Grains In Dusty Plasma Research Articles

Dust dynamics in the lunar dusty plasmas: Effects of magnetic fields and dust charge variations

The influence of the magnetic field of the Earth's magnetotail on dusty plasmas above the sunlit surface of the Moon is studied. For this purpose, a physical-mathematical model for a self-consistent description of dust grains and photoelectrons in the presence of the magnetic field is developed. Trajectories of motion of dust grains above the lunar surface are considered. It is shown that a distinguishing feature of the trajectory of a dust grain motion is the presence of oscillations. The process of damping of these oscillations is demonstrated to be related to variations of dust grain charges that is consistent with the concept of anomalous dissipation in dusty plasmas. We clarify whether dust grains in dusty plasmas above the sunlit lunar surface are “levitated” or “lofted.” The processes of dust grain charge variations are too fast in comparison with the day duration of the Moon. In this connection, for the majority of dust grains above the sunlit lunar surface, the oscillations are damped, and these grains can be considered as levitated. Only very fine grains do not go into “levitating” grain mode during the entire day on the Moon and can be treated as lofted those. A theory of dusty plasmas above the sunlit surface of the Moon, which takes into account the lunar gravity and the electrostatic processes but does not take into account the magnetic fields, explains the existence of dusty plasmas only for rather high lunar latitudes. The magnetic fields of the Earth's magnetotail are shown to provide a possibility of dust transport above the lunar surface, which can result in the existence of positively charged dust and correspondingly dusty plasmas at the sunlit side of the Moon for the whole range of the lunar latitudes.

Highly Efficient Heavy Ion Acceleration from Laser Interaction with Dusty Plasma

Energetic heavy ions with short duration can be generated in the interaction of ultrashort ultraintense (USUI) laser pulse with solid matter. However, the energy conversion efficiency from laser to heavy ions is usually very low. Herein, a novel scheme for efficient transfer of USUI laser energy to the heavy ions of microscopic dust grains in dusty plasma is proposed. Due to the resulting ultraintense space‐charge field, the heavy ions expand isotropically together with the laser heated and expelled grain electrons as a plasma cloud on roughly the ion acoustic timescale. It is found that with 3.1 × 1020 W cm−2 USUI laser, one can produce hundreds‐megaelectronvolt C6+ ions with ≈60% energy transfer efficiency. In fact, up to 300 GeV Au79+ ions with ≈30% energy transfer efficiency can be obtained by using 8.8 × 1023 W cm−2 laser. This result suggests the possibility of using hundreds‐petawatt laser facility to investigate heavy‐ion collisions for nuclear state detection and quantum cardiodynamics phase transition.

Generalized non-ideal treatment and growth rates analysis of drift waves instabilities in a collisions-free magnetized dusty plasma

Dust acoustic wave propagation in weak magnetized homogeneous dusty plasmas has been extensively and successfully studied by different authors. Here, it is analyzed the behavior of electrostatic drift waves of very low frequency, appearing as due to the motion of plasma particles across the static magnetic field and the inhomogeneity introduced by the distribution of the particles in the dusty plasma generating the well-known diamagnetic effect. To study this situation, the kinetic Vlasov model in plasmas will be used. However, these models tend to behave unstably driven by the quasi-equilibrium of the diamagnetic current arising by the heavier species of dusty plasma particles. While other authors have used a standard state equation, such as the Van der Waals one, here, a more accurate model has been chosen as the equation of Ree and Hoover, a state equation that can be considered as a new form of the state equation. Together with the multipole approximation of the dispersion function, Z53 [P. Martin et al., J. Math. Phys. 21, 280–283 (1980)] allows a new derivation to obtain the simplest form of the dispersion relation in the form of a polynomial with complex coefficients. This mathematical approach was realized successfully and allowed straightforward calculus of the growth rate due to the drift unstable mode. This problem has been extensively analyzed in this work, including the non-ideal effect of dusty plasmas. These unstable modes are well discriminated and plotted as a function of the density of the grains in dusty plasma and their radius. Temperature gradients and charge fluctuation have been ignored.

Analiz potentsial'noyi enerhiyi systemy vzayemodiyuchykh chastynok, uporyadkovanykh u gratku Brave

We propose a method to calculate the type of a lattice formed by grains in dusty plasma and estimate its potential energy. Basically, this task is complicated by the interparticle potential that appertains to “catastrophic potentials”. This kind of potentials needs special approaches to avoid divergences during potential energy calculations. In the current contribution, we will develop all the necessary modifications to appropriate methods. It will be shown that the obtained potential energy expression can be used to determine lattice parameters and these parameters comply to known experimental data.

Complex motions of grains in dusty plasma with nonuniform magnetic field

We have studied various complex motions of the irregular dust grains immersed in non-uniformly magnetized plasma. The cylindrical magnet that we used for experiments significantly alters the radial distribution of the sheath potential which confines the negatively charged grains. Grains are horizontally illuminated by a 50 mW, 532 nm laser sheet and imaged by a CCD camera from the upper transparent electrode. Hypocycloid and epicycloid motions of grains are observed for the first time as far as we know. Cuspate cycloid motions, circle motion, wave motion, and stationary grains are also observed. Their trajectories can be obtained by using long-time exposure, and the characteristic parameters of the grain movement are measured by using the image processing with MATLAB. Though the dust grains can move around the magnet steadily in various trajectories, the induced magnetic field is too weak to give rise to cycloid motions of grains. Then we propose a new mechanism that an inverse Magnus force induced by the spin of the irregular grains plays an important role in their cycloid motions. The pollen pini we used for experiment is not a regular microsphere, there is a symmetry in the shape. On the basis of Bernoulli principle, the pressure difference between the left and right side of the forward moving grains produces the inverse Magnus effect. Additional comparison experiments with regular microspheres are also performed to confirm that the cycloid motions are distinctive features of an irregular dust grain immersed in the plasma. The periodical change of the cyclotron radius as the grain travels would result in the (cuspate) cycloid motions, and the maximal value of angular velocity of spin is about 105 rad/s. Our experimental observations can be well explained based on the force analysis in 2D horizontal plane.

Vortices of self-gravitating grains in dusty plasmas

Vortices are an attractive expression of the non-linear dynamics of fluids along with plasmas. In complex plasmas, Nebbat and Annou [Phys. Plasmas 17, 093702 (2010)] proposed a time dependent non-linear model that considers vortices as a consequence of an instability. The model is augmented hereafter by incorporating the gravitational grain-grain attraction, particle drift due to self-gravity field, self-consistent inter-particle distance, the permeability of grains along with the grain charge excess due to the non-linear dependence of the grain capacitance on its size. Effects of the latter parameters as well as the effect of grain mass to charge ratio on the characteristics of the vortex such as density are investigated.

Plasma absorption effects on collisions of positively charged dust grains in dusty plasmas

The plasma absorption effects on the collisions of positively charged dust grains are investigated in dusty plasmas. The method of stationary phase and the effective interaction potential containing the attractive part are employed to obtain the scattering cross-section between a pair of positively charged dust grains as a function of the impact parameter, collision energy, electron and ion temperatures, and Debye length. The result shows that the plasma absorption effects on the dust surface strongly suppress the total scattering cross-section. It is also shown that the plasma absorption effects on the scattering cross-section decrease with an increase of the ratio of the electron temperature to the ion temperature. In addition, the plasma absorption effects are found to be decreased with increasing the collision velocity.

Ponderomotive transport of charged grains in dusty plasma

The ponderomotive force with which a rapidly oscillating electric field of dusty plasma acts on a charged grain in this plasma is considered. Allowance for the field-induced charge oscillations in the grain reveals new components of the ponderomotive force, which have not been previously described in the literature. One of these components is nonvanishing even in the case of homogeneous plasma and field, which results in a directed transport of the charged fraction of dusty plasma.

Structure formation in system of Brownian particle in dusty plasma

The stationary distribution function of grains in a dusty plasma is calculated with regard to electron and ion absorption by grains. It is shown that such distribution can be considerably different from the distribution function of ordinary Brownian particles in thermal equilibrium. The criterion of formation of non-equilibrium spatially ordered distributions of grains in dusty plasmas is discussed.

Klimontovich's contributions to the kinetic theory of nonlinear Brownian motion and new developments

We review the concept of nonlinear Brownian motion, originally introduced by Klimontovich, and consider several applications to real systems, including e.g. atoms, molecules or ions laser cooling fields, charged grains in plasmas and interdisciplinary problems. In particular, we also discuss recent developments in the field of active Brownian particles. After summarizing the basic properties of active Brownian particle models, solutions of the corresponding Fokker-Planck equation are analyzed for free motions as well as for motions in confining fields. Furthermore, we study the distributions for finite systems of self-confined particles, interacting via Morse and Coulomb potentials. Finally, applications to clusters of atoms subject to laser cooling as well as to clusters of charged grains in dusty plasmas are discussed.

Spinning of Spherical Grains in Dusty Plasmas

It is shown that the angular momentum transfer to spherical dust grain from ion flux in the process of grain charging is not zero if the ion attachment coefficient at the grain surface is inhomogeneous. An exact analytical solution is found for a spherical grain having the ion attachment coefficient in one hemisphere /spl kappa//sub +/ different from that in the other hemisphere /spl kappa//sub $/and for the charge being uniformly distributed on the grain sphere. The transfer of the angular momentum occurs in presence of the ion flow determined by the ion drift velocity u. The direction of the angular momentum and the direction of the grain rotation axis is determined by the vector product [u /spl times/ n], where n is a unit vector directed from one hemisphere with /spl kappa//sub +/ to another hemisphere with /spl kappa//sub -/. The angle /spl theta/ between n and u determines the range of impact parameters and the range of impact angles of ions which reaches either one or the other grain hemisphere. This gives an analytical algebraic equation for the range of angles of the impact parameters of ions in the plane perpendicular to the flow which determines the transfer of the angular momentum. The solution of this equation and integration with respect to the impact parameters is obtained numerically. The angular momentum transfer is proportional to (/spl kappa//sub +/-/spl kappa//sub -/)2u/sup 2/a/sup 2/m/sub i/sin(/spl theta/)F(/spl theta/,z), where z=2Z/sub d/e/sup 2//am/sub i/u/sup 2/ is the dust dimensionless charge, a is the dust radius, and m/sub i/ the ion mass. The function F(/spl theta/,z) is found numerically and for z=2 is approximately equal to F=1+0.24sin/sup 8/(/spl theta/). With the decrease of z, the absolute value of F (reached at sin(/spl theta/)=1) gradually decreases and for z=0.1 it is equal to 0.001. The terms with larger power of sin/sup 2/(/spl theta/) are prevailing at smaller values of the dust charges. The solution of the equation for the dust rotation was found by taking into account the angular momentum transfer in charging, the friction in neutral gas, and the dust angular momentum inertia. It is shown that in general, after switching on the ion flow, the dust rotates several times until it is aligned to the ion flow (vectors n and u being antiparallel). The number of rotations depends on the the ratio of the friction force to the angular momentum inertia force. The effect of the grain alignment to the ion flow can be used both for the nonmagnetic and ferromagnetic dust grains. The ferromagnetic dust grains can be used to create magnetic fields by dust in absence of external magnetic fields. Continuous dust rotation can be excited by a modulated ion flow.

String effects on elastic collisions of ions with strings of dust grains in dusty plasmas

The elastic collision of ions with strings of strongly coupled dust grains in dusty plasmas is investigated using the eikonal analysis. The dust string has been considered as the one-dimensional model for strongly coupled dusty plasmas. The impact parameter method is applied to investigate the variation of the eikonal phase and elastic cross section as functions of the Debye length, number of dust grains, spacing of dust grains, and collision energy. The result shows that the eikonal phase and the total scattering cross section are increased with increasing Debye length. It is also found that the eikonal phase increases with increasing dust spacing, i.e., the length of dust string, and with the increasing number of dust grains due to the collective effects.

THERMODYNAMIC REASONS OF AGGLOMERATION OF DUST PARTICLES IN THE THERMAL DUSTY PLASMA

The thermodynamic equilibrium of thermal dusty plasmas consisting of ionized gas (plasma) and solid particles (dust grains), which interact with each other, is studied. The tendency of grains in dusty plasmas to agglomerate corresponds to the tendency of dusty plasmas to balanced states. When grains agglomerate, electrical perturbations generated by each grain concentrate inside the agglomerate. The plasma is perturbed only by the agglomerate’s exterior surface. The greater number of possible states for electrons and ions in plasma depends on the volume of perturbation of grains. The fewer are the perturbations the greater is the amount of possible states for electrons and ions in plasma. If the grains collected from a distance smaller than 8 Debye lengths, the total volume of perturbations is minimized; the free energy of the plasma is also minimized.

Dressing effects on elastic collisions in dusty plasmas.

Elastic collisions between two dressed grains charged with the same sign in dusty plasmas are investigated using the first- and second-order eikonal method. An interaction potential model taking into account the cross terms of shield effects is applied to describe the interaction potential between dressed dust grains in dusty plasmas. The impact parameter method is applied to investigate the variation of the eikonal phase and elastic cross section as functions of dust charge, Debye length, and collision energy. The result shows that the potential well in the interaction potential plays an important role in the elastic cross section as well as in the eikonal phase. It is also found that the dressing effects significantly increase the elastic cross section and change the sign of the eikonal phase. It is also found that the second-order eikonal phase is caused by the pure plasma screening effects.

Debye shielding distortion of dust grains in dusty plasmas

The shielded potential and the energy loss of N2 projectiles propagating through a multicomponent dusty plasma are studied. Analytically general expressions have been obtained for the potential and for the energy loss, taking into account the two-body correlation effects. However, numerical calculations have been performed for one, three, and six projectiles, incorporating interference between two consecutive projectiles. It is found that the correlation effect causes distortion in the potential profile depending upon the separation between the two projectiles. The distortion becomes pronounced for separation smaller than the Debye length.

Bremsstrahlung emission from interactions between two dressed dust grains in dusty plasmas

Bremsstrahlung emission from interactions between two dressed grains charged with the same sign in dusty plasmas are investigated using the classical trajectory method. An interaction potential model taking into account the cross terms of shield effects is applied to describe the interaction potential between dressed dust grains in dusty plasmas. The classical straight-line trajectory method is applied to represent the bremsstrahlung cross section as a function of the scaled impact parameter, collision energy, and photon energy. The result shows that the potential well in the interaction potential plays an important role in the bremsstrahlung spectrum. It is also found that there exists a nonradiation position in the bremsstrahlung radiation due to the balance between the repulsive and attractive interactions.

Image charge effects on electron capture by dust grains in dusty plasmas.

Electron-capture processes by negatively charged dust grains from hydrogenic ions in dusty plasmas are investigated in accordance with the classical Bohr-Lindhard model. The attractive interaction between the electron in a hydrogenic ion and its own image charge inside the dust grain is included to obtain the total interaction energy between the electron and the dust grain. The electron-capture radius is determined by the total interaction energy and the kinetic energy of the released electron in the frame of the projectile dust grain. The classical straight-line trajectory approximation is applied to the motion of the ion in order to visualize the electron-capture cross section as a function of the impact parameter, kinetic energy of the projectile ion, and dust charge. It is found that the image charge inside the dust grain plays a significant role in the electron-capture process near the surface of the dust grain. The electron-capture cross section is found to be quite sensitive to the collision energy and dust charge.

Stationary velocity and charge distributions of grains in dusty plasmas

Within the kinetic approach the velocity and the charge distributions of grains in stationary dusty plasmas are calculated and the relations between the effective temperatures of such distributions and plasma parameters are established. It is found that the effective temperature which determines the velocity grain distribution could be anomalously large due to the action of accelerating ionic bombarding force. The possibility to apply the results obtained to the explanation of the increasing grain temperature in the course of Coulomb-crystal melting by reduction of the gas pressure is discussed.

Interaction of Grains in Dusty Plasmas

Plasma absorption by dust grains results in anisotropy of plasma distribution function. This yields the effective attractive interaction between grains. Here a brief review of physical properties of this interaction is given. First we demonstrate that there is the attracting force between two grains obeying the inverse square low. Then a set of kinetic equations taking into account both attracting and repulsing forces is proposed. We study a simple model of dust cloud consisting of finite number of grains. It is shown that even within gaseous approximation a dust cloud is a compact object with a sharp boundary. Finally, we discuss recent experiments aimed to detecting the attractive force between massive bodies.