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The effect of dust grain pressure on the head‐on collision of two dust‐acoustic solitary waves in non‐magnetized, collisionless, and strongly coupled dust plasma has been investigated [J. Plasma Phys. (2020), 86, 905,860,111]. In this paper, the model is augmented by incorporating the ion drag force on dust grains. By way of the extended perturbation method of Poincaré‐Lighthill‐Kuo, Korteweg‐de Vries equations are derived. The wave characteristics along with the phase shifts after the head‐on collision are analytically established and numerically assessed. It revealed a non‐negligible decrease in the wave amplitude and the phase shift. [ABSTRACT FROM AUTHOR]

In this paper, the problem of large amplitude dust acoustic (DA) solitons has been addressed in a charge varying dusty plasma with ions following a Cairns‐Gurevich distribution. Based on the orbit motion limited approach, the correct Cairns‐Gurevich ion charging current is presented for the first time. The expression relating the variable dust charge to the plasma potential is given in terms of the Lambert function and we take advantage of this transcendental function to, carefully, analyse DA solitons in a charge varying dusty plasma with trapped nonthermal ions. Our results show that the spatial patterns of the variable charge solitary wave are significantly changed due to the presence of ion population modelled by the Cairns‐Gurevich distribution. An addition of a small concentration of trapped nonthermal ions makes the solitary structure less spiky, grows the net negative charge residing on the dust grain surface, and contributes to the electron depletion. Finally, our investigation is extended to highlight the effect of the grain dust charge variation. We have shown that under certain conditions, the impact of dust charge fluctuation may furnish an alternate physical mechanism rasing anomalous dissipation, which becomes more strong and may predominate over the dispersion as the nonthermal character of ions following the Cairns‐Gurevich distribution increases. [ABSTRACT FROM AUTHOR]

This paper reports experiments on self‐excited dust acoustic waves (DAWs) and its propagation characteristics in a magnetized rf discharge plasma. The DAWs are spontaneously excited in dusty plasma after adding more particles in the confining potential well and found to propagate in the direction of streaming ions. The spontaneous excitation of such low‐frequency modes is possible due to the instabilities associated with streaming ions through the dust grain medium. The background E‐field and neutral pressure determine the stability of excited DAWs. The characteristics of DAWs strongly depend on the strength of external magnetic field. The magnetic field of strength B < 0.05 T only modifies the characteristics of propagating waves in dusty plasma at moderate power and pressure, P = 3.5 W and p = 27 Pa, respectively. It is found that DAWs start to be damped with increasing the magnetic field beyond B > 0.05 T and get completely damped at higher magnetic field B ∼ 0.13 T. After lowering the power and pressure to 3 W and 23 Pa respectively, the excited DAWs in the absence of B are slightly unstable. In this case, the magnetic field only stabilizes and modifies the propagation characteristics of DAWs while the strength of B is increased up to 0.1 T or even higher. The modification of the sheath electric field where particles are confined in the presence of the external magnetic field is the main cause of the modification and damping of the DAWs in a magnetized rf discharge plasma. [ABSTRACT FROM AUTHOR]

PIV images of a dusty plasma (obtained after averaging 50 images) flow in a horizontal plane at different vertical locations of confined dust grains in a potential well. (a) Topmost dust grains (b) 2mm below the topmost dust grains plane, (c) 4mm lower than the topmost dust grains plane, (d) 6mm lower than the topmost dust grains plane. Fig. 5 of the paper by Mangilal Choudhary. https://doi.org/10.1002/ctpp.202300072. [Extracted from the article]

Although most experiments in complex plasmas correspond to non-linear grain screening, the theoretical models of non-linear screening have not been checked experimentally. Scattering of electromagnetic waves on a single nonlinearly screened dust grain in plasmas can serve as one of effective methods for investigation of non-linear screening. In present paper we have developed a theory for electromagnetic wave scattering that includes both the effect of coherency of scattering for long wave range and the loss of coherency with a decrease of the wave length. It is valid for arbitrary non-linearity in screening and demonstrates that the loss of coherency occurs for wave length less then the characteristic screening length for non-linear screening being usually substantially larger than the linear Debye screening length. The effect is illustrated numerically using the most popular model of non-linear screening. The dependence of the cross-section of scattering on parameter of non-linearity in screening is calculated numerically. The loss of coherency in scattering by a single grain can serve as effective diagnostic for checking the theoretical models of non-linear screening. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

This special issue of CPP is devoted to the memory of an outstanding Russian physicist - Academician Vladimir Fortov (January 23, 1946-November 29, 2020). He made outstanding contributions to the physics of extreme states of matter and to the physics of high energy densities, the physics of shock and detonation waves, thermal physics, chemical physics, energetics, and other areas of physics and technology. Under Vladimir's leadership, a series of pioneering experimental and theoretical studies of the structural and dynamic properties of plasma-dust crystals was carried out in a wide range of temperatures and pressures. [Extracted from the article]

In this paper the results of studying of the electron temperature of buffer and complex plasmas in mixtures of noble gases (helium + argon) in capacitively coupled radiofrequency (CCRF) discharge are presented. The optical properties of dusty plasma in argon, helium and their mixtures have been studied using optical diagnostic methods. Based on spectral lines of plasma forming gases, the dependence of the electron temperature on gas pressure and discharge power has been determined. The axial distribution of electron temperature in the interelectrode gap has been measured. Measurements have been made using an RF compensated electric probe. The comparison of the experimental results shows that admixture of a small amount of argon to helium leads to a decrease in the electron temperature of buffer plasma. The presence of dust particles in the plasma causes an increase in the electron temperature. [ABSTRACT FROM AUTHOR]

In this paper weakly and strongly non-ideal plasmas are considered. In both cases the equations of state for hydrogen and dusty plasmas were studied on the basis of effective potentials. In the first case the thermodynamic properties for hydrogen plasmas were studied by the method of effective potentials taking into account quantummechanical diffraction, symmetry and screening effects. For strongly non-ideal plasma or dusty plasma the equations of state were considered using radial distribution functions and effective interaction potential, which describes interactions of charged dust grains with dipole moments. [ABSTRACT FROM AUTHOR]

The slowing down of a charged particle beam passing through the dusty plasma with a non‐thermal velocity α‐distribution is studied. By using the Fokker‐Planck collision theory, we derive the deceleration factor and slowing down time and make the numerical analyses. We show that the non‐thermal velocity α‐distributions of the plasma components have a significant effect on the slowing down. With increase of the mean velocity, the deceleration factor increases rapidly, reaches a peak and then decreases gradually. And the entire peak of the deceleration factor moves generally to the right with the increase of the α‐parameter. The slowing down time decreases with the increase of the non‐thermal α‐parameter, and so the slowing down time in the non‐thermal dusty plasma is generally less than that in a Maxwellian one. [ABSTRACT FROM AUTHOR]

Effect of the secondary electron emission (SEE) on the tungsten dust particle in a plasma with super‐extensive electrons is studied in the energy range of 10eV

Ion 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. [ABSTRACT FROM AUTHOR]

Both linear and weakly nonlinear dust‐acoustic (DA) solitons propagation are revisited in the presence of adiabatically trapped‐nonextensive ions. A physically relevant distribution (called Tsallis‐Gurevich ions distribution) is outlined here for the first time. The effect of particle trapping has been taken into account, resulting in a new expression for the ion density. The role a background ion nonextensivity may play on the main proprieties (viz., dispersion relation and soliton's profile) of DA mode, inherent to space dusty plasma, is then analysed. In the q > 1 case, we have shown that as the nonextensive character of trapped ions increases in the plasma, the potential pulse amplitude increases while its width is narrowed. The modifications prompted by the presence of adiabatically trapped‐nonextensive ions on both DA energy and solitary wave's electric field are also analysed. Interestingly, we have found that DA soliton energy increases as the ions evolve far away from their Maxwellian extensive trapping. Also, it is found that, for q > 1, the stronger the inter‐ions correlation, the stronger the electric field. Our investigation, motivated by space and laboratory plasma observations of plasmas containing non‐Maxwellian particles alongside trapped particles, may complement and provide new insight into previously published works dealing with solitary waves in plasma. [ABSTRACT FROM AUTHOR]

Two‐dimensional cluster and pattern formation by charged grains in plasma under external harmonic force and transverse magnetic field is investigated using molecular dynamics simulation. It is found that, as a result of the Yukawa‐like grain‐grain interaction and the external fields, the asymptotic quasistationary state of an initially homogeneous and Maxwellian velocity distributed grain system can be a disk cluster with the grain trajectories having flowery zonal patterns. [ABSTRACT FROM AUTHOR]

Semiconductor nanocrystals, quantum dots (QDs), are known to exhibit the quantum‐confined Stark effect which reveals itself in the shift of their photoluminescence spectra in response to the external electric field. It was, therefore, proposed to use QDs deposited on the microparticle surface for the optical measurement of the charge acquired by the microparticles in low‐temperature plasmas. Another physical process leading to the shift of the photoluminescence spectra of the QDs is heating. Charging of plasma‐facing surfaces is always accompanied by their heating. Thermal balance of a quantum dot residing on the surface of a microparticle immersed in a plasma is considered in this work. It is shown that under periodically pulsed plasma conditions, the spectral shift of the photoluminescence of the quantum dot caused by the oscillations of its temperature becomes undetectable if the effective thermal flux characterizing the thermal contact between the quantum dot and the microparticle exceeds the value ranging from 108$$ {10}^8 $$ to 1010$$ {10}^{10} $$s−1$$ {\mathrm{s}}^{-1} $$ depending on the plasma parameters. If this effective thermal flux exceeds the above‐mentioned values, the entire spectral shift observed during the period of plasma pulsing should be attributed to the quantum‐confined Stark effect due to the microparticle charge. Lower‐boundary estimate for the effective thermal flux for the direct contact between the quantum dot and the microparticle is ∼1012$$ \sim {10}^{12} $$s−1$$ {\mathrm{s}}^{-1} $$. Estimations based on the heat conductivity of ligand‐stabilized nanocrystal arrays yield even higher values of the effective thermal flux ∼1013$$ \sim {10}^{13} $$s−1$$ {\mathrm{s}}^{-1} $$. [ABSTRACT FROM AUTHOR]

Experimental investigations of dusty plasma parameters of a DC glow discharge were performed in helium and argon. In the discharge in helium, at high discharge current dust-free regions (voids) were formed in the center of the dust particles clouds that levitated in the strong electric field of a stratified positive column. In experiments with argon, the dust particles were moved from the center of the discharge tube to the periphery at high discharge current. The behavior of voids formation was investigated for different discharge conditions (sort of gas, discharge pressure and discharge current) and dust particles parameters (particles radii and particles total number). It was shown that it is the ion drag force radial component that leads to the formation of voids in helium and moves the particles to the tube periphery in argon discharge. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The bifurcation types and phase portraits of non‐linear dust ion‐acoustic travelling waves are studied in a dusty plasma comprising warm adiabatic ions, non‐thermal electrons and stationary cold dust species. A dynamical system is derived for the plasma waves evolution, and then the bifurcation response is determined on the equilibrium points‐non‐thermal parameter plane. It is shown that the motion dynamics of travelling waves undergoes a transcritical as well as saddle‐node bifurcations for the critical values of energetic electrons. We indicate that a sudden emergence and transition between solitary waves and non‐linear periodic waves occur at the critical point of transcritical bifurcation. For the saddle‐node bifurcation, we show that both solitary and super‐nonlinear periodic waves disappear, and only a large amplitude periodic wave can propagate in plasma. Further, the coexistence of solitary waves, non‐linear and super‐nonlinear waves are investigated for different values of plasma parameters. The results obtained here could be applicable to different space and astrophysical plasma systems, particularly in Saturn's E‐ring. [ABSTRACT FROM AUTHOR]

Our editorial board is continuing its efforts to provide the best possible service to authors and the plasma physics community. To compensate for those missing topical issues, the editorial board has decided to arrange for separate special topical issues of our journal that will be a valuable resource for plasma physics researchers. As mentioned in the most recent editorial, SP [ sp 4 SP ] sp CPP was among the first journals to broadly offering free open access to a large fraction of authors via the consortium I Projekt DEAL i . SP [ sp 4 SP ] sp We are satisfied that many authors took this opportunity. [Extracted from the article]

Dust ion acoustic waves (DIAWs) are analysed in multi‐component plasmas via reductive perturbation technique comprising inertial ions, (r, q) distributed electrons, and stationary dust by using fluid theory of plasmas. The modified Kadomtsev‐Petviashvili (MKP) equation is obtained for the critical condition at which the quadratic nonlinearity vanishes. Hirota's bilinear formalism is employed, for the first time, to study the two‐soliton solutions of MKP equation in the context of plasma physics. The effects of flatness at low energy (represented by r) and superthermality at high energy (represented by q) of electrons in phase space are investigated for the linear and nonlinear propagation of DIAWs. It is found that the amplitude of the nonlinear DIAW is highest for the flat‐topped distribution, whereas it is lowest for kappa distribution. Using the plasma parameters of Saturn's B‐ring. The estimates are given of the spatial scales over which the MKP solitons form for flat‐topped, kappa, and Maxwellian distributions, respectively. It is also discussed in detail how the presence of dust and non‐Maxwellian electron distributions affect the interaction of MKP solitons in Saturn's B‐ring. In addition, the interaction of a compressive and rarefactive soliton is studied giving results not achievable for KdV and KP equations. [ABSTRACT FROM AUTHOR]

A multispecies magnetized collisional nonthermal plasma system, containing inertial ion species, noninertial electron species following nonthermal κ‐distribution, and immobile dust particles, is considered to examine the characteristics of the dissipative dust‐ion‐acoustic soliton modes, theoretically and parametrically. The electrostatic solitary modes are found to be associated with the low‐frequency dissipative dust‐ion‐acoustic solitary waves (DIASWs). The ion‐neutral collision is taken into account, and the influence of ion‐neutral collisional effects on the dynamics of dissipative DIASWs is investigated. It is reported that most of the plasma medium in space and laboratory are far from thermal equilibrium, and the particles in such plasma system are well fitted via the κ‐nonthermal distribution than via the thermal Maxwellian distribution. The reductive perturbation approach is adopted to derive the damped KdV (dKdV) equation, and the solitary wave solution of the dKdV equation is derived via the tangent hyperbolic method to analyse the basic features (amplitude, width, speed, time evolution, etc.) of dissipative DIASWs. The propagation nature and also the basic features of dissipative DIASWs are seen to influence significantly due to the variation of the plasma configuration parameters and also due to the variation of the supethermality index κ in the considered plasma system. The implication of the results of this study could be useful for better understanding the electrostatic localized disturbances, in the ion length and time scale, in space and experimental dusty plasmas, where the presence of excess energetic electrons and ion‐neutral collisional damping are accountable. [ABSTRACT FROM AUTHOR]

The Landau damping of the dust ion‐acoustic wave (DIAW) in a dusty plasma with non‐extensive distributed components is analysed relying on the kinetic approach. The electron, ion, and dust particles are effectively modelled by the non‐extensive distribution function of the Tsallis statistics. For a collisionless plasma with different values of plasma components indices, the general dispersion relation is achieved, and the non‐extensivity effects on the frequency, as well as the Landau damping of the DIAW, are studied. We show that for q→1, the preliminary results of the Maxwellian plasma are obtained. The decrease of wave damping is achieved by increasing the coefficient q index and the ion‐to‐electron density ratio. The damping rate also increases with an increasing ion‐to‐electron temperature ratio. [ABSTRACT FROM AUTHOR]

In a fluid description, theoretical investigation has been carried out to explore how the presence of two‐temperature electron fluids (hot and cold) influences the characters of dust acoustic solitary waves, double layers, bipolar structures, etc. in a multi‐component dusty plasma, composed of isothermal electrons and ions, along with the negatively charged, cold dusts. A reductive perturbation method is used to derive the well‐known Korteweg‐de Vries (KdV) equation, which describes the basic nature of the dust acoustic solitary waves. Two values of critical ion density exist, which distinguish the regions of compressive and rarefactive solitary waves in parametric space. The critical points directly depend on the densities and temperatures of the electron fluids. With increasing temperature of hot electron fluid, one of the two critical ion densities decreases, and the other one increases. Ultimately, they merge with each other when the temperature of hot electrons reaches a particular value. The amplitude of the dust acoustic soliton gets modified due to the presence of two‐temperature electron fluids. The study is extended further by deriving modified KdV and Gardner equations at the vicinity of critical points. The Gardner equation reveals the existence of double layer and bipolar structures. In these processes, the effects higher‐order nonlinearities are incorporated methodically, by implementing appropriate stretching of the coordinates. Sagdeev's pseudopotential analysis shows that large amplitude rarefactive solitary waves only exist when the corresponding Mach number (M) lies within 1 < M < Mc. The upper bound, Mc increases with the hot electron temperature and cold electron density. The results presented in this investigation are believed to be applicable in the laboratory and astrophysical plasmas. [ABSTRACT FROM AUTHOR]

We investigate the parallel streaming effects on the dispersion characteristics of a kinetic Alfvén wave (KAW) in a low β dusty magnetoplasma. To analyse the influence of streaming ions obeying generalized (r, q) distribution function, hot and magnetized electrons, and mobile charged dust, a theoretical approach has been used for the instability analysis by employing two potential theories. A linear kinetic dispersion relation of Alfvén waves is derived, whose solutions are used to interpret the numerical and analytical results. The solutions of dispersion relation indicate that the characteristics of KAWs are transformed when generalized (r, q) distribution function is employed instead of its Maxwellian counterpart. We also found that the unstable modes have a strong dependence on spectral indices r and q, dust parameters, and plasma β. For the excitation of KAWs, the streaming velocity has been observed to be within the sub‐Alfvén range, whereas when it extends to the super‐Alfvén range, the growth rates are significantly suppressed. The observations further show that an ambient magnetic field and superthermal particles inhibit the growth of an electromagnetic wave to a significant degree and have a stabilizing effect on the wave mode, whereas an increasing concentration of low‐energy particles contributes to enhancing growth rates. [ABSTRACT FROM AUTHOR]

We have performed numerical analysis of the one‐dimensional dynamics of the cylindrical/spherical dust ion acoustic shock waves in unmagnetized dusty plasma consisting of positive ions, immobile dust particles, and nonextensive distributed cold and hot electrons. A multiple‐scale expansion method is used to derive Burgers Equation (BE) and modified Burgers equation (MBE) by including higher order nonlinearity. The basic characteristics of the shock waves have been analysed numerically and graphically for different physical parameters relevant to Saturn' E ring through 2D figures. The parametric dependence of dust ion acoustic shock waves on some plasma parameters nonextensive index, density, and temperature of cold and hot electrons, concentration of dust particles, thermal effects and kinematic viscosity of ions is explored. Furthermore, it is found that the nonplanar geometry effects have an important impact on the establishment of shock waves. The amplitude of the wave decreases faster as one departs away from the axis of the cylinder or centre of the sphere. Such decaying behaviour continues as time progresses. It is also found that an increasing dust concentration decreases the amplitude of the dust ion acoustic shock waves. [ABSTRACT FROM AUTHOR]

A standard nonlinear Schrödinger equation has been established by using the reductive perturbation method to investigate the propagation of electrostatic dust‐acoustic waves, and their modulational instability as well as the formation of localized electrostatic envelope solitons in an electron‐depleted unmagnetized dusty plasma system comprising opposite polarity dust grains and super‐thermal positive ions. The relevant physical plasma parameters (viz., charge, mass, number density of positive and negative dust grains, and super‐thermality of the positive ions, etc.) have rigorous impact to recognize the stability conditions of dust‐acoustic waves. The present study is useful for understanding the mechanism of the formation of dust‐acoustic envelope solitons associated with dust‐acoustic waves in the laboratory and space environments. [ABSTRACT FROM AUTHOR]

The linear and nonlinear properties of dust‐electron acoustic waves (DEAWs) propagating in magnetized, collisionless, dusty plasma system containing inertial cold electrons, Maxwellian hot electrons, nonthermal ions, and arbitrarily (positively or negatively) charged stationary dust are investigated. The reductive perturbation technique is employed to reduce the basic set of fluid equations to the modified Korteweg‐de Vries equation or Ostrovsky's equation, which governs the dynamics of small amplitude DEAWs in a weakly magnetized dusty nonthermal plasma. The approximate analytical as well as numerical solutions reveal that the basic characteristics of DEA nonlinear structures are found to be significantly modified by the key plasma configuration parameters. It is found that the leading compressive or rarefactive solitary wave structure separates from a trailing wave packet during a considerable time under the influence of magnetic field‐induced Lorentz force. [ABSTRACT FROM AUTHOR]

The nonlinear features of dust acoustic waves (DAWs) propagating in a multicomponent dusty plasma with negative dust grains, Maxwellian ions, and double spectral electron distribution (DSED) are investigated. A Korteweg de Vries Burgers equation (KdVB) is derived in the presence of the polarization force using the reductive perturbation technique (RPT). In the absence of the dissipation effect, the bifurcation analysis is introduced and various types of solutions are obtained. One of these solutions is the rarefactive solitary wave solution. Additionally, in the presence of the dissipation effects, the tanh method is employed to find out the solution of KdVB equation. Both of the monotonic and the oscillatory shock structures are numerically investigated. It is found that the correlation between dissipation and dispersion terms participates strongly in creating the dust acoustic shock wave. The limit of the DSED to the Maxwell distribution is examined. The distortional effects in the profile of the shock wave that result by increasing the values of the flatness parameter, r, and the tail parameter, q, are investigated. In addition, it has been shown that the proportional increase in the value of the polarization parameter R enhances in both of the strength of the monotonic shock wave and the amplitude of the oscillatory shock wave. The effectiveness of non‐Maxwellian distributions, like DSED, in several of plasma situations is discussed as well. [ABSTRACT FROM AUTHOR]

A theoretical model is presented to study the characteristics of dust acoustic shock in a viscous, magnetized, rotating dusty plasma at both fast and slow time scales. By employing the reductive perturbation technique, the non‐linear Zakharov–Kuznetsov–Burger (ZKB) equation is derived for both cases when the dust is inactive and dynamic (fast and slow time scales). Both electrons and ions are considered to follow the kappa/Cairns distribution. It is observed that in both cases, i.e. when dust is in the background and active, viscosity plays a key role in dissipation for the propagation of acoustic shock. Magnetic field and rotation are responsible for the dispersive term. Superthermality is found to affect significantly the formation of the shock wave along with viscous nature of plasma, whereas the dust charge affects the non‐linear coefficient of the ZKB equation. The present investigation may be beneficial to the understanding of the rotating plasma, in particular the experiments being carried out. [ABSTRACT FROM AUTHOR]

Evolution of the spatial structure of the massive charged grains in the presence of weak linearly space‐dependent external force in a dusty plasma is studied using molecular dynamics simulation. The interaction among the dust grains in the background electron‐ion plasma is described by a modified Yukawa interaction potential that includes both repulsive and attractive ranges. Evolution of the initially homogeneously distributed dust grains is followed until a quasi‐stationary state is reached. Even though the external force is radially highly asymmetric, the final configuration of the charged grains can be a circular crystal. Still driven by the external force, the grains in the crystal execute synchronized oscillations in the direction of the force. The time needed to reach the quasi‐stationary state decreases with increase of the strength of the external force. [ABSTRACT FROM AUTHOR]

In the present article, we studied the effect of nonthermal electrons on the formation and existence of double‐layer structures in a three‐species plasma consisting of positive ions, nonthermal electrons, and immobile negative dust‐charged grains. Employing the reductive perturbations, a modified Korteweg–de Vries (mKdV) type equation is derived for the dust‐ion‐acoustic waves (DIAWs) bearing nonthermality. We found that both positive and negative polarity shock structures (double layer) can exist such that it switches polarity while changing the dust charge concentrations. However, strong nonthemality favours only rarefactive structures irrespective of the ion temperature. It is also found that increasing the nonthermal electron in the system the width of the double layer is increased; furthermore, the shock structure forms with small dust charge concentration. For small ionic temperature, increasing the nonthermal electrons in the system makes the double layer potential to increase; however, for σ = 1 reverse phenomena occurs. Our results are relevant to the shock observations in Q machine experiments and in the ionospheric regime of the earth. [ABSTRACT FROM AUTHOR]

A theoretical model of propagation of Gaussian and Sine time irradiance of an electromagnetic beam in collisional dusty plasma has been done in the present analysis. It contains equilibrium of dust charge, particle density, and energy of plasma ingredients having charge neutrality. Ionization of neutral particles, recombination of free electrons with ions, adsorption and emission of electrons from dust grain surface, and binary collisions between plasma components are also considered in this treatment. Time varying behaviour of modified electron temperature and collision frequency has been illustrated numerically as a function of dust densities. Also, the comparative analyses of variation of beam waist parameter with the dimensionless length of transmission for both the Gaussian and Sine time irradiance are involved in this model as a function of distinguishable time width, collision frequencies, and dust densities under the condition that the size of dust nebulous is greater than the electrons mean free path for the adsorption on the dust grain surface. The observed results are significant for the applications in industry and astrophysics. [ABSTRACT FROM AUTHOR]

The effects of head‐on collision on dust acoustic (DA) solitary and shock waves in dusty plasma are investigated considering positively charged inertial dust, Boltzmann distributed negatively charged heavy ions, positively charged light ions, and superthermal electrons in the plasma system. The nonlinear Korteweg‐de‐Vries (KdV) Burger equations are derived taking the extended Poincaré‐Lighthill‐Kuo method into account to study the characteristic properties of nonlinearity and production of solitary shock due to collisions. The study reveals that the amplitudes and widths of the DA shock waves are decreasing with increasing viscosity, electron to dust density ratio, and dust to ion temperature ratio, while they are increasing due to the presence of superthermal electrons. The nonlinearity of DA waves are enhanced with increasing density ratio of electron to dust and temperature ratio of dust to ion and electron, respectively, but it is reducing with superthermal electrons. The phase shifts of DA solitary waves are found to decrease with rising superthermality of electrons and increase with the density ratio of electron to dust. [ABSTRACT FROM AUTHOR]

Dust poses a serious threat to tokamak operation and safety. It is important to study the behaviour of dust grains under tokamak's discharge conditions, which depends heavily on their size and charge. Existing simulations mainly address issues on dust grains with radii larger than 1 μm, in which case, the drift effect due to electromagnetic fields can be safely ignored. For nanometer scale dust grains, however, the drift effect becomes significant and a new model based on guiding‐centre system needs to be established. In this work, the NDS has been done under BOUT++ framework. The simulation contains two parts. Part one, NDS evaluates the charging and ablation processes of the dust grains. In the second part, the guiding‐centre orbits of dust particles are tracked in tokamak plasmas, whose parameters are obtained from BOUT++, a highly desirable C++ code package for performing parallel plasma fluid simulations with an arbitrary number of equations in 3D curvilinear coordinates. The orbit of nanodust dynamics is described by guiding centre equations for simplicity, and these equations are numerically solved by conventional fourth‐order Runge Kutta method. Simulations provide results such as trajectories and evolutions of dust particles with different sizes and velocities for different tokamak geometries. Results show tungsten dust grains with a radius of a few nanometers launched from outer midplane will oscillate before totally ablated in C‐Mod. The oscillation in this case is driven by the ion drag force. Larger Nanodust with a radius of 100 nm, on the contrary, cannot be completely constrained by the electromagnetic field. The high plasma temperature and density in the seperatrix region causes severe dust ablation, resulting in total ablation within several ms. [ABSTRACT FROM AUTHOR]

The influence of flow with different strengths, positions, and widths on the structure and dynamics of clusters is studied by two‐dimensional (2D) Langevin molecular dynamics simulations. The particles are confined by a quadratic confining potential. The horizontal position of the system centre, average inter‐particle distance, and coupling parameter are calculated to characterize the effect of changing the strength, position, and width of the flow on the cluster structure. The trajectories, the velocity autocorrelation function, and the mean square displacement are obtained to further uncover the dynamic properties of the 2D dusty plasma system. [ABSTRACT FROM AUTHOR]

A new concept called "configurational temperature" is introduced in the context of dusty plasma, where the temperature of the dust particles submerged in the plasma can be measured directly from the positional information of the individual dust particles and the interaction potential between the dust grains. This method does not require the velocity information of individual particles, which is a key parameter to measure the dust temperature in the conventional method. The technique is initially tested using two‐dimensional (2D) OpenMP parallel molecular dynamics and Monte Carlo simulation and then compared with the temperature evaluated from experimental data. The experiment have been carried out in the Dusty Plasma Experimental (DPEx) device, where a 2D stationary plasma crystal of melamine formaldehyde particles is formed in the cathode sheath of a DC glow discharge argon plasma. The kinetic temperature of the dust is calculated using the standard particle image velocimetry technique at different pressures. An extended simulation result for the three‐dimensional case is also presented, which can be employed for the temperature measurement of a three‐dimensional dust crystal in laboratory devices. [ABSTRACT FROM AUTHOR]

Mutual influence of dust particles and gas discharge plasma was investigated with the help of self‐consistent non‐local kinetic model. Calculations were performed for fixed step‐like radial distributions of the dust particles density, and for self‐consistent distribution calculated by the drift‐diffusion equation. The results show, that the production of electrons and ion occurs mainly outside the dust cloud. In the case of self‐consistent dust particles density distribution, inside the dust cloud the ionization rate is equal to the rate of electron and ion recombination on the dust particles, the radial components of electron and ion fluxes are almost equal to zero, and the radial electric field is expelled from the dust cloud. Presented results can be important for description of the plasma confinement of the dust particles clouds. [ABSTRACT FROM AUTHOR]

A kinetic formulation is developed to investigate low‐frequency dust ion acoustic waves (DIAWs) and dust acoustic waves (DAWs) as well as numerically for a four‐component, collisionless, unmagnetized dusty plasma, using the linearized Vlasov–Poisson model for species obeying the Maxwellian distribution. In particular, the dynamics of low‐frequency DIAWs is investigated by considering two cases. In the first case, ions and positive dust particles are assumed to be dynamically adiabatic while the negative dust particles are static in the background. In second case, the ions are taken adiabatic, while both positive and negative dust particles are static in the background. For DAWs, the ions are assumed to be isothermal, while both positive and negative dust species are considered adiabatic. Electrons are assumed to be isothermal in all cases. The linear characteristics and Landau damping rates for DIAWs and DAWs are investigated with effects of the dust particle concentrations and different temperature ratios. It is noted that for higher values of positive dust concentration, DIAWs (DAWs) are less (more) damped. It is also observed that the damping rate increases (decreases) as Ti approaches Te for DIAWs (DAWs). It is worth adding here that the theoretical results presented here are supported by numerical analyses and illustrations. The relevance of the study to laboratory and cosmic plasmas is also pointed out. [ABSTRACT FROM AUTHOR]

A theoretical model for the effect of dust grains on the self‐filamentation of a Gaussian electromagnetic beam propagating in a fully ionized plasma has been developed by employing the energy balance of the plasma constituents, perturbed electron and ion concentrations, and temperature. In this model, neutral atom ionization, re‐integration and accumulation of electrons and ions, photoelectric emission of electrons from the surface of dust grains, as well as elastic and charging collisions have also been considered. The effective dielectric constant in the presence of dust grains has been constructed. The effect of temporal growth of dust grains on various plasma parameters for different values of the dust density has been explored. The variation of the beam width with the normalized channel of propagation has been observed for distinct dust densities and dust charge states. It is observed that the non‐linearity induced by the effective dielectric constant in the presence of dust grains increases the self‐filamentation of the beam, thus enhancing the effective critical power with the dust density. Some of the outcomes of our approach are in line with experimental observations. These outcomes may be useful for explaining space and laboratory plasma experiments as well as for future studies in complex plasmas. [ABSTRACT FROM AUTHOR]

Complex plasmas are low‐temperature plasmas containing micrometer‐sized particles. They are useful as models for strongly coupled many‐body systems. Since the microparticles are strongly affected by gravity, microgravity experiments with complex plasmas are conducted. Here we report on recent microgravity experiments with the experimental facility PK‐4 performed in parabolic flights. In particular, we discuss electrorheological and demixing experiments and the image analysis tools used. [ABSTRACT FROM AUTHOR]

The vortex motion of a dust cloud was experimentally observed in unmagnetized cogenerated dusty plasma in different experimental parameters. Particle image velocimetry analysis demonstrated that several vortex zones exist in the dust cloud at relatively low pressures (0.06 mbar (or 6 Pa)–0.08 mbar (or 8 Pa)) and low discharge voltages (peak‐to‐peak voltage 540–560 V), whereas in relatively high pressure (0.4 mbar (or 40 Pa)–0.7 mbar (or 70 Pa)) and high discharge voltage (peak‐to‐peak voltage 690–740 V), dust vortices formed in dense dust cloud with background plasma fluctuation. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) Yukawa liquid with an additional screened dipole-dipole interaction is considered in connection with the 2D system of charged dust particles in complex plasmas. Particularly, the sound speed and diffusion in the case the Yukawa interaction potential dominant over the screened dipole-dipole interaction are analysed. Increase in the value of the sound speed and suppression of the super-diffusion due to the additional dipole-dipole interaction are reported. This effect is explained by the stronger inter-particle correlations induced by the additional dipole-dipole interaction. [ABSTRACT FROM AUTHOR]

The nonlinear properties of two dimensional low-frequency electrostatic excitations of charged dust particles (or defects) are studied in a collisionless, unmagnetized dusty plasma. A fully ionized three-component model plasma consisting of kappa distributed electrons, Maxwellian ions, and negatively charged massive dust grains is considered. In this regard, the well known reductive perturbation technique is used to the hydrodynamical equations and the Poisson equation, obtaining the cylindrical Kadomtsev-Petviashvili (CKP) equation. A parametric investigation indicates that the structural characteristics of these nonlinear excitations (width, amplitude) are significantly affected by the plasma nonthermality as well as by the relevant plasma parameters, such as dust concentration and dust temperature. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The formation of clouds of dust particles at the edge of striations of a spherical discharge in ethanol was observed. Periodically, a dust cloud experienced sudden explosion, split into two clouds, which moved in the opposite directions (to the centre of spherical discharge and to the chamber wall). The velocity of the dust cloud was the exponentially decaying function of time with a surprisingly small damping rate as in the case of dissipative dust solitory waves. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Complex (dusty) plasmas are composed of weakly ionised gas and charged microparticles and represent the plasma state of soft matter. Due to the 'heavy' component - the microparticles - and the low density of the surrounding medium, the rarefied gas and plasma, it is necessary to perform experiments under microgravity conditions to cover a broad range of experimental parameters which are not available on ground. The investigations have been performed onboard the International Space Station (ISS) with the help of the 'Plasma Crystal-3 Plus' (PK-3 Plus) laboratory. It was perfectly suited for the formation of large stable liquid and crystalline systems and provided interesting insights into processes like crystallisation and melting, laning in binary mixtures, electrorheological effects due to ac electric fields and projectile interaction with a strongly coupled complex plasma cloud. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Dust particle dynamics is modeled in the so-called Dust Devils (DDs), which are a widespread event on Earth and Mars. We develop methods for the description of dust particle charging in DDs, discuss the ionization processes in DDs, and model charged dust particle motion. Our conclusions are consistent with the fact that DDs can lift a big amount of dust from the surface of a planet into its atmosphere. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In strongly coupled plasmas the diffusion of the particles takes place on a timescale that is long compared to the timescale of oscillations of the particles in the local minima of the potential landscape. The ensuing quasi-stability of the local particle configurations can be quantified by monitoring the changes of the immediate surroundings, i.e. the 'cages', of the particles. Studies of cage correlations are presented here for 2-dimensional Yukawa systems that model dusty plasmas by including the friction exerted on the dust particles by the embedding gaseous environment. We find that the increasing friction enhances the caging time by randomizing the directed motion of the particles. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

A non-self-sustained (NSS) discharge at atmospheric gas pressure containing dust particles is studied. The NSS discharge was controlled by a stationary electron beam with energy up to 120 keV. A numerical model of the NSS discharge is based on the drift-diffusion approach for electrons and ions and self-consistently takes into account effects of the dust particles on the electron and ion densities. The dusty component is described by the number balance equation and the equation of motion for dust particles with allowance for the Stokes force, gravity force and electric force in the cathode sheath. Interaction between dust particles is described in the self-consistent field approximation. It is established that, at a given gas ionization rate and given applied voltage, there is a critical dust particle size above which the levitation condition in the cathode sheath cannot be satisfied. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Complex (dusty) plasmas of micron-sized CeO2 polydisperse particles in dc glow discharges at 77 and ∼ 10 K were experimentally investigated. It was obtained that dust structure in cryogenic gas discharge plasma can be a mixture of two fractions (components) with completely different dust ordering and dynamics. We observed under some specific conditions that fast-moving particles of one component diffuse through another component consisted of dust particles arranged in linear chains (strings). From experimental data analysis particle velocity distribution functions for each dust component were obtained. The possible nature of two-component dust structure formation was discussed. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The problem of calculation of the electric charge of dust particles in a plasma is considered from different points of view. At first the charging of polarizable dust particles is studied within the orbital motion limited approach. Secondly, the plasma electrodynamics is applied to show that the electric charge of a dust particle is determined by the normal component of the dielectric displacement vector near the grain surface rather than the normal component of the electric field strength. And, finally, the chemical model, initially proposed for determination of partially ionized plasma composition, is demonstrated to be very productive in evaluating the electric charge of the dust component. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The possibility of charged particles trapped by the linear quadrupole Paul trap to form an ensemble with strong Coulomb interaction at atmospheric pressure has been experimentally shown. The ordered structure could confine particles of different sizes and charges. Stable clouds of thousands of oxide aluminum particles with sizes of 0.5÷65 microns were observed in the linear trap with electrodes placed 30 mm apart. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]