The Effects of Inhomogeneity and Adiabatic Dusty Charge Fluctuation on Solitary Waves

Using the perturbation method, the modified variable coefficient Kadomtsev-Petviashvili (MKP) equation governing nonlinear dust acoustic solitary waves is for the first time derived with the combined effects of adiabatic dust charge fluctuation and higher-order transverse perturbation in inhomogeneous dusty plasmas due to the spatial gradients of dust charge and plasma densities. The MKP equation is reduced to the standard Kadomtsev-Petviashvili (KP) equation. The numerical results show that inhomogeneity has strong influence on the nonlinear properties of dust acoustic solitary waves.     

Transverse Instability of Dust-Acoustic Solitary Waves in Magnetized Dusty Plasmas

we theoretically investigated the transverse instability of three-dimensional(3D)dust-acoustic solitary waves in a magnetized dusty plasma.First,a 3D nonlinear ZakharovKuznetsov(ZK)equation,which can be used to describe the time-evolution of dust-acoustic solitary waves in magnetized dusty plasmas,is derived by using the reductive perturbation method.Second,we established a numerical scheme to study the transverse instability of the solitary waves described by the ZK equation.It was found that both stable and unstable solitary waves exist.     

Dusty Sheaths in Magnetized Plasmas

Parameters of self-consistent magnetized dusty sheaths are investigated using computer simulations of a temporal evolution of one-dimensional slab plasma with dust particles. The evolution is caused by a collection of electrons and ions by both a wall (electrode) and dust particles, which are initially immersed into plasma and distributed in front of the electrode. Obtained results show the existence of oscillations of a self-consistent potential in magnetized dusty sheaths including boundary potentials. Dust particles weaken magnetized sheaths and create additional sheaths close to a boundary of dust particles. The magnetic field does not influence on the dust particle charge.     

Breathing Modes in Dusty Plasma

Acoustic breathing modes of dusty plasmas have been investigated in a cylindrical system with an axial symmetry. The linear wave solution and a “dispersion” relation were derived.It was found that in an infinite area, the mode is reduced to a “classical” dust acoustic wave in the region away from the center. If the dusty plasma is confined in a finite region, however, the breathing (or heart-beating) behavior would be found as observed in many experiments.     

Propagation characteristics of microwaves in dusty plasmas with multi-collisions

In this study, we consider three main collisions in dusty plasmas and investigate the effects of dust grains on the propagation of electromagnetic(EM) waves through uniform, unmagnetized and weakly ionized dusty plasma. The Drude model is improved to describe the dielectric property of dusty plasmas, which accounts for collisions including electron–molecule, electron–ion, and electron–dust particles. Based on the improved Drude model, the propagation characteristics of microwaves in dusty plasmas have been numerically calculated and studied.The results show that the propagation characteristics of microwaves through dusty plasmas are different from those through normal plasmas. The effects of dust density and size are mainly studied. Numerical results indicate that the momentum transfer between electrons and dust grains makes more energy loss. The dust density and dust size have a similar influence on EM wave propagation, resulting in less transmission and more absorption.     

FDTD Simulation on Terahertz Waves Propagation Through a Dusty Plasma

The frequency dependent permittivity for dusty plasmas is provided by introducing the charging response factor and charge relaxation rate of airborne particles. The field equations that describe the characteristics of Terahertz(THz) waves propagation in a dusty plasma sheath are derived and discretized on the basis of the auxiliary differential equation(ADE) in the finite difference time domain(FDTD) method. Compared with numerical solutions in reference, the accuracy for the ADE FDTD method is validated. The reflection property of the metal Aluminum interlayer of the sheath at THz frequencies is discussed. The effects of the thickness, effective collision frequency, airborne particle density, and charge relaxation rate of airborne particles on the electromagnetic properties of Terahertz waves through a dusty plasma slab are investigated.Finally, some potential applications for Terahertz waves in information and communication are analyzed.     

Dust Acoustic Compressive Waves in a Warm Dusty Plasma Having Non-Thermal Ions and Non-Isothermal Electrons

In this article an investigation is presented on the properties of dust acoustic(DA)compressive solitary wave propagation in an adiabatic dusty plasma,including the effect of nonthermal positive and negative ions and non-isothermal electrons.The reductive perturbation method has been employed to derive the lower degree modified Kadomtsev-Petviashivili(mK-P),3D Schamel-Korteweg-de-Vries equation or modified Kadomtsev-Petviashivili(mK-P) equations for dust acoustic solitary waves in a homogeneous,unmagnetized and collisionless plasma whose constituents are non-isothermal electrons,singly charged positive and negative non-thermal ions and massive charged dust particles.The stationary analytical solutions of the lower degree mK-P and mK-P equations are numerically analyzed,where the effect of various dusty plasma constituents on DA solitary wave propagation is taken into account.It is observed that both the ions in dusty plasma play a key role in the formation of DA compressive solitary waves,and also the ion concentration and non-isothermal electrons control the transformation of the compressive potentials of the waves.     

Propagation of Ion Solitary Pulses in Dense Astrophysical Electron-Positron-Ion Magnetoplasmas

In this paper,we theoretically investigate the existence and propagation of low amplitude nonlinear ion waves in a dense plasma under the influence of a strong magnetic field.The plasma consists of ultra-relativistic and degenerate electrons and positrons and non-degenerate cold ions.Firstly,the appearance of two distinct linear modes and their evolution is studied by deriving a dispersion equation with the aid of Fourier analysis.Secondly,the dynamics of low amplitude ion solitary structures is investigated via a Korteweg-de Vries equation derived by employing a reductive perturbation method.The effects of various plasma parameters like positron concentration,strength of magnetic field,obliqueness of field,etc.,are discussed in detail.At the end,analytical results are supplemented through numerical analysis by using typical representative parameters consistent with degenerate and ultra-relativistic magnetoplasmas of astrophysical regimes.     

Numerical Simulation of Tripolar Vortex in Dusty Plasma with Sheared Flow and Sheared Magnetic Field

This article presents a study we have made of one class of coherent structures of the tripolar vortex. Considering the sheared flow and sheared magnetic field which are common in the thermonuclear plasma and space plasma, we have simulated the dynamics of the tripolar vortex. The results show that the tripolar vortex is largely stable in most cases, but a strongly sheared magnetic field will make the structure less stable, and lead it to decays into single vortices with the large space scale. These results are consistent with findings from former research about the dipolar vortex.     

Dust Acoustic Shock Waves with Non-Thermal and Vortex-Like Ions in Dusty Plasma

A rigorous investigation is presented on the propagation characteristics of non-linear dust acoustic(DA)waves in an unmagnetized dusty plasma system containing non-thermal and vortex-like ions and Maxwellian electrons under the effect of a fluctuating charged dust fluid.The three-dimensional(3D)Burgers'equation and a new form of a lower degree modified 3D Burgers'equation with their analytical solutions are derived to study the features of shock waves in such plasmas.The effect of the population of non-thermal ions,the vortex-like ion parameter as well as the temperature ratios of ions and electrons on the evolution of shock waves in the presence of dust charge fluctuation is presented.This theoretical investigation might be effectively utilized to unveil the nature of many astrophysical plasma environments(Saturn's spokes etc.)where such plasmas are reported to have existed.     

Characteristics of Langmuir Probe in Low Temperature, Weakly Magnetized Plasmas

The systematic Langmuir probe measurements for a weakly magnetized plasma have been carried out in the Linear Magnetized Plasma Device for different magnetic fields. By comparing the ion current density of probes with different sizes, the sheath thickness can be evaluated. It is found that while the ratio of cylindrical probe‘s dimension to ion Larmor radius is not more than 2, the model of probe for non-magnetized plasma is still applicable.     

Dispersion Relation of Linear Waves in Quantum Magnetoplasmas

The quantum magnetohydrodynamic(QMHD) model is applied in investigating the propagation of linear waves in quantum magnetoplasmas. Using the QMHD model, the dispersion equation for quantum magnetoplasmas and the dispersion relations of linear waves are deduced.Results show that quantum effects affect the propagation of electron plasma waves and extraordinary waves(X waves). When we select the plasma parameters of the laser-based plasma compression(LBPC) schemes for calculation, the quantum correction cannot be neglected. Meanwhile,the corrections produced by the Fermi degeneracy pressure and Bohm potential are compared under different plasma parameter conditions.     

Solitary kinetic Alfvén waves in dense plasmas with relativistic degenerate electrons and positrons

Propagation of solitary kinetic Alfvén waves (KAWs) is investigated in small but finiteβ (particle-to-magnetic pressure ratio) collisionless dense plasma whose constituents are nondegenerate warm ions, and relativistic degenerate electrons and positrons. Through the use of reductive perturbation technique, Kortweg–de Vries equation is derived to obtain small amplitude localized wave solution of KAWs. The effects of plasmaβ, positron concentration, electron relativistic degeneracy parameter, ion thermal temperature and obliqueness parameter on solitary KAWs are studied. The results of this theoretical investigation are aimed at elucidating characteristics of kinetic Alfvén solitary waves in relativistic degenerate e–p–i plasmas found in dense astrophysical objects specifically neutron stars and white dwarfs.     

Faraday angle of Linearly Polarized Waves along Magnetic Field in Magnetized Collisional Plasmas

In magnetized collisional plasmas, owing to the differences between attenuations of left- and right-handed polarized waves, the Faraday rotation angle differs from that in collisionaless plasmas. In this paper, the attenuation rates of left- and right-handed polarized waves are analyzed, and the Faraday angle is expressed by the real and imaginary parts of refractive index of the magnetized plasma, with clear physics meaning. Furthermore, the dependence of Faraday angle on collision frequency is calculated and discussed.     

Some studies on transient behaviours of sheath formation in dusty plasma with the effect of adiabatically heated electrons and ions

Based on quasipotential analysis, a plasma sheath is studied through the derivation of the Sagdeev potential equation in dusty plasma coexisting with adiabatically heated electrons and ions. Salient features as to the existence of sheaths are shown by solving the Sagdeev potential equation through the Runge–Kutta method, with appropriate consideration of adiabatically heated electrons and ions in the dynamical system. It has been shown that adiabatic heating of plasma sets a limit to the critical dust speed depending on the densities and Mach number, and it is believed that its role is very important to the sheath. One present problem is the contraction of the sheath region whereby dust grains levitated into the sheath lead to a crystallization similar to the formation of nebulons and are compressed to a larger chunk of the dust cloud by shrinking of the sheath. Our overall observations advance knowledge of sheath formation and are expected to be of interest in astroplasmas.     

The Excitation of the Low-Frequency Electromagnetic Wave in Dusty Plasma with Vortex Flows

The Excitation of Alfven wave in dusty plasma with vortex flows is investigated. The coupled equations for density and electromagnetic potential of dusty plasma with vortex-flow were obtained. The stability and amplitude behavior were studied both analytically and numerically. Using a non-modal method, it was found that the presence of dust can suppress the growth of the instability which can also be affected by the vortex eccentricity.     

Nonlinear Dust Acoustic Waves in a Magnetized Dusty Plasma with Trapped and Superthermal Electrons

In this work, the effects of superthermal and trapped electrons on the oblique propa- gation of nonlinear dust-acoustic waves in a magnetized dusty （complex） plasma are investigated. The dynamic of electrons is simulated by the generalized Lorentzian （k） distribution function （DF）. The dust grains are cold and their dynamics are simulated by hydrodynamic equations. Using the standard reductive perturbation technique （RPT） a nonlinear modified Korteweg-de Vries （mKdV） equation is derived. Two types of solitary waves; fast and slow dust acoustic solitons, exist in this plasma. Calculations reveal that compressive solitary structures are likely to propagate in this plasma where dust grains are negatively （or positively） charged. The properties of dust acoustic solitons （DASs） are also investigated numerically.     

A Method to Construct Plasma with Nonlinear Density Enhancement Effect in Multiple Internal Inductively Coupled Plasmas

A method is proposed to built up plasma based on a nonlinear enhancement phenomenon of plasma density with discharge by multiple internal antennas simultaneously. It turns out that the plasma density under multiple sources is higher than the linear summation of the density under each source. This effect is helpful to reduce the fast exponential decay of plasma density in single internal inductively coupled plasma source and generating a larger-area plasma with multiple internal inductively coupled plasma sources. After a careful study on the balance between the enhancement and the decay of plasma density in experiments, a plasma is built up by four sources, which proves the feasibility of this method. According to the method, more sources and more intensive enhancement effect can be employed to further build up a high-density, large-area plasma for different applications.     

电子回旋波在非圆截面托卡马克等离子体中的传播与功率沉积

通过求解等离子体平衡方程、波迹方程和准线性Fokker-Planck方程,数值模拟了电子回旋(EC)波在非圆截面托卡马克等离子体中的传播轨迹和功率沉积。模拟结果表明:当EC波从顶部发射时,相比于圆截面的EC波波迹,非圆截面的波迹会向等离子体弱场侧偏移,增大等离子体中心电子密度,波迹也会偏向弱场侧,相应的波功率沉积有所降低;当EC波O模从中平面弱场侧发射时,随着平行折射率的增大,波迹弯曲幅度变大,增大到一定数值时会折回弱场侧穿出,波功率沉积随极向发射角的增大而降低,环向发射角约取10°时,波功率沉积达到最大。     

Observation of Vortex Patterns in a Magnetized Dusty Plasma System

Vortex patterns of dust particles have been observed in a magnetized dusty plasma system. The formation mechanism of two-dimensional （2D） vortex patterns has been investigated by analysing the forces acting on dust particles and molecular dynamics （MD） simulations in a 2D confined magnetized dusty plasma. It has been found that with a weak confining electric field and a strong magnetic field, the particles＇ trajectories will form a vortex shape. The simulation results agree with our experimental observations. In our experiments, vortex patterns can be induced via circular rotation of particles by changing the rf （radio-frequency） power in a magnetized dusty plasma.