Effect of dust charge variation on dust—acoustic solitary waves in a magnetized two—ion—temperature dusty plasma

The effect of dust charge variation on the dust-acoustic solitary structures is investigated in a warm magnetized two-ion-temperature dusty plasma consisting of a negatively and variably charged extremely massive dust fluid and ions of two different temperatures. It is shown that the dust charge variation as well as the presence of a second component of ions would modify the properties of the dust-acoustic solitary structures and may exite both dust-acoustic solitary holes (soliton waves with a density dip) and positive solitons (soliton waves with a density hump).     

The instability of electrostatic wave in a magnetized dusty plasma with nonadiabatic dust charge fluctuation

The effects of external magnetized field and nonadiabatic dust charge fluctuation on instability of wave incorporating the nonthermally distributed ions and the temperatures of ion and dust in dusty plasmas are investigated. A linear dispersion relation is obtained. The numerical results show that the external magnetized field, fast ions and nonadiabatic dust charge fluctuation have strong influence on the frequency and the damping of wave.     

The effects of dust temperature and the dust charge variation in a dusty plasma with vortex—like ion distribution

By considering both the dust temperature and the dust charge variation in dusty plasma with vortex-like ion distribution, we obtained a modified Korteweg－de Vries equation. It indicates that the effect of dust charge variation can cause the one-dimensional soliton amplitude to become larger, and the dust temperature can cause the soliton amplitude to become larger as well. Moreover, as the dust temperature increases, the soliton amplitude will increase.     

Modulational instability of a weakly relativistic ion acoustic wave in a warm plasma with nonthermal electrons

An investigation has been made of modulational instability of a nonlinear ion acoustic wave in a weakly relativistic warm unmagnetized nonthermal plasma whose constituents are an inertial ion fluid and nonthermally distributed electrons. Up to the second order of the perturbation theory, a nonlinear Schr?dinger type (NST) equation for the complex amplitude of the perturbed ion density is obtained. The coefficients of this equation show that the relativistic effect, the finite ion temperature and the nonthermal electrons modify the condition of the modulational stability. The association between the small-wavenumber limit of the NST equation and the oscillatory solution of the Korteweg－de Varies equation, obtained by a reductive perturbation theory, is satisfied.     

Modulational instability of a weakly relativistic ion acoustic wave in a warm plasma with nonthermal electrons

An investigation has been made of modulational instability of a nonlinear ion acoustic wave in a weakly relativistic warm unmagnetized nonthermal plasma whose constituents axe an inertial ion fluid and nonthermally distributed electrons. Up to the second order of the perturbation theory, a nonlinear Schr~dinger type (NST) equation for the complex amplitude of the perturbed ion density is obtained. The coefficients of this equation show that the relativistic effect, the finite ion temperature and the nonthermal electrons modify the condition of the modulational stability. The association between the small-wavenumber limit of the NST equation and the oscillatory solution of the Korteweg-de Varies equation, obtained by a reductive perturbation theory, is satisfied.     

Dynamical behaviour of non-linear quantum ion acoustic wave in weakly magnetized electron–positron–ion plasma

In order to investigate the propagation characteristics of linear and non-linear ion acoustic waves (IAWs) in electron–positron–ion quantum plasma in the presence of external weak magnetic field, we have used a quantum hydrodynamic model, and degenerate statistics for the electrons and positrons are taken into account. It is found that the linear dispersion relation of the IAW was modified by the externally applied magnetic field. By using the reductive perturbation technique, a gyration-modified Korteweg-de Vries equation is derived for finite amplitude non-linear IAWs. Time-dependent numerical simulation shows the formation of an oscillating tail in front of the ion acoustic solitons in the presence of a weak magnetic field. It is also seen that the amplitude and width of solitons and oscillating tails are affected by the relevant plasma parameters such as quantum diffraction, positron concentration, and magnetic field. We have performed our analysis by extending it to account for approximate soliton solution by asymptotic perturbation technique and non-linear analysis via a dynamical system approach. The analytical results show the distortion of the shape of the localized soliton with time, and the non-linear analysis confirms the generation of oscillating tails.     

Bifurcation analysis of nonlinear and supernonlinear dust–acoustic waves in a dusty plasma using the generalized (r,q) distribution function for ions and electrons

Bifurcation analysis of dust acoustic (DA) periodic waves in three components, unmagnetized dusty plasma system is investigated using the generalized (r, q) distribution function for ions and electrons. Depending on the different parameters of the system considered, all possible phase portraits, including periodic, homoclinic, superperiodic, and superhomoclinic trajectories, are presented. The existence of rarefactive and compressive solitary waves is proved. Also, the plasma system under consideration supports both nonlinear and supernonlinear DA periodic waves. It has been found that the double spectral indices r and q play a decisive effect on the bifurcation of the waves.     

Upstream ion wave excitation in an ion-beam–plasma system

Plasma normal modes in ion-beam–plasma systems were experimentally investigated previously only for the waves propagating in the downstream(along the beam) direction. In this paper, the ion wave excitation and propagation in the upstream(against the beam) direction in an ion-beam–plasma system were experimentally studied in a double plasma device. The waves were launched by applying a ramp voltage to a negatively biased excitation grid. Two kinds of wave signals were detected, one is a particle signal composed of burst ions and the other is an ion-acoustic signal arising from the background plasma. These signals were identified by the dependence of the signal velocities on the characteristics of the ramp voltage. The velocity of the burst ion signal increases with the decrease of the rise time and the increase of the peak-to-peak amplitude of the applied ramp voltage while that of the ion-acoustic signal is independent of these parameters.By adjusting these parameters such that the burst ion velocity approaches to the ion-acoustic velocity, the wave–particle interaction can be observed.     

Modulational instability of ion—acoustic waves in a warm plasma

Using the standard reductive perturbation technique,a nonlinear Schroedinger equation is derived to study the modulational instability of finite-amplitude ion-acoustic waves in a non-magnetized warm plasma.It is found that the inclusion of ion temperature in the equation modifies the nature of the ion-acoustic wave stability and the soliton stuctures.The effects of ion plasma temperature on the modulational stability and ion-acoustic wave properties are inestigated in detail.     

Effect of Bohm quantum potential in the propagation of ion–acoustic waves in degenerate plasmas

A theoretical investigation has been carried out on the propagation of the ion–acoustic(IA) waves in a relativistic degenerate plasma containing relativistic degenerate electron and positron fluids in the presence of inertial non-relativistic light ion fluid. The Korteweg-de Vries(K-dV), modified K-dV(m K-dV), and mixed m K-dV(mm K-dV) equations are derived by adopting the reductive perturbation method. In order to analyze the basic features(phase speed, amplitude, width,etc.) of the IA solitary waves(SWs), the SWs solutions of the K-dV, m K-dV, and mm K-d V are numerically analyzed. It is found that the degenerate pressure, inclusion of the new phenomena like the Fermi temperatures and quantum mechanical effects(arising due to the quantum diffraction) of both electrons and positrons, number densities, etc., of the plasma species remarkably change the basic characteristics of the IA SWs which are found to be formed either with positive or negative potential. The implication of our results in explaining different nonlinear phenomena in astrophysical compact objects, e.g.,white dwarfs, neutron stars, etc., and laboratory plasmas like intense laser–solid matter interaction experiments, etc., are mentioned.     

Attenuation characteristics of obliquely incident electromagnetic wave in weakly ionized dusty plasma based on modified Bhatnagar–Gross–Krook collision model

The attenuation characteristics of obliquely incident electromagnetic(EM) wave in L-Ka frequency band in weakly ionized dusty plasma are analyzed based on the modified Bhatnagar-Gross-Krook(BGK) collision model.According to the kinetic equation and the charging theory,the total complex dielectric constant of the weakly ionized dusty plasma is derived by considering that the minimum velocity of the electron accessible to the dust particle surface is non-zero and the second potential part of the collision cross-section contributes to the charging.The attenuation characteristics within the modified model are compared with those within the traditional model.The influence of the dusty plasma parameters and the incident angle of EM waves on the attenuation in weakly ionized dusty plasma is further analyzed.Finally,the influence of different reentry heights on the attenuation characteristics of the obliquely incident EM wave is discussed.The results show that the effect of the minimum electron velocity and the second term of the collision cross-section on the attenuation characteristics of EM waves cannot be ignored.When the dust density and dust radius are changed,the trends of the attenuation of obliquely incident EM waves are consistent,but the influence of dust density is weaker than that of dust radius due to the constraint of orbit-limited motion(OLM) theory.The plasma thickness,electron density,and incident angle are proportional to the attenuation amplitude of EM waves.The effect of different reentry heights on the attenuation obliquely incident EM waves is related to the electron density and plasma thickness.     

Calculation of ion energy distributions of argon excimer ions generated in helicon plasma

A program is developed to calculate the ion energy distributions （IEDs） of Ar2^＋ making use of a simplified kinetic model with a combination of Monte Carlo method. Several coefficients are used to realize good match between the calculated and measured results. Some important assumptions are confirmed： argon excimer ions have short lifetime, hence they are formed in a short range before the collecting electrode. The excimer ions that encounter collisions will be discarded because they turn to other ion species after they collide with argon atoms. From the calculated results some plasma parameters such as the cross section or neutral density in discharge could be evaluated.     

Physical aspects of dust–plasma interactions

Low-pressure gas discharge plasmas are known to be strongly affected by the presence of small dust particles. This issue plays a role in the investigations of dust particle-forming plasmas, where the dust-induced instabilities may affect the properties of synthesized dust particles. Also, gas discharges with large amounts of microparticles are used in microgravity experiments, where strongly coupled subsystems of charged microparticles represent particle-resolved models of liquids and solids. In this field, deep understanding of dust–plasma interactions is required to construct the discharge configurations which would be able to model the desired generic condensed matter physics as well as, in the interpretation of experiments, to distinguish the plasma phenomena from the generic condensed matter physics phenomena. In this review, we address only physical aspects of dust–plasma interactions, that is, we always imply constant chemical composition of the plasma as well as constant size of the dust particles. We also restrict the review to two discharge types: dc discharge and capacitively coupled rf discharge. We describe the experimental methods used in the investigations of dust–plasma interactions and show the approaches to numerical modelling of the gas discharge plasmas with large amounts of dust. Starting from the basic physical principles governing the dust–plasma interactions, we discuss the state-of-the-art understanding of such complicated, discharge-type-specific phenomena as dust-induced stratification and transverse instability in a dc discharge or void formation and heartbeat instability in an rf discharge.     

Influence of acoustic leakage at fluid–solid interface on interferometric detection of surface acoustic wave

When using laser interferometer to detect surface acoustic wave at fluid–solid interface, there are two factors which will cause the optical path length variation of the probe laser beam: interface deformation, and refractive index changes in fluid induced by acoustic leakage. Influence of acoustic leakage on laser interferometric detection for surface acoustic wave is researched here. A metal plate immersed in an infinite fluid is used as a physical model. Interface deformation due to laser-induced acoustic wave and pressure in fluid due to acoustic leakage are computed for select cases by finite element method. The optical path length variation caused by the two factors are calculated respectively and compared. The results show that the influence of acoustic leakage increases with the increasing acoustic impedance matching of fluid and solid, the peak-to-peak of influence degree increases linearly with the increasing acoustic impedance of fluid, and that decreasing the distance between the interferometer and interface can effectively reduce the influence of acoustic leakage.     

Shocks in an electronegative plasma with Boltzmann negative ions and κ-distributed trapped electrons

We derived a Schamel-Burgers equation to study the dynamics of nonlinear structures in dissipative electronegative plasma having Boltzmann negative ions and κ-distributed trapped electrons. A recently introduced Tangent hyperbolic method has been employed to get the solutions of the differential equations which contain fractional nonlinearity. The effects of different physical parameters particularly, the kinematic viscosity, the superthermality, the trapping efficiency and the electronegativity factor on the ion acoustic (IA) shock profiles have been elaborated. In case of non-dissipative electronegative plasma, the small amplitude double layers (DLs) have also been investigated. It has been elaborated that the DLs strongly depend on the system parameters. The results illustrate that the superthermality index and trapping parameter play disruptive role in the formation of DLs. Likewise, the electronegativity factor plays a dominant role in the shaping of the compressive DLs. The study can be supportive to understand the behavior of nonlinear structures as observed in the nature and laboratory plasmas.     

Phase change and stress wave in picosecond laser–material interaction with shock wave formation

When background gas is present in pulsed laser–material interaction, a shock wave down to the nanoscale will emerge. The background gas will affect the phase change and explosion in the target. This study is focused on the void dynamics and stress wave in a model material (argon crystal) under picosecond pulsed laser irradiation. Our results show that existence of ambient gas and the shock wave significantly suppresses the void formation and their lifetime. Void dynamics, including their growing rate, lifetime, and size under the influence of ambient gas are studied in detail. All the voids undergo an accelerating and decelerating process in the growth. The collapsing process is almost symmetrical to the growing process. Higher laser fluence is found to induce an obvious foamy structure. Stress wave formation and propagation, temperature contour, and target and gas atom number densities are studied to reveal the underlying physical processes. Although the interaction of the plume with ambient gas significantly suppresses the void formation and phase explosion, no obvious effect is found on the stress wave within the target. Very interestingly, secondary stress waves resulting from re-deposition of ablated atoms and void collapse are observed, although their magnitude is much smaller than the directly laser-induced stress wave.     

Positive ion speed at the plasma–sheath boundary of a negative ion-emitting electrode

One-dimensional fluid model for a planar sheath in front of a negative ion-emitting electrode surface immersed in a collision-less, non-magnetized, electronegative plasma is presented. It was found that the positive ion speed at the plasma–sheath boundary (PSB) increases linearly with negative ion emission from the electrode but attains a saturation value as soon as a virtual cathode is formed near the electrode surface. The effect of negative ion emission on the pre-sheath region shows that the potential drop increases across the pre-sheath in accordance with the rise in positive ion speed at the PSB. The sheath width obtained using the present model shows a similar trend as the Child-Langmuir law, but its magnitude is found to be consistently higher compared with a non-emitting electrode. A plausible explanation has been given to explain these effects.     

Spherical Kadomtsev–Petviashvili equation for dust acoustic waves with dust size distribution and two-charges-ions

The nonlinear dust acoustic waves in dusty plasmas with negative as well as positive ions and the combined effects of bounded spherical geometry and the transverse perturbation and the size distribution of dust grains are studied. Using the perturbation method, a spherical Kadomtsev–Petviashvili (SKP) equation that describes the dust acoustic waves is deduced.