Dust Charge Relaxation Research Articles

Langmuir wave in a dusty plasma with nonextensive electrons

The effect of the dust charge perturbation on Langmuir waves in a dusty plasma with nonextensive electrons and Maxwellian ions is investigated within the fluid theory framework, where the sink term of electrons in the continuity equation is considered. The dispersion of Langmuir waves shows that the dust charge relaxation introduces an additional source of dissipation in Langmuir waves. The damping rate of Langmuir oscillation caused by the dust charge fluctuations is bigger than the one with Maxwellian electrons when the nonextensively distributed electrons have a suprathermal tail. On the contrary, the excess of low energy electrons for nonextensively distributed electrons can lower the damping rate of Langmuir oscillation. These differences are mainly due to the modification of the unperturbed electron attachment frequency by the nonextensively distributed electrons. Our results may be of wide relevance to space and interstellar plasmas.

Potential distribution around a test charge in a positive dust-electron plasma

The electrostatic potential caused by a test-charge particle in a positive dust-electron plasma is studied, accounting for the dust-charge fluctuations associated with ultraviolet photoelectron and thermionic emissions. For this purpose, the set of Vlasov–Poisson equations coupled with the dust charging equation is solved by using the space–time Fourier transform technique. As a consequence, a modified dielectric response function is obtained for dust-acoustic waves in a positive dust-electron plasma. By imposing certain conditions on the velocity of the test charge, the electrostatic potential is decomposed into the Debye–H¨uckel (DH), wake-field (WF), and far-field (FF) potentials that are significantly modified in the limit of a large dust-charge relaxation rate both analytically and numerically. The results can be helpful for understanding dust crystallization/coagulation in twocomponent plasmas, where positively charged dust grains are present.

Electron–ion attachment induced instability of dust acoustic waves in the presence of ionization in a charge varying collisional dusty plasma

Low frequency electrostatic dust acoustic wave (DAW) instability with a significant background pressure of neutrals has been investigated in a collisional dusty plasma incorporating the dust charge relaxation and electron–ion attachment (recombination) onto dust grains using a self consistent theory. A long wavelength mode is found to be unstable due to electron–ion attachment on to the dust grains. Applications to experimental observations of low frequency fluctuation and the relevance of these results to ‘void’ in a laboratory gas discharge dusty plasma are briefly discussed.

Electrostatic acoustic modes in a self-gravitating complex plasma with variable charge impurities

A linear theory of dust acoustic (DA) and dust ion-acoustic (DIA) waves in a self-gravitating collisional dusty plasma contaminated by variable-charge impurities is presented for a self-consistent closed system. The ion-drag force arising from the ion orbital motion as well as momentum transfer from all the ions and self-gravitation are taken into consideration. The physical processes, viz., dust-charge relaxation, ionization, recombination and collisional dissipations are also taken into account self-consistently. The generalized dispersion relation describing the coupling of the acoustic modes with the dust-charge relaxation mode (CRM) and damping of the waves is derived and analyzed numerically.

Effects of dust-charge fluctuations on the potential of an array of projectiles in a partially ionized dusty plasma

The expressions for the Debye and the wake potential are derived by incorporating dust-charge fluctuations of a single projectile, as well as of an array of dust grain projectiles, propagating through a partially ionized dusty plasma with a constant velocity. Numerically, the effects of the dust-charge fluctuations and the dust–neutral collisions on the electrostatic potential for a single, three, six and ten projectiles are examined. The dust-charge relaxation rate modifies the shape of the Debye as well as the wake potential. For smaller values of the relaxation rates a potential well is formed instead of Debye potential.

Ion-acoustic waves in a complex plasma with negative ions.

A self-consistent theory of linear waves in complex laboratory plasmas containing dust grains and negative ions is presented. A comprehensive model for such plasmas including source and sink effects associated with the presence of dust grains and negative ions is introduced. The stationary state of the plasma as well as the dispersion and damping characteristics of the waves are investigated. All relevant processes, such as ionization, diffusion, electron attachment, negative-positive ion recombination, dust charge relaxation, and dissipation due to electron and ion elastic collisions with neutrals and dust particles, as well as charging collisions with the dusts, are taken into consideration.

Modulational instability of short-wavelength ion waves in strongly coupled dusty plasmas.

Modulational instability of electrostatic short-wavelength ion waves in plasmas containing strongly coupled dusts with variable charge is considered. The evolution equations for the ion waves modulated by slow dust motion are obtained. The instability behavior differs considerably from that of plasmas with weakly coupled dust grains and depends strongly on the Coulomb coupling parameter as well as the dust-charge relaxation rate.

Electron density perturbations by electrostatic wavesand their effect on plasma waves in a dusty plasma

Interaction of high-frequency electrostatic waves and a staticelectron density perturbation is considered in a dusty plasmaincluding the effect of dusty charging. The static electrondensity perturbation is created by the low-frequencyponderomotive force in the parameter regime of a dusty plasmawhere the electron Debye length and temperature are much greaterthan the ion Debye length and temperature, respectively. Theelectron momentum damping rate (νe) due to the high-frequencycharging process of the dust grains can be much greateror much smaller than the electron plasma frequency or wavefrequency (ω) under consideration, depending upon theparameters of the dusty plasma.When ω>>νe, the nonlinear high-frequency wave coupledwith the electron density perturbation is described by anonlinear Schrödinger equation, which bears a modulationallyunstable envelope. When ω<<νe, the high-frequencyelectrostatic wave reduces to a dust charge relaxation mode andthe coupled nonlinear wave equation yields a solution of envelopeshocks.

On equilibrium states and dust charging in dusty plasmas

The dust-charge variation process is revisited, accounting for the background density variation associated with electron capture and release by the dust grains. It appears possible to maintain overall charge neutrality in the plasma without any external particle source or sink. It is shown that if the dust charge and density are sufficiently high, the effect of the background electron density variation on dust-charge relaxation is important. The equilibrium dust charge and its rate of variation are obtained for dusty plasmas subject to strong UV irradiation. The latter releases photoelectrons from the dust surface and can significantly affect the equilibrium dust charge, its variation rate, as well as the overall charge neutrality in the plasma.

Low-frequency electrostatic instabilities in strongly coupled dusty plasmas

Low-frequency electrostatic dust-wave instabilities in a plasma containing strongly correlated dust grains and ion flow are investigated. The effects of dust charge relaxation and strong Coulomb coupling are shown to be important in determining the instability behavior. The frequency and growth/damping rates of the waves exhibit transition behavior in the parameter space.

Dust-Acoustic Waves in Strongly Coupled Dusty Plasmas Containing Variable-Charge Impurities

A relatively self-consistent theory of dust-acoustic waves in the strongly coupled dusty plasmas containing variable-charge impurities is given. Relevant physical processes such as dust elastic relaxation and dust charge relaxation are taken into account. It is shown that the negative dispersion of dust-acoustic waves due to the strong correlation of dusts is enhanced in the presence of dust-neutral collisions.

Low-frequency dispersion properties of plasmas with variable-charge impurities

A theory of low-frequency dust-acoustic waves in low-temperature collisional plasmas containing variable-charge impurities is presented. Physical processes such as dust-charge relaxation, ionization-recombination of the electrons and ions, electron and ion elastic collisions with neutrals and dusts, as well as charging collisions with the dusts, are taken into account. Inclusion of these processes allows a balance of the plasma particles and thus a self-consistent determination of the stationary state of the unperturbed plasma. The generalized dispersion relation describing the propagation and damping of the dust acoustic waves is derived and analyzed.

Ion-acoustic waves in a dust-contaminated plasma.

A self-consistent theory of ion-acoustic waves in dusty gas discharge plasmas is presented. The plasma is contaminated by fine dust particles with variable charge. The stationary state of the plasma and the dispersion and damping characteristics of the waves are investigated accounting for ionization, recombination, dust charge relaxation, and dissipation due to electron and ion elastic collisions with neutrals and dusts, as well as charging collisions with the dusts.

Energy Loss of a Test Charge in Dusty Plasmas: Collective and Individual Particle Contributions

The energy loss of a test charge in dusty plasma with dust charge fluctuations has been calculated both analytically (within the frame work of dielectric theory) as well as numerically. The dust charge relaxation rate is found to have a significant effect on the total energy loss of a test charge which is the sum of collective response of the plasma and individual particle interaction. It is shown that the dust charge fluctuation enhances the energy loss due to the collective response of the plasma as well as the individual particle contributions. Further, the charge fluctuation converts the static Coulomb potential to a potential well for slow charge relaxation rates and a small test charge velocity. The test charge therefore gains energy instead of loosing. On the other hand for the large test charge velocity and fast charge relaxation rate, a shielded Debye Hückel type potential is formed and consequently the energy loss is enhanced. These results are useful for understanding coagulation of dust grains in space and laboratory plasmas.

High-Frequency Electrostatic Surface Oscillations in a Dust-Contaminated Plasma

High-frequency electrostatic surface waves at the interface of a dusty plasma and a dielectric wall are investigated. The effects of ionization, recombination, and dust-charge variation are taken into account in a self-consistent manner, so that the system considered is closed. It is shown that a coupling of the surface waves and the dust-charge relaxation mode leads to anomalous damping and frequency downshift of the waves.

Evolution of Langmuir waves in a plasma contaminated by variable-charge impurities

The propagation of Langmuir waves in nonisothermal plasmas contaminated by fine dust particles with variable charge is investigated for a self-consistent closed system. Dust charge relaxation, ionization, recombination, and collisional dissipation are taken into account. It is shown that the otherwise unstable coupling of the Langmuir and dust-charge relaxation modes becomes stable and the Langmuir waves are frequency down-shifted.

Langmuir wave instability in a dusty plasma.

By means of a self-consistent theory for dust charging, it is shown that the dust-charge relaxation process leads to an instability of the Langmuir waves.