Dust Charge Fluctuation Research Articles

Dust Acoustic Solitary Waves with Dust Charge Fluctuation in Superthermal Plasma

The nonlinear propagation of dust acoustic waves with dust charge fluctuation in presence of superthermal (kappa) electrons and ions has been investigated. Reductive perturbation technique along with space-time stretched coordinates is used to transform the basic nonlinear partial differential equations to a modified Korteweg-de-Vries equation. The modified Korteweg-de-Vries equation governs the dynamics of the small amplitude solitary waves in a superthermal dusty plasma. It is observed that the presence of kappa distributed electrons and ions significantly change the amplitude of solitons in an inhomogeneous environment. The present investigations may be useful to understand the nonlinear propagation of dust acoustic solitary waves in laboratory and space plasma.

Modified Jeans instability of collisional dusty magnetoplasma in presence of radiative cooling and dust charge fluctuation

We have investigated the modifications in the self-gravitational instability of magnetized collisional dusty plasma, arising from the radiative effects of electrons and ions, and charge fluctuation of dust. The electron and ion dynamics are described by their radiative effects and considering the full dynamics of dust and neutrals, the general dispersion relation is derived. The properties of the general dispersion relation are discussed in the absence and presence of dust charge fluctuation. The results of these two cases are further reduced for parallel and perpendicular modes of propagation. The consequences of magnetic field, collisions, dust charge fluctuation, and radiative condensation on the growth rate of self-gravitational instability are discussed analytically and graphically. We found that the radiative effects and dust charge variation increase the growth rate of self-gravitational instability while the presence of magnetic field and collisions shows the stabilizing behavior. The findings are discussed in context of the structure formation in interstellar clouds.

Effect of Electrostatic Interaction in the Formation of Dust-Acoustic Shock Wave with Fluctuating Dust Charge

A theoretical investigation on the effect of electrostatic interaction on dust acoustic wave (DAW) has been carried out in weakly nonlinear limit in strongly coupled regime with fluctuating dust charge. The generalized hydrodynamic set of equations is employed in the hydrodynamic limit. The dust−dust electrostatic interaction couples with dust charge fluctuation, as well as the viscosity of the medium, and provides the dissipative effect, which leads to the formation of shock wave in such a system. The novel feature of the present work is that, in the presence of charge fluctuation, the effective electrostatic temperature starts affecting the behavior and also enhancing the formation of monotonic shock wave. In this investigation, the dissipative effect arising due to charge fluctuation is dominant in comparison to the viscosity of the medium in the presence of electrostatic temperature.

On the nonlinear solitary and shock waves in Maxwellian multicomponent space plasma

Our objective is to study the nonlinear wave phenomena in a multicomponent plasma with Maxwellian electrons and ions. The main reason for this consideration is to exhibit the effects of dust charge fluctuations in plasma acoustic modes. Different aspects of nonlinear dynamics have been studied through the Korteweg-deVries (K-dV) equation (solitons) and the Burgers equation (shocks) derived by the reductive perturbation technique. A special method, known as the (G′/G) method, has been used for a solution. It predicts the different coherent features of various nonlinear waves successfully, and finally, their importance has been recognized in space plasmas. Evolutions have been shown with the input of appropriate typical plasma parameters to support our observations in space plasmas. All conclusions are in good agreement with the actual occurrences and could be of interest in furthering investigations in experiments and satellite observations in spaces. An important aspect of this exercise is a comparative study of K-dV and Burgers solutions in different plasma spaces.

Theoretical Modeling of an Ion-Beam-Driven Kelvin–Helmholtz Instability in a Plasma Cylinder Having Negatively Charged Dust Grains

An ion beam propagating through a magnetized plasma cylinder having negatively charged dust grains drives the Kelvin–Helmholtz instability (KHI) via Cerenkov interaction. The frequency and the growth rate of the KHI increase with the relative density of negatively charged dust grains $\delta $ . However, for large relative density of dust grains $\delta $ , the growth rate of KHI saturates. Moreover, beam density plays an important role in enhancing the growth rate of the KHI. It is also observed that finite boundary effects modify the dispersion properties of the KHI. The growth rate of KHI in a plasma cylinder is destabilized under the effect of dust charge fluctuations for relatively large velocity shears and low density of negatively charged dust grains $\delta $ . A comparative study of results is done for finite and infinite geometries of plasma waveguide.

New method for rekindling the nonlinear solitary waves in Maxwellian complex space plasma

Our interest is to study the nonlinear wave phenomena in complex plasma constituents with Maxwellian electrons and ions. The main reason for this consideration is to exhibit the effects of dust charge fluctuations on acoustic modes evaluated by the use of a new method. A special method (G′/G) has been developed to yield the coherent features of nonlinear waves augmented through the derivation of a Korteweg-de Vries equation and found successfully the different nature of solitons recognized in space plasmas. Evolutions have shown with the input of appropriate typical plasma parameters to support our theoretical observations in space plasmas. All conclusions are in good accordance with the actual occurrences and could be of interest to further the investigations in experiments and satellite observations in space. In this paper, we present not only the model that exhibited nonlinear solitary wave propagation but also a new mathematical method to the execution.

Characteristic Features of Double Layers in Rotating, Magnetized Plasma Contaminated with Dust Grains with Varying Charges

The evolution and the characteristic features of double layers in a plasma under slow rotation and contaminated with dust grains with varying charges under the effect of an external magnetic field are studied. The Coriolis force resulting from the slow rotation is responsible for the generation of an equivalent magnetic field. A comparatively new pseudopotential approach has been used to derive the small amplitude double layers. The effect of the relative electron-ion concentration, as well as the temperature ratio, on the formation of the double layers has also been investigated. The study reveals that compressive, as well as rarefactive, double layers can be made to co-exist in plasma by controlling the dust charge fluctuation effect supplemented by variations of the plasma constituents. The effectiveness of slow rotation in causing double layers to exist has also emanated from the study. The results obtained could be of interest because of their possible applications in both laboratories and space.

Dust-charge fluctuation effects on surface dust-acoustic waves in astrophysical half-space dusty plasmas

We investigate the dust-charge fluctuation effects on the propagation and the decay of the dust-acoustic surface plasma wave at the interface of plasma-vacuum in astrophysical half-space dusty plasmas. The dispersion relation for the surface mode is derived by using the appropriate plasma dielectric function. We found that wave frequency decreases as the dust-charging frequency increases as well as the dynamical wave number does. However, the damping rate of the surface wave increases with an increase of the dust-charging frequency and the dynamical wave number. Hence, the amplitude of the surface wave is found to be strongly suppressed with an increase of the dust-charging frequency. The increase of charging relaxation rate is found to suppress both of the real frequency of the wave and the damping rate of the surface wave in astrophysical half-space dusty plasmas.

Dust Ion-Acoustic Shock Waves in a Multicomponent Magnetorotating Plasma

Abstract The nonlinear properties of dust ion-acoustic (DIA) shock waves in a magnetorotating plasma consisting of inertial ions, nonextensive electrons and positrons, and immobile negatively charged dust are examined. The effects of dust charge fluctuations are not included in the present investigation, but the ion kinematic viscosity (collisions) is a source of dissipation, leading to the formation of stable shock structures. The Zakharov–Kuznetsov–Burgers (ZKB) equation is derived using the reductive perturbation technique, and from its solution the effects of different physical parameters, i.e. nonextensivity of electrons and positrons, kinematic viscosity, rotational frequency, and positron and dust concentrations, on the characteristics of shock waves are examined. It is observed that physical parameters play a very crucial role in the formation of DIA shocks. This study could be useful in understanding the electrostatic excitations in dusty plasmas in space (e.g. interstellar medium).

Role of Dust Grains in Beam-Driven Instabilities

The interaction of beam with magnetized plasma can lead to the excitation of many instabilities which are useful for understanding the stability, confinement and heating of the plasma. In the present work, we investigate the electromagnetic surface plasma waves, lower hybrid waves and ion cyclotron waves in three component dusty plasmas. The presence of charged dust grains modifies the dispersion relation of plasma waves. The charge and number density of dust grains and external magnetic field significantly modify the dispersion properties of these waves. It is shown that in the absence of beam, the plasma mode damps due to dust charge fluctuations and an additional damping dust charge fluctuation mode is induced in plasma. The beam propagating parallel or perpendicular to the magnetic field drives the plasma waves to instability via Cerenkov and cyclotron interaction. Using the analytical and numerical results the influence of the number density of negatively charged dust grains on growth rate of instabilities is studied.

Anomalous diffusion due to the non-Markovian process of the dust particle velocity in complex plasmas

In this work, the motion of a dust particle under the influence of the random force due to dust charge fluctuations is considered as a non-Markovian stochastic process. Memory effects in the velocity process of the dust particle are studied. A model is developed based on the fractional Langevin equation for the motion of the dust grain. The fluctuation–dissipation theorem for the dust grain is derived from this equation. The mean-square displacement and the velocity autocorrelation function of the dust particle are obtained in terms of the Mittag-Leffler functions. Their asymptotic behavior and the dust particle temperature due to charge fluctuations are studied in the long-time limit. As an interesting result, it is found that the presence of memory effects in the velocity process of the dust particle as a non-Markovian process can cause an anomalous diffusion in dusty plasmas. In this case, the velocity autocorrelation function of the dust particle has a power-law decay like t−α−2, where the exponent α take values 0<α<1.

Viscoelastic pulsational mode

We present a theoretical model analysis to study the linear pulsational mode dynamics in viscoelastic complex self-gravitating infinitely extended clouds in the presence of active frictional coupling and dust-charge fluctuations. The complex cloud consists of uniformly distributed lighter hot mutually thermalized electrons and ions, and heavier cold dust grains amid partial ionization in a homogeneous, quasi-neutral, hydrostatic equilibrium configuration. A normal mode analysis over the closed set of slightly perturbed cloud governing equations is employed to obtain a generalized dispersion relation (septic) of unique analytic construct on the plasma parameters. Two extreme cases of physical interest depending on the perturbation scaling, hydrodynamic limits and kinetic limits are considered. It is shown that the grain mass and viscoelastic relaxation time associated with the charged dust fluid play stabilizing roles to the fluctuations in the hydrodynamic regime. In contrast, however in the kinetic regime, the stabilizing effects are introduced by the dust mass, dust equilibrium density and equilibrium ionic population distribution. Besides, the oscillatory and propagatory features are illustrated numerically and interpreted in detail. The results are in good agreement with the previously reported findings as special corollaries in like situations. Finally, a focalized indication to new implications and applications of the outcomes in the astronomical context is foregrounded.

Self-Gravitational Instability of Collisional Dusty Plasma With Dust Charge Variation and Radiative Effects

The self-gravitational instability of partially ionized dusty plasma with radiative effects of electrons and ions, dust polarization force, and dust charge fluctuation has been studied. Using basic sets of fluid equations for ion, electron, neutral, and dust components, a general dispersion relation is derived. In the dynamics of dust charge, an equilibrium dust charge inhomogeneity along with the dust charge fluctuation is also considered. It is found that the presence of radiative cooling of ions and electrons, polarization force, and dust charge fluctuation significantly affects the criterion as well as the growth rate of self-gravitational instability while the dust charge inhomogeneity and dust-neutral collisions affect only the growth rate of instability. The outcomes of this paper are useful in dusty molecular clouds.

Memory effects in the velocity relaxation process of the dust particle in dusty plasma

In this paper, by comparing the timescales associated with the velocity relaxation and correlation time of the random force due to dust charge fluctuations, memory effects in the velocity relaxation of an isolated dust particle exposed to the random force due to dust charge fluctuations are considered, and the velocity relaxation process of the dust particle is considered as a non-Markovian stochastic process. Considering memory effects in the velocity relaxation process of the dust particle yields a retarded friction force, which is introduced by a memory kernel in the fractional Langevin equation. The fluctuation-dissipation theorem for the dust grain is derived from this equation. The mean-square displacement and the velocity autocorrelation function of the dust particle are obtained, and their asymptotic behavior, the dust particle temperature due to charge fluctuations, and the diffusion coefficient are studied in the long-time limit. As an interesting feature, it is found that by considering memory effects in the velocity relaxation process of the dust particle, fluctuating force on the dust particle can cause an anomalous diffusion in a dusty plasma. In this case, the mean-square displacement of the dust grain increases slower than linearly with time, and the velocity autocorrelation function decays as a power-law instead of the exponential decay. Finally, in the Markov limit, these results are in good agreement with those obtained from previous works on the Markov (memoryless) process of the velocity relaxation.

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.

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.

Lower order three-dimensional Burgers equation having non-Maxwellian ions in dusty plasmas

The dust acoustic (DA) shock wave with dust charge fluctuations, non-Maxwellian ions, and non-isothermal electrons is studied theoretically. The perturbation technique is employed to derive the lower order three-dimensional (3D) Burgers equation, and shock wave solution is explored by the tan-hyperbolic method. The effects of flat trapped and trapped electron distributions in the presence of Maxwellian and non-Maxwellian ions on characteristics shock waves are observed. The temperature ratio of non-Maxwellian ion temperature and non-isothermal electron temperature is found to play an important role in forming the shock-like structure.

Low frequency modes and instability analysis in non-thermal dusty magnetoplasma considering dust charge fluctuation and polarization force

The effect of non-thermal ion population on self-gravitational instability of magnetized dusty plasma considering electrons are in Maxwell-Boltzmann distribution has been investigated. The dust dynamics is described including polarization force, thermal velocity, and charge fluctuation dust. The modified general dispersion relation has been derived including non-thermal ion population, polarization force, and dust charge fluctuation for self-gravitating dusty plasma system, using the normal mode analysis method. The obtained general dispersion relation is discussed in parallel and perpendicular modes of propagation. The population of non-thermal ion, polarization force and dust charge fluctuation affect the self-gravitational instability criteria in both the modes of propagation while the magnetic field affects the instability criterion only in perpendicular mode of propagation. The domains of instability has been discussed analytically to signify the importance of considered parameters. The stability of the self-gravitating dusty plasma system has been analyzed using Routh-Hurwitz stability criterion. Numerical calculations have been performed to analyze the effects of non-thermal ion population, polarization force, and dust charge fluctuation on the growth rate of self-gravitational instability. The results of the present work can be useful in self-gravitating dusty plasma found in space and the interstellar medium such as the interstellar molecular clouds where non-thermally distributed ions are the species of the plasma matter.

Effect of ion radiative cooling on Jeans instability of partially ionized dusty plasma with dust charge fluctuation

In this paper, the effect of ion radiative cooling on the gravitational instability of dusty plasma is studied, incorporating dust charge fluctuation with dust-neutral, neutral-ion, and ion-neutral collisions. The basic equations are linearized using normal mode analysis to obtain a general dispersion relation. The general dispersion relation is analytically and numerically discussed to explain the role of ion radiative cooling in the structure formation through gravitational instability. The Jeans collapse criteria are found to be modified due to ion and electron radiative cooling, dust charge fluctuations, and collisions effects. It is determined from the analytical and numerical calculations that the support of radiative cooling of ions drives thermal fluctuations and gives instability to the system. The electron cooling effect remains dominating over ion cooling effect, and thus, it enhances the collapse more efficiently than ion cooling effect. Although the radiative cooling is slow, it may precede the collapse in molecular cloud, which further leads to the structure formation. The present work is relevance for the structure formation in the molecular cloud.

Temperature measurement of a dust particle in a RF plasma GEC reference cell

The thermal motion of a dust particle levitated in a plasma chamber is similar to that described by Brownian motion in many ways. The primary difference between a dust particle in a plasma system and a free Brownian particle is that in addition to the random collisions between the dust particle and the neutral gas atoms, there are electric field fluctuations, dust charge fluctuations, and correlated motions from the unwanted continuous signals originating within the plasma system itself. This last contribution does not include random motion and is therefore separable from the random motion in a ‘normal’ temperature measurement. In this paper, we discuss how to separate random and coherent motions of a dust particle confined in a glass box in a Gaseous Electronic Conference (GEC) radio-frequency (RF) reference cell employing experimentally determined dust particle fluctuation data analysed using the mean square displacement technique.