Long-time evolution of charged grains in plasma under harmonic external force and after being withdrawn

Evolution of the charged grains in a two-dimensional dusty plasma under a spatially harmonic external force,in particular,their long-time behaviors after the force has been withdrawn,is studied by using molecular dynamics simulation.Under an external force and a grain–grain interaction force,initially homogeneously distributed grains can reach a quasistationary state in the form of a disk crystal.After the external force is withdrawn,the disk moves initially with its size and shape nearly unchanged until it rapidly stops moving,and eventually the disk grain rotates like a vortex.The time needed to reach the final state increases with the strength of the initial external force increasing.     

Effects of polarization force and nonthermal ions on dust-acoustic (DA) shock waves in a strongly coupled dusty plasma with positively charged dust

The nonlinear propagation of the dust-acoustic (DA) waves in a strongly coupled dusty plasma containing Maxwellian electrons, nonthermal ions, and positively charged dust is theoritically investigated by a Burgers equation. The effects of the polarization force (which arises due to the interaction between electrons and highly positively charged dust grains) and nonthermal ions are studied. DA shock waves are found to exist with positive potential only. It represents that the strong correlation among the charged dust grains is a source of dissipation, and is responsible for the formation of DA shock waves. The effects of polarization force and nonthermal ions significantly modified the basic features of DA shock waves in strongly coupled dusty plasma.     

Self-Organization of Charged Particulates in the Presence of External Force

Evolution of spatial distribution of charged particulates under the action of an external force is investigated.It is found that starting from a homogeneous Maxwellian distribution of particulates,clusters can form and aggregate.The evolution process,as well as the asymptotic number and configuration of the clusters formed,depends strongly on the strength of the external force.The particulates in most of the final clusters are in the crystal state,as can also be deduced from the corresponding velocity and auto-correlation functions.     

Acceleration of dust grains by means of the high energy ion beam

The acceleration of charged dust grains by a high energy ion beam is investigated by obtaining the dispersion relation. The Cherenkov and cyclotron acceleration mechanisms of dust grains are compared with each other. The role of dusty plasma parameters and the magnetic field strength in the acceleration process are discussed. In addition, the stimulated waves by an ion beam in a fully magnetized dust–ion plasma are studied. It is shown that these waves are unstable at different angles with respect to the external magnetic field. It is also indicated that the growth rates increase by either increasing the ion and dust densities or decreasing the magnetic field strength. Finally, the results of our research show that the high energy ion beam can accelerate charged dust grains.     

Effect of polarization force on the Jeans instability of self-gravitating dusty plasma

The effect of polarization force acting on massive charged dust grains is investigated analytically on the Jeans instability of self-gravitating dusty plasma. The gravitational force acting on the massive negatively charged interstellar dust grains are considered in presence of both electrical and polarization forces. The basic equations of the problem are formulated and a general dispersion relation is obtained using plane wave approximation in low frequency wave mode. The effect of polarization force in the dispersion relation of the problem, condition of the Jeans instability and expression of the critical Jeans wave number is examined. The unstable growing modes due to self-gravitational force are studied in the situation when polarization force on the dust grain exceeds over the electrical force in magnitude. It is observed that the polarization force increases the growth rate of the system.     

Three-dimensional wake potential in a streaming dusty plasma

The oscillatory wake potential for a slowly moving or static test dust particulate in a finite temperature, collisionless and unmagnetized dusty plasma with a continuous flow of ions and dust particles has been studied. The collective resonant interaction of the moving test particle with the low-frequency and low-phase-velocity dust-acoustic mode is the origin of the periodic attractive force between the like polarity particulates along and perpendicular to the streaming ions and dust grains resulting into dust-Coulomb crystal formation. This wake potential can explain the three-dimensional dust-Coulomb crystal formation in the laboratory conditions.     

Effects of dust-charge gradient and polarization forces on the waves and Jeans instability in strongly coupled dusty plasma

The effects of dust charge gradient (DCG) force and polarization force have been investigated on the properties of dust acoustic wave (DAW) and linear Jeans instability in strongly coupled dusty plasma. In the kinetic regime, DCG and polarization forces modify the DAW mode and couple with compressional viscoelastic wave mode. The Jeans instability criterion and critical wavenumber have been modified due to DCG force, polarization force and strong coupling effects. The results have been discussed in the warm photodisassociation region and in the laboratory complex plasmas. The strong correlation effect and the charge variation parameter stabilize the growth rate of Jeans instability. But, the polarization parameter stabilize the growth rate for positively charged dust grains and destabilize for negatively charged dust grains. The implications of charge gradient and polarization parameters are discussed for lower and higher charges in the laboratory complex plasma which decreases the growth of the propagating DAW.     

Effect of levitated dust kinetics in the dynamic evolution of inhomogeneous plasma sheath

The main goal here is to study theoretically the formation of plasma sheath in an inhomogeneous dusty plasma. The effect of weak ionization of the dust grains as similar to the Townsend discharge has been incorporated to see how it influences the evolution of sheath. Sheath equation has been derived to describe the properties of sheath structures analytically and numerically. It has shown that the ionization along with the inhomogeneity affects significantly the growth of sheath which has been highlighted elaborately for some typical plasma parameters. After getting well defined sheath region, dynamical behaviour of levitated dust grains into the sheath has been studied. The totality of the findings has been centred around the estimation of dust surface potential, dust sizes along with the generation of net force on dust grains. Both inhomogeneous and ionization effects allow the dust grains in acquiring different potential to sustain equilibrium in different places. As a result of this, nebulons and the dust cloudlike structures are electrically charged.     

Ordered dust structures in glow discharge plasmas

Ordering of dust grains suspended in glow discharge plasmas into quasi-steady liquid-or crystallike structures in an external field is considered. The self-consistent electric field generated by free electrons, ions, and dust grains is found. An estimate is obtained for the confining potential required to hold dust grains in the direction perpendicular to the discharge axis. It is shown that the potential energy of interaction between ordered dust particles has the form characteristic of ionic crystals. Critical parameters are estimated for a liquidlike dust structure. The correlation function calculated for a dusty plasma by using this approach is compared with a measured one.     

Electrodynamics and dispersion properties of a magnetoplasma containing elongated and rotating dust grains

The electrodynamics and dispersion properties of a magnetized dusty plasma containing elongated and rotating charged dust grains are examined. Starting from an appropriate Lagrangian for dust grains, a kinetic equation for the dust grain and the corresponding equations of motion are derived. Expressions for the dust charge and dust current densities are obtained with the finite size (the dipole moment) of elongated and rotating dust grains taken into account. These charge and current densities are combined with the Maxwell-Vlasov system of equations to derive dispersion relations for the electromagnetic and electrostatic waves in a dusty magnetoplasma. The dispersion relations are analyzed to demonstrate that the dust grain rotation introduces new classes of instabilities involving various low-frequency waves in a dusty magnetoplasma. Examples of various unstable low-frequency waves include the electron whistler, the dust whistler, dust cyclotron waves, AlfvÉn waves, electromagnetic ion-cyclotron waves, as well as lower-hybrid, electrostatic ion cyclotron, modified dust ion-acoustic waves, etc. Also found is a new type of unstable waves whose frequency is close to the dust grain rotation frequency. The present results should be useful in understanding the properties of low-frequency waves in cosmic and laboratory plasmas that are embedded in an external magnetic field and contain elongated and rotating charged dust grains.     

Electrostatic sheath at the boundary of a collisional dusty plasma

Considering the Boltzmann response of the ions and electrons in plasma dynamics and inertial dynamics of the dust charged grains in a highly collisional dusty plasma, the nature of the electrostatic potential near a boundary is investigated. Based on the fluid approximation, the formation as well as the characteristic behaviours of the sheath is studied. It is expected that the presence of dust charged grains will lead to a very different behaviour of the sheath as compared to that of electron-ion plasma. Moreover, the collisions of the dust charged grains with the neutrals are expected to exhibit novel features.     

Streaming instability in quantum dusty plasmas

By using a quantum hydrodynamic (QHD) model, we derive a generalized dielectric constant for an unmagnetized quantum dusty plasma composed of electrons, ions, and charged dust particulates. Neglecting the electron inertial force in comparison with the electron pressure, and the force associated with the electron correlations at a quantum scale, we discuss two classes of electrostatic instabilities that are produced by streaming ions, and dust grains. The effects of the plasma streaming speeds, the thermal speed of electrons, and the quantum parameter are examined on the growth rates. The relevance of our investigation to dense astrophysical plasmas is discussed.     

The dust acoustic wave in a bounded dusty plasma with strong electrostatic interactions between dust grains

The dispersion relation for the dust acoustic wave (DAW) in an unmagnetized dusty plasma cylindrical waveguide is derived, accounting for strong electrostatic interactions between charged dust grains. It is found that the boundary effect limits the radial extent of the DAW. The present result should be helpful for understanding the frequency spectrum of the DAW in a dusty plasma waveguide with strongly coupled charged dust grains.     

Forces on a small grain in the nonlinear plasma wake of another

The transverse force on a spherical charged grain lying in the plasma wake of another grain is analyzed to assess the importance of ion-drag perturbation, in addition to the wake-potential-gradient. The ion-drag perturbation is intrinsically one order smaller than the wake-potential force in the ratio of grain size (r(p)) to Debye length (λ(De)). So ion-drag perturbation is important only in nonlinear wakes. Rigorous particle-in-cell calculations of the force are performed in the nonlinear regime with two interacting grains. It is found that even for quite large grains, r(p)/λ(De)=0.1, the force is dominated by the wake-potential gradient. The wake-potential structure can then help explain the preferred alignment of floating dust grains.     

Effect of the Polarization Force on the Dust–Acoustic Soliton Energy

The role the polarization force acting on dust particles may play on the energy carried by the dust‐acoustic (DA) soliton is examined. This force is due to the deformation of the Debye sheath around the dust particulates in the background of non‐uniform plasmas. The energy carried by the DA solitons is derived. This energy decreases with an increase in the effects of plasma‐dust particles polarization interaction. This means that when the magnitude of the polarization force approaches the one of the electrical force, i.e, the net force acting on the grains decreases, the DA soliton energy experiences a depletion. As noticed by Khrapak et al. [S.A. Khrapak et al., Phys. Rev. Lett. 102 , 245004 (2009)], when the polarization force dominates over the electrical one, the plasma can not support DA solitons. This happens whenever the dust grain size exceeds a critical threshold. In this case, the net force acting on the grains is no longer a restoring force. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Interaction of a dielectric macroparticle with a point charge in plasma

The electrostatic interaction of a charged spherical dielectric macroparticle with a point charge in a plasma in the presence of an external uniform electric field is considered. The electrostatic force and the torque acting on the macroparticle have been determined, and the form of the interaction potential has been established for a nonuniform distribution of free charge on the macroparticle surface. A simple (for calculations) expression for the interaction potential that describes well the exact potential at all interparticle distances is proposed. The angular velocity of the spinning of dust particles caused by a nonuniform distribution of free charge over their surface has been estimated.     

Large-amplitude dust acoustic solitons in an opposite polarity dusty plasma with generalized polarization force

Linear and nonlinear dust acoustic(DA)waves have been investigated in an opposite polarity dusty plasma comprising negatively and positively charged dust grains,Maxwellian electrons and ions,including the generalized polarization force effect.The properties of linear DA waves have been significantly altered by the dual dust polarity and polarization force.Large amplitude DA solitons have been discussed in the framework of the Sagdeev potential technique.Our results show that both rarefactive and compressive solitons can exist in such a dusty plasma.The basic features of the Sagdeev potential have been examined under the effect of the polarization force parameter R,the ratio of the charge number of the positive dust to that of the negative dust Z,and the Mach number M.The results show that these parameters play a significant role in determining the region of existence of large amplitude DA solitons.     

On the role of dust in the cometary plasma

The cometary coma consists of neutral gas, plasma, and dust grains. The dust grains can influence both the neutral and charged coma’s constituents. Usually, the presence of dust particles in a plasma results in additional losses of both electrons and ions due to the plasma recombination on the particle surfaces. Solar radiation makes the impact of dust even more complicated depending on the solar flux, the dust number density, the photoelectric properties of the dust particles, the dust particle composition, the distribution of the sizes, etc. We propose a simple kinetic model evaluating the role of dust particles in the coma plasma chemistry and demonstrate that this role can be crucial, resulting in a nontrivial behavior of both the electron and ion densities of the plasma. We show that a coma’s dust particles can be negatively as well as positively charged depending on their composition. These opposite charges of the grains can result in fast coagulation of dust particles, thus, forming complex aggregate shapes of cometary grains. The text was submitted by the authors in English.     

Resonant interaction of the Langmuir wave with quasi-stationary plasma electrons

Evolution of the Langmuir wave in quasi-stationary plasma is considered. A consistent solution to the closed system of the Vlasov–Poisson equations is obtained in the adiabatic approximation. Dispersion of the wave evolving in the electron distribution tail with variable electron concentration or plasma temperature is described. It is established that the plasma oscillation energy increases with decreasing electron concentration or increasing temperature. After plasma regains its initial state, the wave parameters also restore their initial values. That is, the wave evolution in the quasi-stationary plasma is a completely reversible process.