Dust Charge Fluctuation Research Articles

Pulsational mode dynamics in the presence of negions

The stability dynamics, of the gravito-electrostatically driven pulsational mode of gravitational collapse (PMGC) excitable in spherically symmetric dust molecular clouds (DMCs), is systematically theorized. It actively incorporates the interplay of dust viscosity, dust charge fluctuation dynamics, and negionic (negative ionic) effects. We take the DMC constitutive electrons, positive ions, and negions as the Boltzmann species (lighter). The negatively charged dust grains behave as viscous fluids (heavier). A generalized linear cubic dispersion equation, involving a new and unique set of multi-factorial dispersion coefficients, results from the applied spherical normal mode treatment in the DMC model. The diverse growth characteristics of the PMGC dynamics are investigated illustratively. It is found mainly that the cloud size, dust charge, equilibrium electronic number density, and equilibrium dust number density play stabilizing roles in the PMGC. However, the dust mass, equilibrium positive ionic number density, equilibrium negionic number density, and dust viscosity play destabilizing roles against self-gravity. The reliability of our study is ensured by the fact that the diversified stabilizing features explored here are consistent with the previous results. The applicability of our study in astrophysical gravity-driven structure formation processes moderated actively with the negionic effects is finally outlined.

Dust–ion–acoustic damped solitary waves and shocks in laboratory and Saturn's E-ring magnetized nonthermal dusty plasmas with anisotropic ion pressure and dust-charge fluctuation

We study the oblique propagation of weakly nonlinear dust–ion–acoustic (DIA) solitary waves (SWs) and shocks in collisional magnetized nonthermal dusty plasmas that are relevant in laboratory and space (Saturn's E-ring) environments. We consider plasmas to be composed of q-nonextensive hot electrons, thermal positive ions, and immobile negatively charged dust grains immersed in a static magnetic field and take into account the effects of ion creation (source), ion loss (sink), ion–neutral and ion–dust collisions, anisotropic ion pressure, and dust-charge fluctuations on the evolution of small-amplitude SWs and shocks. The ion–neutral collision enhancement equilibrium dust-charge number is self-consistently determined using Newton–Raphson method. We found that in laboratory dusty plasmas with adiabatic dust-charge variation [i.e., when the dust charging frequency (νch) is much higher than the dust–plasma oscillation frequency (ωpd)], the DIA solitary waves (DIASWs) get damped by the effects of the ion–dust and ion–neutral collisions, whereas the ion creation and ion loss lead to the amplification of solitary waves, and they appear as only compressive types with positive potential. On the other hand, in Saturn's E-ring plasmas, where the collisional and ion creation or ion loss effects are insignificant, the non-adiabaticity of dust-charge variation can give rise to the evolution of either damped DIASWs or DIA shocks, depending on the smallness of the ratios νch/ωpd or ωpd/νch, respectively. Furthermore, two critical values of the nonextensive parameter q exist, below (or above) which, the DIASWs and shocks can appear as rarefactive (or compressive) types. The characteristics of DIASWs and shocks are also analyzed numerically for parameters relevant to the laboratory and Saturn's E-ring plasmas.

Effects of dust size distribution and non-Maxwellian electrons on shock waves in a dusty plasma

We present a study of dust acoustic shock waves in a non-Maxwellian plasma with dust charge fluctuations, which are seen to cause a dissipation term in fluid model, and consequently shocks are generated. In particular, we focus on dust acoustic waves as affected by various dust size distributions. Two distinct dust size distributions—the polynomial and the power law distributions—have been used. For analytical investigation of nonlinear wave propagation in complex plasmas, a reductive perturbation approach is used to obtain the Burgers equation. A dusty plasma system with non-Maxwellian Kappa distribution is considered and it is shown that the amplitude of a shock wave, for the dust size distribution is larger than that for the mono-sized counterpart, while the shock width manifests an opposite trend. Furthermore, the shock wave speed is also affected by the dust size distributions as well as by the nature of velocity distribution function. To benchmark our findings, we apply the proper limit on the spectral index, i.e., κ→∞, and retrieve the Maxwellian results. The current findings are crucial for comprehending respective shock distributions for a plasma system exhibiting non-thermal characteristics and having dust size distributions.

Effect of dust size distribution and nonadiabatic charge variation on dispersion relation for linear waves in inhomogeneous complex plasmas

This paper explores linear waves’ instability in nonuniform complex plasmas with dust size distribution and non-adiabatic dust charge fluctuation. For this purpose, the dispersion relation is obtained with the aid of linearizing the hydrodynamic equations governing the properties of linear waves. The contribution of physical parameters such as inhomogeneity, nonadiabatic dust charge fluctuation, and dust size distribution to the features of dust acoustic waves is examined at great length. The numerical results show that the present research results are very important in the phenomenon of space astrophysical and experimental plasmas.

Dust acoustic shock waves in nonuniform dusty plasmas with kappa-distributed ions and electrons, nonadiabatic dust charge fluctuation and dust size distribution

Dust acoustic shock waves in nonuniform dusty plasmas with kappa-distributed ions and electrons, nonadiabatic dust charge fluctuation and dust size distribution

Analysis of dust charge fluctuations with double-ionized ions and plasma oscillations / instabilities in Hall thrusters

In an electric propulsion system such as thruster, dust particles are generated because of the thrusters' wall erosion, and these heavily charged dust particles affect the thrusters' performance and life span. In this article, the charge and potential of a dust grain for various dust and plasma parameters are analyzed in a Hall thruster plasma having high electron thermal energy in the presence of double-ionized ions. The charging time of the dust is shown to be reduced with the increase in size while the charge on it increases. This has been observed that the dust grains' charging time and floating potential decrease when the density of double-ionized ions is increased. An increment in the floating potential is observed for higher plasma potential and electron temperature, but this increment occurs slower for higher electron temperatures. The floating potential doesn't change with the size of the dust in the plasma with zero fluctuations, but it depends on the dust grain size for fluctuating plasma parameters and the frequency of these fluctuations.

Driven dust-charge fluctuation and chaotic ion dynamics in the plasma sheath and presheath regions.

Possible existence of chaotic oscillations in ion dynamics in the sheath and presheath regions of a dusty plasma, induced by externally driven dust-charge fluctuation, is presented in this work. In a complex plasma, dust charge fluctuation occurs continuously with time due to the variation of electron and ion currents flowing into the dust particles. In most of the works related to dust-charge fluctuation, theoretically it is assumed that the average dust-charge fluctuation follows the plasma perturbation, while in reality, the dust-charge fluctuation is a semirandom phenomenon, fluctuating about some average value. The very cause of dust-charge fluctuation in a dusty plasma also points to the fact that these fluctuations can be driven externally by changing electron and ion currents to the dust particles. With the help of a hybrid-particle in cell-Monte Carlo collision (h-PIC-MCC) code in this work, we use the plasma sheath as a candidate for driving the dust-charge fluctuation by periodically exposing the sheath-side wall to UV radiation, causing photoemission of electrons, which in turn drive the dust-charge fluctuation. We show that this driven dust-charge fluctuation can induce a chaotic response in the ion dynamics in the sheath and the presheath regions.

Dust-ion-acoustic shock waves in the presence of (r, q) distributed electrons

A three-component dusty plasma system, with non-Maxwellian electrons, is investigated. The ions are considered to be mobile, the (spherical) dust is assumed to be stationary with charge- fluctuations, and the electrons follow the generalized velocity distribution function (VDF). The respective Burger’s equation, which manifests a shock structure, is derived by employing a reductive perturbation technique (RPT). It is deduced that dust charge fluctuations induce shock potential in a collisionless plasma system. The resultant perturbed potential is evaluated as affected by different plasma parameters, e.g. the ratios of electron to ion temperature (σ i ) and equilibrium densities (μ), and the non-thermal indices r and q. The shock amplitude is seen to decrease when the value of σ i is increased, and vice versa, whereas an opposite trend is observed for μ. It is found that for r = 0 and increasing values of spectral index q, amplitude of the potential distribution enhances while its width decreases. It is further noted that non-Maxwellian VDF significantly modifies the potential distribution. For the limiting case, namely, r = 0 and q → ∞ , the corresponding Maxwellian results are retrieved which benchmarks our findings. Present work will be useful in understanding the nonlinear propagation of dust-ion-acoustic shock waves in system where non-thermal population—as caused by various physical processes—of electrons are observed.

Effect of charged dust grains on the electrojet instabilities

The Farley-Buneman and Gradient Drift instabilities have been investigated using a fluid model, in a partially ionized dusty electrojet region in which dust and neutral particles constitute a uniform static background. The effects of dissociative electron-ion recombination and dust charge fluctuation on the instabilities also have been taken into account. The electron-ion dynamics are considered to derive the perturbed densities which further lead to the generalized dispersion relation. The dispersion relation describes the propagation of electrojet instabilities having frequency within dust ion acoustic range in a magnetized partially ionized dusty plasma. The dispersion relation is separately solved numerically and analytically for the two values of anisotropy parameters which correspond to the two different altitudes in the electrojet region. It is found that Gradient drift instability is unstable at a much longer wavelength as compared to Farley-Buneman instability both with or without dust. At lower altitudes(90 km) the increase of negative charge on dust decreases the threshold electron drift velocity for Farley-Buneman instability while it shows the opposite behavior at higher altitudes(100 km). A much lower electron drift velocity is required to excite the Gradient drift instability than the Farley-Buneman instability at both altitudes. The dissociative electron-ion recombination damps both modes much more than the dust charge fluctuation. A significant changes in threshold drift velocity is observed for the Farley-Buneman mode as compared to the Gradient Drift mode due to the two main damping mechanisms. The present analysis is applicable in the lower ionospheric electrojet region where meteoric ablation processes are dominant.

Nonlinear Jeans-Buneman instability in gravitating complex plasmas

The nonlinear evolutionary dynamics of the hybrid Jeans-Buneman instability (JBI) in charge-fluctuating viscous dust molecular clouds (DMCs) of infinite extension is semi-analytically studied. The cloud macroscopic state is initially considered to be in a quasi-hydrostatic homogeneous equilibrium configuration, modeled in a classical non-relativistic framework, on the Jeans spatiotemporal scales. The global quasi-neutrality, dust-charge fluctuation, viscous dissipation, and inter-species collision effects are presumed to coexist. Such complex plasma situations are practically realizable in the star-forming DMCs in the diffused interstellar media extensively. A local nonlinear perturbative analysis herein yields a unique conjugational pair of coupled extended Korteweg-de Vries (e-KdV) equations on the gravito-electrostatic potential fluctuations. A numerical platform illustrates that the electrostatic and gravitational fluctuations grow as a unique admixture of compressive and rarefactive solitary wave patterns. It is seen that, even for cm-sized heavier dust grains, the gravitational wave amplitudes supersede the electrostatic counterparts. It is demonstrated geometrically that the electrostatic (gravitational) phase portraits are cyclically regular (irregular), unbounded (quasi-bounded), open (quasi-closed), and astable (quasi-stable) with no limit cycle behavior evolving as non(quasi)-homoclinic trajectories. The fluctuation amplitude-growth features with plasma multi-parametric variation is illustratively explored alongside its non-trivial futuristic applicability in bounded astrostructure formation.

Photoelectric effects on the instability of the current-driven dust ion-acoustic waves in a collisional and streaming dusty plasmas with dust charge fluctuation

Photoelectric effects on the instability of the current-driven dust ion-acoustic waves in a collisional and streaming dusty plasmas with dust charge fluctuation

Generation of an obliquely propagating shear alfven wave in dusty plasma by an ion beam

AbstractIon beam‐dusty plasma interaction leads to significant changes in the dispersion relation of shear Alfven wave depending on the beam, dust grain, and plasma parameters. Hydrogen ion beam particles interact with the shear Alfven wave via cyclotron interaction when they counter‐propagate with the wave and they can also interact with the co‐propagating wave via Cerenkov interaction. The interaction causes beam as well as plasma density fluctuations and gives rise to perpendicular currents. We have analytically obtained the dispersion relation and the growth/damping rate expressions for obliquely propagating shear Alfven waves in dusty plasma. The effect of beam velocity, magnetic field, wave number, dust particle density, and dust charge fluctuations are discussed. It is shown that both the wave frequency and the maximum growth rate decrease with an increase in beam velocity and the variations are different for parallel and perpendicular wave numbers. The dust particles enhance the frequency and maximum growth rate while the dust charge fluctuations induce damping. The results are in good agreement with the experimental observations.

Dust charge fluctuation and ion acoustic wave propagation in dusty plasma with q-nonextensive hot and Maxwellian cold electrons

We have employed the self-consistent kinetic theory to study the linear dispersion relation of ion acoustic waves in a four-component plasma consisting of nonextensive hot electrons, Maxwellian cold electrons, positive ions, and dust particles. The dust charging process with the modified ion acoustic wave damping, as well as its unstable mode, has been graphically illustrated. It is found that the dust charging mechanism depends on the density of hot electrons, the degree of nonextensive electron distribution, and the temperature ratio of hot to cold electrons. It is shown that the damping and instability rates of ion acoustic waves due to dust charge fluctuations explicitly depend on the choice of electron distribution and the magnitude of dusty plasma parameters. In addition, we have studied the ion acoustic Landau damping in the absence of dust particles. It is found that the weak damping region broadens, while the strong damping region shrinks and is shifted toward the short wavelength region for the increase in the temperature ratio of hot to cold electrons.

Obliquely propagating dust acoustic shock waves in magnetized plasma under the influence of polarization force and nonadiabaticity of dust charge variation

In this work, we have analyzed the impact of polarization force, angle of obliqueness under the influence of nonadiabatic dust charge fluctuation on shock waves formation in magneto rotating plasma. The present plasma model is consisting of negatively charged dust grains, Maxwellian electrons, non-Maxwellian hybrid distributed ions. The dissipation is introduced in the system via nonadiabaticity, a new mechanism for the formation of shock waves. Using the standard reductive perturbation method, nonlinear equation, namely, Korteweg-de Vries-Burgers (KdVB) equation is derived and solution is obtained using the Tanh method. It is shown that dust charge fluctuation is the main source of dissipation. We have studied the various parameteric influences on such shock structure and also showed how the gradual variations of these parameters affect the generation and structure of the shocks in their respective domain. Much of the experiments on dusty plasma with nonadiabatic dust charge fluctuation will benefit from the parametric study.

Effect of dust grains on the parametric coupling of a lower hybrid wave driven ion cyclotron wave in a tokamak plasma

In this article, the effect of dust charge fluctuations on the parametric upconversion of a lower hybrid wave into an ion cyclotron wave and a side band wave in a two-ion species tokamak plasma is studied. When the oscillatory velocity of plasma electrons is a few percent of the sound velocity, the lower hybrid wave becomes unstable and decays into two modes: an ion cyclotron wave mode and a low frequency lower hybrid side band wave. Furthermore, a ponderomotive force by a lower hybrid pump and a side band wave is exerted on the existing electrons, which drives the ion cyclotron decay mode. The presence of negatively charged dust grains and their shape, size, radius, and density influence the instability. The growth rate of instability is calculated by considering typical existing D–T (Deuterium–Tritium) dusty plasma parameters, and it is observed that the growth rate increases with the relative density of dust grains, number density of dust grains, oscillatory velocity of electrons, and amplitude of pump waves. However, the normalized growth rate increases with the unstable wave frequency, and it also increases as we increase the ratio of deuterium to tritium density. Here, the growth rate decreases with the increase in the size of dust grains and electron cyclotron frequency. The theoretical results summarized in the present study are able to efficiently elaborate the complexity produced in plasma properties in a tokamak due to the dust–plasma interactions, which are briefly discussed here.

Evolution of cylindrical/spherical shock formation in a dusty plasma with nonadiabatic dust charge variation

Cylindrical/spherical dust acoustic shock waves are studied in an unmagnetized plasma consisting of Maxwellian electrons, superthermal ions under the effect of nonadiabatic dust charge fluctuation. The dissipation is introduced in the system via nonadiabaticity, a new mechanism for the formation of shock waves. Using standard reductive perturbation method, nonplanar equation namely Korteweg–de Vries Burgers (KdVB) equation is derived and solution is obtained using the Weighted residual method. By use of weighted residual method, a progressive wave solution to nonplanar modified KdV Burgers equation is presented. It is shown that dust charge fluctuation produces dissipation which is responsible for shock formation. The solution shows that as one goes towards the axis of the cylinder or center of the sphere, the wave attenuates faster and the effects are shown in some 2D figures. We have studied various parametric influences on such shock structure and also showed how the gradual variations of these parameter affect the generation and structure of the shocks in their respective domain. Our results should be applicable to the formation of nonlinear DIA shock wave structures in regions in which dust grain is embedded in a Kappa distributed plasma, such as Saturn's magnetosphere.

Shock formation in magnetized plasma under the influence of polarization force and nonadiabaticity of dust charge variation

In this work, we have analyzed the impact of polarization force, angle of obliqueness under the influence of nonadiabatic dust charge fluctuation on shock waves formation in magneto rotating plasma. The present plasma model is consisting of negatively charged dust grains, Maxwellian electrons, nonextensive ions. The dissipation is introduced in the system via nonadiabaticity, a new mechanism for the formation of shock waves. Using standard reductive perturbation method, nonlinear equation namely Korteweg–de Vries Burgers equation is derived and solution is obtained using the Tanh method. It is shown that dust charge fluctuation is the main source of dissipation. We have studied the various parameteric influences on such shock structure and also showed how the gradual variations of these parameter affect the generation and structure of the shocks in their respective domain. Much of experiments on dusty plasma with nonadiabatic dust charge fluctuation will benefit from the parametric study.

Generation of ion cyclotron instability by parametric coupling of gyrating ion beam with lower hybrid wave in a complex plasma

In a two-ion species tokamak plasma, with the help of gyrating ion beam was to investigate the impact of dust charge fluctuations on the parametric up-conversion of lower hybrid wave (LHW) into an upper side band wave and an ion cyclotron wave. On the existing electrons, through an upper side band wave and lower hybrid pump, a ponderomotive force has been exerted which in turn drives the ion cyclotron decay mode. The growth rate of instability is calculated by considering typical existing D-T (Deuterium-Tritium) dusty plasma parameters and observed that with an increment in amplitude of pump waves, wave number of ion cyclotron mode, number density of dust grains and relative density of dust grains, an enhanced growth rate is reported. However, a reduction in the growth rate has been detected with enhancing dust grain size and electron cyclotron frequency. The findings of this work can play an imperative role in magnetized plasma sources used in plasma material interaction / surface processing. The tokamak operation is severely affected by the various sizes and density of dust grains, which in turn, considerably affect the choice of material requisite in tokamak.

Effect of ion beam current on dust charge fluctuations and ion-acoustic waves in electronegative dusty plasmas

The effects of ion beam current associated with the streaming positive ions on the dust charge fluctuations and ion acoustic wave propagation in quiescent electronegative dusty plasma have been investigated using fluid theory. The dust charging phenomenon and unstable mode of ion waves are modified for two streaming conditions of positive ions which are extended and graphically illustrated. The dependencies of the growing and damping rate of ion waves on dust density and the size of dust grains are studied. The evolution of dust surface potential is found in the negative domain with the increase in concentration of negative ions and the instability rate for ion wave decreases. Furthermore, it is shown that the dust surface potential shifts into positive domain as the electrons are significantly depleted (and the plasma becomes ion-ion plasma) from the electronegative plasma and thus ion waves exhibit a damping phenomenon.

Distribution of charge on floating dust particles over sunlit locations on Moon

Abstract The charging of fine particles within the photoelectron cloud is the key in characterizing the dusty plasma environment over sunlit locations. In this work, based on the statistical mechanics and charging kinetics of the floating dust particles within the photoelectron sheath over the sunlit lunar surface, the distribution of charge over floating particles has been investigated. The natural randomization of the dust charging currents, the anisotropy in sheath photoelectron population and electric field/ potential, and half Fermi Dirac velocity distribution of the emitted photoelectrons have been consistently accounted for in the formulation. In this framework, due to natural fluctuation, the charge on the floating dust particles is shown to be distributed over a wide range (∼100 e). This random fluctuation in charge might alter the static equilibrium of the floating dust particles and induce an altitudinal fluctuation (∼10%) about its mean position within the sheath. The concept and results suggest that the natural fluctuation of the dust charge could be a reason that the strict dust levitation under static force equilibrium is less likely to exhibit over the sunlit lunar surfaces. This effect of dust charge and subsequent altitudinal fluctuations have been found pronounced at larger latitudes (near the terminator region) and higher lunar altitudes.