Charged Dust Grains Research Articles

Parametric Excitation of Dust Acoustic Waves by Stimulated Scattering of an Electromagnetic Wave in Magnetized Dusty Plasmas

The nonlinear propagation of a high-amplitude electromagnetic (EM) wave is studied in a magnetized dusty plasma to investigate the three-decay instability in the stimulated scattering of the EM wave due to the density perturbations. The plasma involves the electrons, ions, and negatively charged dust grains, which are immersed in a uniform transverse magnetic field. Using the hydrodynamics plasma model and assuming the plasma ions to be stationary, a set of coupled equations is derived to find a new expression of the plasma frequency in magnetized dusty plasma as well as the instability growth rate of backward scattering. The effects of the external transverse magnetic field on the plasma frequency and the growth rate are reported.

Nonlinear propagation of dust-acoustic modes in a dusty plasma with the Kappa-Cairns polarization force effects

In this paper, the influence of Kappa-Cairns polarization force on solitary and periodic dust-acoustic (DA) waves is studied in a non-uniform dusty plasma containing negatively charged dust grains, Maxwellian electrons, and the Kappa-Cairns distributed ions. It is observed that in the presence of Kappa-Cairns distributed ions, the magnitude of the polarization force first increases as the spectral index increases and then decreases. The nonlinear Korteweg-de-Vries (K-dV) equation is obtained employing the reductive perturbation technique. The effects of polarization parameter (), Kappa-Cairns distribution parameters ( and ), and different ratios of ion to electron number densities () are investigated on the characteristics of DA solitary waves. We observed that the variations in the phase speed, amplitude, and width of DA solitons in the presence of the Kappa-Cairns polarization force are considerably different for case with respect to . The bifurcation theory of planar dynamical systems is also applied to investigate the existence of the solitary/periodic traveling wave in this plasma model. The phase portrait topology is illustrated for the K-dV equation. It is found that polarization force and other plasma parameters have a vital role in the traveling wave structures.

Influence of ions nonextensivity on the dynamics of dust acoustic double layers in a magnetized self-gravitating dusty plasma

The existence and polarity of dust acoustic double layers (DADLs) in a magnetized self-gravitating opposite polarity dusty plasma (OPDP) have been investigated. The constituents of the OPDP model are two species of positively and negatively charged dust grains, Maxwellian electrons, and nonextensive distributed ions. Employing the reduction perturbation method to solve basic fluid equations for dust grains, the extended Korteweg-de Vries (E-KdV) equation was derived, and its solution was extracted and analyzed. Results show that DADLs behavior is influenced by several new relevant configurational parameters, including the nonextensivity of ions, strength, and direction of the static magnetic field, as well as the self-gravitational field. In the proposed OPDP model positive and negative double-layer polarities may be formed. The polarity of OPDP is severely affected by the nonextensivity of plasma ions and the mass ratio of positive dusts to negatives. Results of higher-order nonlinear equation for solitary structure deny the presence of solitons in the physical condition of modeled plasma. In this work, simultaneous effects of an external magnetic field, self-gravitational force, and plasma ions’ nonextensivity have been studied extensively, which can be applied in various material processing plasmas, fusion plasmas, to space plasmas such as cometary tails, and Earth’s mesosphere.

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.

Numerical study of cosmic ray confinement through dust resonant drag instabilities

ABSTRACT We investigate the possibility of cosmic ray (CR) confinement by charged dust grains through resonant drag instabilities (RDIs). We perform magnetohydrodynamic particle-in-cell simulations of magnetized gas mixed with charged dust and cosmic rays, with the gyro-radii of dust and GeV CRs on ∼au scales fully resolved. As a first study, we focus on one type of RDI wherein charged grains drift super-Alfvénically, with Lorentz forces strongly dominating over drag forces. Dust grains are unstable to the RDIs and form concentrated columns and sheets, whose scale grows until saturating at the simulation box size. Initially perfectly streaming CRs are strongly scattered by RDI-excited Alfvén waves, with the growth rate of the CR perpendicular velocity components equaling the growth rate of magnetic field perturbations. These rates are well-predicted by analytic linear theory. CRs finally become isotropized and drift at least at ∼vA by unidirectional Alfvén waves excited by the RDIs, with a uniform distribution of the pitch angle cosine μ and a flat profile of the CR pitch angle diffusion coefficient Dμμ around μ = 0, without the ‘90○ pitch angle problem.’ With CR feedback on the gas included, Dμμ decreases by a factor of a few, indicating a lower CR scattering rate, because the backreaction on the RDI from the CR pressure adds extra wave damping, leading to lower quasi-steady-state scattering rates. Our study demonstrates that the dust-induced CR confinement can be very important under certain conditions, e.g. the dusty circumgalactic medium around quasars or superluminous galaxies.

On positively charged dust in the coma of comet 67P

ABSTRACT Moment analysis of ion spectrograms measured by the Ion Composition Analyser (ICA) in the coma of comet 67P typically produces an ion number density estimate markedly lower than the number density of free electrons as measured by the Mutual Impedance Probe and the dual Langmuir Probe. While there are good reasons to distrust the ion density moment estimate in these circumstances, the issue cannot yet be considered fully understood and it is of interest to see whether any natural non-instrumental cause is possible. An obvious such cause would be whether a significant fraction of the positive charge density resides in positively charged dust grains that are not measured by the ICA. Here, we show that this scenario is highly unlikely, even near perihelion where photoemission is the strongest. In our semi-analytical grain charging model, we balance the current contributions to grains of photoelectron emission and electron attachment so as to find the expected charge state for a grain of a given radius. The charge state is affected by the ambient electron number density, the electron temperature, and the heliocentric distance. While at times the bulk of the dust population around comet 67P could be charged positive, dust charging, including photoelectron emission, should have a negligible influence on the overall ionization balance in the cometary coma simply because the dust particles are not ubiquitous enough.

Electrostatic Shock Structures in a Magnetized Plasma Having Non-Thermal Particles

A rigorous theoretical investigation has been made on the nonlinear propagation of dust-ion-acoustic shock waves in a multi-component magnetized pair-ion plasma (PIP) having inertial warm positive and negative ions, inertialess non-thermal electrons and positrons, and static negatively charged massive dust grains. The Burgers’ equation is derived by employing the reductive perturbation method. The plasma model supports both positive and negative shock structures in the presence of static negatively charged massive dust grains. It is found that the steepness of both positive and negative shock profiles declines with the increase of ion kinematic viscosity without affecting the height, and the increment of negative (positive) ion mass in the PIP system declines (enhances) the amplitude of the shock profile. It is also observed that the increase in oblique angle raises the height of the positive shock profile, and the height of the positive shock wave increases with the number density of positron. The applications of the findings from the present investigation are briefly discussed.

Charging of dust grains weakly ionized plasma

The charging of dust grains in weakly ionized high pressure plasma is considered in drift-diffusion approximation which is valid for dusty plasma under high pressure as atmospheric plasma. The dependence of dust potential on the number density of grains and the temporal evolution grain charge are taken. It is shown that the charging time of grain in high pressure plasma is smaller than that of grain in low pressure plasma. By using the Poisons equation, the potential distribution around the dust particle is taken.

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.

On the Role of Electron Quantum Tunneling in Charging of Dust Grains in Complex Plasma

The role of the quantum tunneling effect in the electron accretion current onto a negatively charged grain immersed in isotropic plasma is analyzed, within the quasiclassic approximation, for different plasma electron distribution functions, plasma parameters, and grain sizes. It is shown that the contribution of the quantum tunneling into the grain charging is small (negligible) for relatively large (micron-sized) dust grains in plasmas with electron temperatures of the order of a few eV, but becomes important for nano-sized dust grains (tens to hundreds nm in diameter) in cold and ultracold plasmas (electron temperatures ~ tens to hundreds of Kelvin degrees), especially in plasmas with depleted high-energy "tails" in the electron energy distribution.

Influence of temporal variations in plasma conditions on the electric potential near self-organized dust chains

Self-organization of dust grains into stable filamentary dust structures (or “chains”) largely depends on dynamic interactions between individual charged dust grains and complex electric potential arising from the distribution of charges within a local plasma environment. Recent studies have shown that the positive column of the gas discharge plasma in the Plasmakristall-4 (PK-4) experiment at the International Space Station supports the presence of fast-moving ionization waves, which lead to variations of plasma parameters by up to an order of magnitude from the average background values. The highly variable environment resulting from ionization waves may have interesting implications for the dynamics and self-organization of dust particles, particularly concerning the formation and stability of dust chains. Here, we investigate the electric potential surrounding dust chains in the PK-4 experiment by employing a molecular dynamics model of the dust and ions with boundary conditions supplied by a particle-in-cell with Monte Carlo collision simulation of the ionization waves. The model is used to examine the effects of the plasma conditions within different regions of the ionization wave and compare the resulting dust structure to that obtained by employing the time-averaged plasma conditions. The comparison between simulated dust chains and experimental data from the PK-4 experiment shows that the time-averaged plasma conditions do not accurately reproduce observed results for dust behavior, indicating that more careful treatment of plasma conditions in the presence of ionization waves is required. It is further shown that commonly used analytic forms of the electric potential do not accurately describe the electric potential near charged dust grains under these plasma conditions.

Dust Acoustic Solitons in Saturn\u2019s Dust-Filled Magnetosphere

The possibility is considered of propagation of localized wave structures, such as dust acoustic solitons, in the plasma of the dust-filled Saturn’s magnetosphere, which contains electrons of two sorts (hot and cold) subject to kappa distribution, ions, and charged dust grains. The ranges of possible velocities and amplitudes of the solitons are determined. Soliton solutions for different sizes and concentrations of dust grains in the dust-filled Saturn’s magnetosphere are found.

Dust-acoustic solitary and periodic waves in magnetized self-gravito-electrostatic opposite polarity dusty plasmas

Dust-acoustic (DA) solitary and periodic waves investigations were performed in a magnetized self-gravitating dusty plasma consisting of negatively and positively charged dust grains in the presence of inertialess ions and electrons. The Korteweg–de Vries–Burger (KdVB) equation has been derived. The numerical investigations revealed the compressive or rarefactive DA solitons depending on the plasma parameters. The nonlinear homoclinic and periodic trajectories from the KdVB equation were obtained for the phase portrait profiles when employing the phase plane theory of dynamical systems. The periodic wave solution depends also on the system parameters. The present results are considered to be beneficial in understanding the nonlinear structures in experimental devices and different astrophysical environments such as the Earth’s mesosphere, cometary tails, and Jupiter’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.

Experimental study of charging of dust grains in the presence of energetic electrons

The role of hot electrons in the charging of dust grains is investigated in a two temperature hydrogen plasma. A variety of dust particles are introduced into the system and secondary electron emission (SEE) from each of the dust types has been reported. A cylindrical Langmuir probe is used for determining the plasma parameters and a Faraday cup is connected to an electrometer in order to measure the dust current. The electrometer readings confirm the electron emission from the dust and SEE is observed from the tungsten dust in a low-pressure experimental plasma device for the first time.

Dust-ion acoustic waves in magnetized plasmas with a varying external magnetic field

The problem of small amplitude dust-ion acoustic (DIA) solitary waves (SWs) is discussed using the reductive perturbation theory in a plasma containing thermal electrons, inertial ions, and negatively charged stationary dust grains under the influence of a varying magnetic field. Presented investigation shows that the effects of non-uniform magnetic fields and dust particles significantly modify the basic properties of the DIA solitary waves.

Dust ion acoustic solitons and double layers in a dusty plasma with adiabatic positive dust, adiabatic positive ion species, and Cairns-distributed electrons

The propagation of dust ion acoustic solitary waves and double layers is studied in a dusty plasma with heavy adiabatic positively charged dust grains and lighter adiabatic positive ions with Cairns-distributed electrons using the arbitrary amplitude Sagdeev pseudopotential approach. The analysis of the Sagdeev pseudopotential shows that this plasma model supports the propagation of positive solitons limited by the occurrence of the ion sonic point and negative solitons limited by the occurrence of double layers. Solitons of both polarities coexist for a range of some plasma parameters. We have shown that at a critical dust-to-ion density ratio, f, at which the third derivative of the Sagdeev pseudopotential vanishes, positive and negative solitons coexist without a soliton with finite amplitude at the acoustic speed, contrary to an earlier study. This suggests that the existence of a soliton with finite amplitude at the acoustic speed is not always a pre-requisite for the coexistence of nonlinear structures of both polarities. Positive and negative solitons coexist when the electrons are strongly nonthermal, with moderate ion thermal effects. Increasing ion thermal effect shifts the coexistence region to lower values of f, and when the ion thermal effects become important, negative solitons disappear and only positive solitons survive. The effects of different plasma parameters on the characteristics of the nonlinear structures have also been discussed in detail.

Redistribution of Kinetic Energy in Three-Dimensional Clouds of Charged Dust Grains

Redistribution of Kinetic Energy in Three-Dimensional Clouds of Charged Dust Grains

Dust–ion-acoustic waves in a [formula omitted]nonthermal magnetized collisional dusty plasma with opposite polarity dust

A four-component magnetized collisional κ−nonthermal plasma containing stationary dust grains of opposite charges, inertial ion fluid, and non-inertial κ−distributed superthermal electrons has been considered to study different modes of dust–ion-acoustic waves (DIAWs) theoretically and numerically. The ion-neutral collisional effect and the adiabatic effect of warm ions have been taken into account to study the properties of DIAWs in the considered plasma. A reductive perturbation method is adopted to derive the damped Zakharov–Kuznetsov–Burgers (dZKB) equation and the solution (solitary and shock) of the dZKB equation is used to examine the basic features (e.g., speed, amplitude, energy, width, etc.) of dust–ion-acoustic solitary and shock waves. The influence on the dust–ion-acoustic soliton and shock characteristics of relevant physical plasma parameters such as adiabaticity, superthermality, viscosity, obliqueness, magnetic field, the amount of charge residing onto the dust grains, collision effect is examined. Additionally, the impact of the coexistence of oppositely charged dust grains on the dynamical properties of dust–ion-acoustic soliton and shock waves is analyzed. The findings of this research work may be applied to examine the properties of DIAWs in experimental and space dusty plasmas, where the opposite polarity dust grains are present, adiabatic thermal pressure of warm ion and damping due to ion-neutral collision are accountable.

Radiative transfer of ionizing radiation through gas and dust: grain charging in star-forming regions

ABSTRACT The presence of charged dust grains is known to have a profound impact on the physical evolution of the multiphase interstellar medium (ISM). Despite its importance, this process is still poorly explored in numerical simulations due to its complex physics and the tight dependence on the environment. Here, we introduce a novel implementation of grain charging in the cosmological radiative transfer code crash. We first benchmark the code predictions on a series of idealized dusty H ii regions created by a single star, in order to assess the impact of grain properties on the resulting spatial distribution of charges. Secondly, we perform a realistic radiative transfer simulation of a star-forming region extracted from a dusty galaxy evolving in the Epoch of Reionization. We find that ∼13 per cent of the total dust mass gets negatively charged, mainly silicate and graphite grains of radius 10−3 $\mu$m. A complex spatial distribution of grain charges is also found, primarily depending on the exposure to stellar radiation and strongly varying along different lines of sight, as a result of radiative transfer effects. We finally assess the impact of grain properties (both chemical composition and size) on the resulting charge distribution. The new implementation described here will open up a wide range of possible studies investigating the physical evolution of the dusty ISM, nowadays accessible to observations of high- and low- redshift galaxies.