Stationary Dust Research Articles

Arbitrary amplitude dust–ion acoustic solitary structures in electronegative plasma

In the present study existence domains of large amplitude dust–ion acoustic (DIA) solitary structures are analyzed in an unmagnetized and collisionless, electronegative plasma containing inertial positive and negative ions, inertialess superthermal electrons with two different temperatures and negatively charged stationary dust. Using the Sagdeev pseudopotential technique, the energy-balance equation has been derived and the critical values (lower and upper limits) of the Mach number are also determined. The effect of different physical parameters has been analyzed for the formation of these nonlinear structures. Also the critical values of different physical parameters have been determined to establish parametric regimes for the existence of positive/negative potential DIA solitary structures.

Microphysics of liquid complex plasmas in equilibrium and non-equilibrium systems

The dynamic evolution of the microscopic structure of solid and liquid phases of complex plasmas is studied experimentally and by means of molecular dynamics (MD) simulations. In small finite systems, the cooperative motion can be described in terms of discrete modes. These modes are studied with different experimental approaches. Using diffuse scattered laser light, applying laser tweezer forces to individual particles, and periodic laser pulses, the excitation of modes is investigated. The instantaneous normal mode analysis of experimental data from two-dimensional liquid clusters gives access to the local dynamics of the liquid phase. Our investigations shed light on the role of compressional and shear modes as well as the determination of diffusion constants and melting temperatures in finite systems. Special attention is paid to hydrodynamic situations with a stationary inhomogeneous dust flow. MD simulations allow to study the collective motion in the shell of nearest neighbors, which can be linked to smooth and sudden changes of the macroscopic flow. Finally, the observed micro-motion in all situations above allows to shed light on the preference of shear-like over compressional motion in terms of a minimized potential energy and a dynamic incompressibility.

Ion acoustic solitons in magnetized collisional non-thermal dusty plasmas

The oblique propagation of ion-acoustic solitary waves (IASWs) is considered, in a magnetized non-thermal collisional dusty plasma, composed of non-Maxwelian κ-distributed electrons, inertial ions, and stationary dust. The reductive perturbation approach is adopted to derive the damped Korteweg de-Vries (dKdV) equation, and the dissipative oblique ion-acoustic wave properties are investigated in terms of different key plasma parameters via the numerical solution of the dKdV equation. The collisional effect, describing the ion-neutral collision in the plasma, is taken into account, and seen to influence the dynamics of IASWs significantly. The basic features of IASWs are observed to modify, and the polarity of the wave is seen to change due to the variation of dust to that of ion number density and also due to the variation of the supethermality index κ in the considered plasma system.

Ion acoustic solitary structures in a magnetized nonthermal dusty plasma

The Sagdeev potential technique has been used to investigate the arbitrary amplitude ion acoustic solitary structures in a collisionless magnetized dusty plasma consisting of negatively charged static dust grains, adiabatic warm ions and nonthermal electrons. The present system supports both positive and negative potential solitary waves, the coexistence of solitary waves of both polarities, and negative potential double layers. The system does not support any positive potential double layer. Although the system supports negative potential double layers, these double layer solutions cannot restrict the occurrence of all solitary structures of same polarity. In fact, there exists a parameter regime for which the negative potential double layer is unable to restrict the occurrence of negative potential solitary waves, and in this region of the parameter space, there exist negative potential solitary waves after the formation of a negative potential double layer. Consequently, negative potential supersolitons have been observed and the Mach number M corresponding to a negative potential supersoliton is restricted by the inequality MNPDL < M < Mcr, but this supersoliton structure reduces to a conventional solitary wave of same polarity if M ≥ Mcr, where MNPDL is the Mach number corresponding to a negative potential double layer and Mcr is a critical value of M. Thus, we have seen a transition process of negative potential solitary structures, viz., soliton → double layer → supersoliton → soliton. Different solitary structures have been investigated with the help of compositional parameter spaces and the phase portraits of the dynamical system describing the nonlinear behaviour of ion acoustic waves. The mechanism of transition of a negative potential supersoliton to a conventional soliton after the formation of a double layer of same polarity has been discussed with the help of phase portraits.

Effects of dust polarity and nonextensive electrons on the dust-ion acoustic solitons and double layers in earth atmosphere

Propagation of dustion acoustic solitary waves (DIASWs) and double layers is discussed in earth atmosphere, using the Sagdeev potential method. The best model for distribution function of electrons in earth atmosphere is found by fitting available data on different distribution functions. The nonextensive function with parameter q=0.58 provides the best fit on observations. Thus we analyze the propagation of localized waves in an unmagnetized plasma containing nonextensive electrons, inertial ions, and negatively/positively charged stationary dust. It is found that both compressive and rarefactive solitons as well as double layers exist depending on the sign (and the value) of dust polarity. Characters of propagated waves are described using the presented model.

Oblique Interaction of Dust-ion Acoustic Solitons with Superthermal Electrons in a Magnetized Plasma

The oblique interaction between two dust-ion acoustic (DIA) solitons travelling in the opposite direction, in a collisionless magnetized plasma composed of dynamic ions, static dust (positive/negative) charged particles and interialess kappa distributed electrons is investigated. By employing extended Poincare–Lighthill–Kuo (PLK) method, Korteweg–de Vries (KdV) equations are derived for the right and left moving low amplitude DIA solitons. Their trajectories and corresponding phase shifts before and after their interaction are also obtained. It is found that in negatively charged dusty plasma above the critical dust charged to ion density ratio the positive polarity pulse is formed, while below the critical dust charged density ratio the negative polarity pulse of DIA soliton exist. However it is found that only positive polarity pulse of DIA solitons exist for the positively charged dust particles case in a magnetized nonthermal plasma. The nonlinearity coefficient in the KdV equation vanishes for the ne...

Dust charging and levitating in a sheath of plasma containing energetic particles**Project supported by the National Natural Science Foundation of China (Grant No. 11475223), the National Magnetic Confinement Fusion Science Program of China (Grant No. 2015GB101003), and the JSPS-NRF-NSFC A3 Foresight Program in the field of Plasma Physics (Grant Nos. 11261140328 and 2012K2A2A6000443).

The structure of the sheath in the presence of energetic particles is investigated in the multi-fluid framework. Based on the orbital motion limited (OML) theory, the dust grain charging inside the sheath of plasma containing energetic particles is examined for the carbon wall, and then the effect of the energetic particles on the stationary dust particle inside the sheath is discussed through the trapping potential energy. It is found that with the increase of energetic ion concentration or energy, the size of dust staying in levitation equilibrium decreases and the levitating position is much closer to the wall. In the case of deuterium ions as energetic ions, the bigger dust particle can be trapped by the sheath than in the case of hydrogen ions as energetic ions. When the energetic electron component is present, the levitating position of dust particle in the sheath depends strongly on the energetic electron. The levitating dust particle is closer to the wall as the energetic electron energy or concentration is increased. In addition, with the increase of temperature of thermal background ion, the size of dust particle trapped by the sheath decreases and the levitating positions of dust particles with the same size radius inside the sheath move toward the wall. Our results can be helpful in investigating the property of the sheath where the energetic particle component is present.

Exact Traveling Wave Solutions of Further Modified Korteweg–De Vries Equation in Multicomponent Plasma

Using the hydrodynamic equations of positive and negative ions, Boltzmann electron density distribution for degenerate electron pressure, and Poisson equation with stationary dust, a further modified Korteweg–Vries equation is derived for small but finite amplitude dust-ion-acoustic waves. ‘\(G'/G\)’ method is used to obtain a new class of solutions. The effects of physical parameters on astrophysical compact objects, and thus the nonlinear solitary and shock structures are examined corresponding to traveling waves.

The tanh solution of KdV-B equation in four-component quantum plasma by taking into account dust charge variation

Nonlinear propagation of quantum dust-ion acoustic shock and solitary waves in an unmagnetized and collisionless four-component plasma medium containing inertialess quantum electrons and positrons, and also classical ions and stationary negative dust grains, which are affected by dust charge variations and viscosity of ions, are investigated using a quantum hydrodynamic model by employing the tanh method. The Korteweg–de Vries-Burgers and the Korteweg–de Vries equations indicate the behavior of shocks and solitons in this plasma model, respectively. Consideration of the dust charge variation requires the evaluation of charging currents. These currents are determined with the orbit limited motion theory and using the corresponding velocity distribution function. In the following, the effects of chemical potential and the density of dust grains on the structure of oscillatory and monotonic shock waves and solitary waves are investigated. The current study extends our understanding of the characteristics of quantum nonlinear structures in superdense astrophysical systems, inertial confinement fusion plasmas, and ultrasmall micro- and nano- electronic devices.

Solar wind interaction with dusty plasmas produces instabilities and solitary structures

It is pointed out that the solar wind interaction with dusty magnetospheres of the planets can give rise to purely growing instabilities as well as nonlinear electric field structures. Linear dispersion relation of the low frequency electrostatic ion-acoustic wave (IAW) is modified in the presence of stationary dust and its frequency becomes larger than its frequency in usual electron ion plasma even if ion temperature is equal to the electron temperature. This dust-ion-acoustic wave (DIAW) either becomes a purely growing electrostatic instability or turns out to be the modified dust-ion-acoustic wave (mDIAW) depending upon the magnitude of shear flow scale length and its direction. Growth rate of shear flow-driven electrostatic instability in a plasma having negatively charged stationary dust is larger than the usual D’Angelo instability of electron-ion plasma. It is shown that shear modified dust ion acoustic wave (mDIAW) produces electrostatic solitons in the nonlinear regime. The fluid theory predicts the existence of electrostatic solitons in the dusty plasmas in those regions where the inhomogeneous solar wind flow is parallel to the planetary or cometary magnetic field lines. The amplitude and width of the solitary structure depends upon dust density and magnitude of shear in the flow. This is a general theoretical model which is applied to dusty plasma of Saturn’s F-ring for illustration.

Nonlinear shock structures with contributions of arbitrary dust size distribution and nonadiabatic charge fluctuation in dusty plasmas

The nonlinear characteristics of shock structures have been investigated in dusty plasma consisting of inertialess Boltzmann distributed electrons, nonthermally distributed ions, and stationary dust grains with nonadiabatic charge fluctuation and arbitrary dust size distribution in present work. A Korteweg–de Vries (KdV) Burgers equation governing the dust acoustic shock structures is obtained by Reductive Perturbation Method. The relevance of shock waves’ evolution to the dust size distribution and nonadiabatic charge fluctuation is illustrated both analytically and numerically. The numerical results show that dust size distribution, and nonadiabatic charge fluctuation have strong common influence on the propagation of shock structures.

Modulational instability of electrostatic waves in a magnetized dusty plasma with kappa distributed electrons

The modulational instability of dust-ion acoustic wave (DIAW) and dust-ion cyclotron wave (DICW) is investigated in a magnetized plasma containing static dust particles. The static dust particles can be positively or negatively charged, while ions are taken to be dynamic and inertialess electrons follow the kappa distribution in a magnetized dusty plasma. The nonlinear Schrödinger equation is derived to study the amplitude modulation of obliquely propagating electrostatic waves in a magnetized dusty plasma using the Krylov-Bogoliubov-Mitropolsky method. The dispersive and nonlinear coefficients, i.e., P and Q of nonlinear Schrödinger equation, are obtained which depend on the dust charge concentration, the magnetic field intensity, dust charge polarity, angle of wave propagation, and spectral index kappa for the nonthermal electrons. The modulationally stable and unstable regions of DIAW and DICW are investigated numerically, and the illustration of contour plots of product PQ with wave propagation angle θ and critical wave number kc is also presented. It is found that DIAW and DICW become modulationally unstable at low values of wave number k for negatively charged dust particles in comparison with positively charged dust particles or without dust particles case in a magnetized plasma. The stable region for DIAW, whose wave frequency now depends also on wave propagation angle in a magnetized plasma, is found to be increased in comparison with the unmagnetized plasma case. The observations and existence of positively and negatively charged dust particles in different regions of space plasmas and in laboratory experiments are also pointed out.

Comparative study of dust ion acoustic Korteweg–de Vries and modified Korteweg–de Vries solitons in dusty plasmas with variable temperatures

In this plasma model, consisting of ions and electrons with pressure variations in both the components in the presence of stationary dust, both compressive and rarefactive Korteweg–de Vries (KdV) solitons of interesting character are established. Based on high dust charge, characteristics of soliton growth are found to be amplified for various pairs of ion and electron streaming speeds. It is noteworthy to mention that for some pairs of ion and electron initial streaming speeds, only compressive KdV solitons with either decreasing or increasing growth are shown to reflect. Contrary to this, for some other pairs of ion and electron streaming speeds, the amplitudes of both rarefactive and compressive solitons are seen to be produced, changing from rarefactive to compressive growth. At the stationary background of the massive dust particles, the lighter particles suffer appreciable initial drifts (backwards streaming) which characteristically change the growth of solitons. For inclusion of higher-order nonlinearity, only compressive modified Korteweg–de Vries (MKdV) solitons of much higher amplitude are found to exist whereas for the same set of parameter values both compressive and rarefactive KdV solitons are found to exist. Smaller values of electron streaming speed are seen to produce high amplitude MKdV solitons. We also observe that due to higher-order nonlinearity, the nonlinear monotonic growth of amplitudes of MKdV solitons is supported by the almost equal streaming speed pairs of ions and electrons for relatively small values of$Z_{d}$, where$Z_{d}$is the number of charges in a dust particle

All static charged dust spheres in general relativity

Exact solutions for distributions of static charged dust in general relativity are sought in a systematic way in curvature coordinates. An algorithm is proposed to identify all dust spheres subject to carrying out a single integration after specifying a gravitational potential. It is argued that charged dust distributions are described by metrics that are inherently singular. The algorithm is illustrated for a simple case that generalises several known cases treated historically. Further new dust models are generated by specifying the other gravitational potential and well known metric Ansätze, namely, the generalised Schwarzschild and Finch–Skea prescriptions are treated.

Drift wave driven double layers in an inhomogeneous magnetized plasma in the presence of stationary dust

The properties of drift wave driven Double Layers (DLs) in an inhomogeneous magnetized plasma with density and temperature inhomogeneity in the presence of stationary dust are investigated. An extended Korteweg–de Vries like equation is derived, and its solution in the form of DLs is obtained by employing proper boundary conditions. It is noticed that the amplitude and steepness of drift wave driven DLs change with the variation in the dust concentration and temperature inhomogeneity. It is also seen that the DLs in this inhomogeneous plasma are rarefactive in nature if structures move faster than the drift speed. For illustration, the results are applied in the F-region of Earth's ionosphere.

Development of high-resolution dynamic dust source function - A case study with a strong dust storm in a regional model

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 02–03 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events.

Driving force for a nonequilibrium phase transition in three-dimensional complex plasmas

An example of the non-equilibrium phase transition is the formation of lanes when one kind of particle is driven against the other. According to experimental observation, lane formation in binary complex plasmas occurs when the smaller particles are driven through the stationary dust cloud of the larger particles. We calculate the driving force acting on a probe particle that finds itself in a quiescent cloud of particles in complex plasma of the low-pressure radio frequency discharge under microgravity conditions. It is shown that the nonzero driving force is a result of the dependence of the ion mean free path on the particle number density. If this effect is properly included in the model of similar complex plasmas, then one arrives at the driving force that changes its sign at the point where the probe and the dust particles have equal radii. If the probe is smaller than the dust particle, then the driving force is directed toward the discharge center and vice versa, in accordance with the experiment. The obtained results can serve as the ansatz for future investigation of the lane formation in complex plasmas.

Nonlinear dust-ion acoustic periodic travelling waves in a magnetized plasma with two temperature superthermal electrons and stationary charged dust grains

In this research, the nonlinear propagation of dust-ion acoustic (DIA) periodic travelling waves in a dusty plasma consisting of cold ions, stationary charged dust grains, and two temperature superthermal electrons is theoretically studied. A nonlinear Zakharov-Kuznetsov equation, which describes nonlinear dust-ion acoustic waves, is derived using a reductive perturbation method. Furthermore, the bifurcation theory has been employed to study the nonlinear propagation of DIA periodic travelling wave solutions. In the proposed model, the co-existence of both compressive and rarefactive DIA periodic travelling waves are found. The numerical investigations illustrate that the characteristics of nonlinear DIA periodic travelling waves strongly depend on the temperature ratio, both the concentration and the superthermality of cold electrons, the ion cyclotron frequency, the direction cosines of wave vector k along z axis, and the concentration of dusty grains. The present investigation can help in better understanding of nonlinear DIA periodic travelling waves in astrophysical environments with two temperature superthermal electrons such as Saturn's magnetosphere.

Dust ion acoustic solitary structures in the presence of isothermal positrons

The Sagdeev potential technique has been employed to study the dust ion acoustic solitary waves and double layers in an unmagnetized collisionless dusty plasma consisting of negatively charged static dust grains, adiabatic warm ions, isothermally distributed electrons, and positrons. A computational scheme has been developed to draw the qualitatively different compositional parameter spaces or existence domains showing the nature of existence of different solitary structures with respect to any parameter of the present plasma system. The present system supports both positive and negative potential double layers. The negative potential double layer always restricts the occurrence of negative potential solitary waves, i.e., any sequence of negative potential solitary waves having monotonically increasing amplitude converges to a negative potential double layer. However, there exists a parameter regime for which the positive potential double layer is unable to restrict the occurrence of positive potential solitary waves. As a result, in this region of the parameter space, there exist solitary waves after the formation of positive potential double layer, i.e., positive potential supersolitons have been observed.

Dust ion acoustic solitary structures in presence of nonthermally distributed electrons and positrons

The purpose of this paper is to extend the recent work of Paul and Bandyopadhyay [Astrophys. Space Sci. 361, 172 (2016)] on the existence of different dust ion acoustic solitary structures in an unmagnetized collisionless dusty plasma consisting of negatively charged static dust grains, adiabatic warm ions, nonthermal electrons, and isothermal positrons in a more generalized form by considering nonthermal positrons instead of isothermal positrons. The present system supports both positive and negative potential double layers, coexistence of solitary waves of both polarities, and positive potential supersolitons. The qualitative and quantitative changes in existence domains of different solitary structures, which occur in the presence of nonthermal positrons, have been presented in comparison with the results of Paul and Bandyopadhyay [Astrophys. Space Sci. 361, 172 (2016)]. The formation of supersoliton structures and their limitations has been analyzed with the help of phase portraits of the dynamical system corresponding to the dust ion acoustic solitary structures. Phase portrait analysis clearly indicates a smooth transition between solitons and supersolitons.