linear and nonlinear DAWs are found to decrease (increase) as the waves propagate into regions of increasing (decreasing) dust charge, which is similar to the behavior found in the case with density inhomogeneity alone. Quantitatively, the amplitude of the dust number density perturbation in the linear wave is proportional to qd0−3/2 nd0−1/2 for a cold dusty plasma, while in the nonlinear regime it scales as qd0−1 nd0−1/4. Approximate analytical solutions of the KdV equation have been obtained by making use of a suitable set of coordinate transformations.