Ion-acoustic Solitary Waves In Plasma Research Articles

Electron beam driven ion-acoustic solitary waves in plasmas with two kappa-distributed electrons

Formation and the basic features of arbitrary amplitude ion-acoustic solitary waves (IASWs) in a plasma consisting of warm positive ions, two kappa-distributed electrons and an electron beam are investigated by using the Sagdeev pseudopotential approach. It is shown that the soliton existence domain (Mach number limits) sensitively depends on temperature of ions, spectral index of cool electrons and concentration of hot electron species while spectral index of hot electrons, hot-to-cool electron temperature ratio and also concentration of electron beam do not considerably affect this domain. It is also found that temperature of electron beam only affect the existence domain of rarefactive solitons. Furthermore, it is shown that considered plasma medium supports the coexistence of positive and negative IASWs. Moreover, effect of different plasma parameters such as hot-to-cool electron density ratio, ion-to-cool electron temperature ratio, beam-to-ion density ratio, hot-to-cool electron temperature ratio and superthermality index of electron species on the basic features of positive and negative IASWs is investigated numerically. Finally, the effect of plasma parameters on the parametric regime of coexistence of compressive and rarefactive IASWs is studied and, for example, effect of temperature of positive ions and number density of hot electrons on polarity of IASWs is numerically investigated.

Studies on Ion-Acoustic Solitary Waves in Plasmas with Positrons and Two-Temperature Superthermal Electrons through Damped Zakharsov–Kuznetsov–Burgers Equation

Studies on Ion-Acoustic Solitary Waves in Plasmas with Positrons and Two-Temperature Superthermal Electrons through Damped Zakharsov–Kuznetsov–Burgers Equation

Classification of head-on collisions of ion-acoustic solitary waves in a plasma consisting of cold ions and Boltzmann electrons

Head-on collisions of ion-acoustic solitary waves in a collisionless plasma consisting of cold ions and Boltzmann electrons are studied using the particle-in-cell simulation. It is shown that the collision of solitary waves can occur under different scenarios. Solitary waves preserve or do not preserve their amplitudes and shapes after a collision, depending on their initial amplitudes. The range of initial amplitudes, at which a solitary wave preserves its identity after collisions, is established. The use of a diagram of initial amplitudes of colliding solitary waves to consider possible collision scenarios is discussed. The characteristic regions in the diagram of the initial amplitudes corresponding to different collision scenarios are determined, and a classification of head-on collisions of ion-acoustic solitary waves in a plasma is proposed.

Role of ion thermal velocity in the formation and dynamics of electrostatic solitary waves in plasmas

We perform fluid simulations to examine the effect of ion thermal velocity on the formation and dynamics of solitary waves in an unmagnetized two-component plasma consisting of ions and electrons. Based on the linear and nonlinear fluid theories, some of the previous studies have reported that the plasma with the electron temperature greater than the ion temperature (i.e., Te > Ti) supports ion acoustic solitary waves (IASWs), whereas the plasma with Te ≪ Ti supports electron acoustic waves (EASWs). In this paper, we have considered a wide range of ion temperatures (with fixed electron temperature) to examine the criteria of temperature and thermal velocities in the generation of EASWs and IASWs in plasmas. Our simulation shows that the plasma with Ti > Te possesses two wave modes depending on the ratio of its thermal velocities. When the ratio of electron to ion thermal velocities R = Vthe/Vthi > 1, the system supports the generation of IASWs, whereas for R < 1, it supports the generation of EASWs. The analysis of characteristics like the amplitude, width, and phase speed of these solitary waves implies that the EASWs have a negative potential, whereas the IASWs have the positive potential. The transition from IASWs to EASWs occurs when the phase speed of the solitary wave exceeds the limiting value of 3Vthe. This simulation study presents the detailed investigation of the evolution of EASWs and IASWs generated in plasmas having Ti > Te, which will have implications in modeling such waves in space and laboratory plasmas.

Acceleration and Trapping of Ions upon Collision of Ion-Acoustic Solitary Waves in Plasma with Negative Ions

The phenomena occurring under head-on collision of ion-acoustic solitary waves in collisionless plasma consisting of positive and negative ions and electrons obeying the Boltzmann distribution are considered. Using particle-in-cell simulations, it is shown that large-amplitude compressive ion-acoustic solitary waves do not preserve their identity after the collision. Their amplitudes decrease and their shapes change. It is shown that the collision is accompanied by the generation of fast positive ions the velocity of which can exceed more than threefold the speed of sound. In addition, the collision is accompanied by the trapping of negative ions by the field of ion-acoustic solitary waves formed after the collision.

Collision of Ion-Acoustic Solitary Waves in Plasma

The process of collision of ion-acoustic solitary waves in a collisionless plasma with cold ions and Boltzmann electrons is studied using numerical simulations. It is shown that solitary waves with sufficiently large amplitudes do not preserve their identity after the collision. Their amplitudes decrease, and the shapes change. It is found that the collision is accompanied by the generation of fast ions with velocities exceeding threefold the ion sound speed.

Particle trapping and ponderomotive processes during breaking of ion acoustic waves in plasmas

Recent fluid simulations show that the ponderomotive potentials and ponderomotive frequencies of electrons and ions can be used as proxies to identify steepening and breaking of the ion acoustic solitary waves (IASWs) in plasmas. However, the behavior of these proxies may deviate in the presence of kinetic effects such as particle trapping. We performed one-dimensional particle-in-cell (PIC) simulations to examine the effects of kinetic processes on the behavior of these proxies at the breaking of IASWs in plasmas. The electron and ion equilibrium densities were superimposed by a long-wavelength Gaussian type perturbation, which initially evolves into two IASWs observed as two phase space vortices due to the trapping of electrons in the ion acoustic (IA) potentials. These IASW structures grow due to the steepening of their trailing edges, and later they break into a chain of IA phase space vortices. Each of these vortices is associated with a bipolar electric field resulting in a positive potential structure. We examined the amplitude, width, and phase velocity of the IASWs at their breaking process to clarify their link with the trapping velocity. In addition, we estimated electron and ion ponderomotive potentials and frequencies from the PIC simulations to verify their applicability in identifying wave breaking limit under the kinetic regime. The present study shows that the behavior of the ponderomotive potential during the IA wave breaking process is similar to the one, which is proposed through fluid simulations. We find that IA wave breaking occurs when the maximum trapping velocity of the electron (Vtrap + Vs) exceeds its thermal velocity. The present simulation study shows that both maximum electron trapping velocity and ponderomotive potential can be used to identify the IA wave breaking processes in plasmas.

Arbitrary amplitude ion-acoustic solitary waves in a two-temperature nonextensive electron plasma

Effects of presence of ions on the existence and structure of arbitrary amplitude ion-acoustic solitary waves in a plasma consisting of thermal ions and two-temperature nonextensive electrons are investigated. It is shown that solitons of both polarity (compressive and rarefactive) can exist in such a plasma, depending on the range of the plasma parameters. Also, it is seen that the maximum amplitude and the width of both soliton types depend sensitively on the temperature and concentration of ions. To better understand the role of positive ions, the presented model is reduced to a Maxwellian plasma and the results are compared to their Maxwellian counterparts.

W-type ion-acoustic solitary waves in plasma consisting of cold ions and nonthermal electrons

Sagdeev potential approach is used for the study of nonlinear propagation of ion-acoustic waves in plasma consisting of cold positive ions and nonthermal electrons. The nonlinear equation so derived are analysed with the help of Bogoliubov–Mitropolosky method. The profiles of Sagdeev potential solitary waves are evaluated in first-, second- and third- order which are depicted for different values of nonthermal parameter of electrons. It is seen that nonthermal electrons has considerable impact on the shape of ion-acoustic solitary waves in each order. The plasma consisting of cold positive ions and no negative ions can support the formation of compressive as well as W-type solitary waves in second- and third- order for certain value of nonthermal parameter of electrons. The results are new because W-type ion-acoustic solitary wave is found by earlier authors in plasma in presence of negative ions only. The ion-acoustic solitary waves near critical value of nonthermal parameter and arbitrary amplitude solitary waves in presence of nonthermal electrons have also been studied in the paper. Moreover, the solution for ion-acoustic double layers in plasma consisting of nonthermal electrons is obtained. Our results in the paper would be useful to understand the nonlinear wave processes in ionospheric and magnetospheric multicomponent plasma having nonthermal electrons.

Application of Particle-in-Cell Simulation to the Description of Ion Acoustic Solitary Waves

1-D particle-in-cell simulations are used to investigate the propagation and decomposition of the ion acoustic solitary waves (IASWs) in plasmas. Our results show that for small-amplitude conditions, IASWs are stable and the simulation results are consistent with the theoretical predictions of the reductive perturbation method. As the amplitudes of IASWs increase, the waves become unstable and trains of oscillating waves are emitted behind the main waves. When the amplitude is large enough, the wave cannot exist and will decay into a series of waves with a small amplitude. By comparing our simulations with the theoretical solutions of Kortewag–de Vries soliton, the upper limitation of the amplitude of IASWs in plasmas is found. Moreover, our results show that although the reductive perturbation method is valid only for small perturbations, the application scope of the reductive perturbation method can be expanded to describe the potential profiles of IASWs with any amplitude. Meanwhile, the application scope for the density profiles is still limited in the perturbation cases.

Head-on collision of two ion-acoustic solitary waves in plasmas with electrons described by Tsallis distribution

The problem of the head-on collision of two ion-acoustic solitary waves (IASWs) is addressed in electronegative plasmas with a nonextensive electron velocity distribution. Our plasma model is inspired from the experimental studies of Ichiki et al. (2001). Using the extended Poincare–Lighthill–Kuo (PLK) perturbation method, the phase shifts of the head-on collision are obtained. Analytical and numerical results reveal that the magnitude of the phase shift of the IASWs depends sensitively on the number density ratios μ and υ, the mass ratio σ as well as the nonextensive parameter q. For a given mass ratio σ≃0.27 (Ar+−SF6−), the magnitude of the phase shift increases with an increase of the nonextensive parameter q. An increase of the electron-to-positive ion density ratio μ lowers the phase shift, a trend which is much perceptible for q>1. As σ increases [σ≃0.89 (Xe+−SF6−)], the phase shift becomes larger.

Modified ion-acoustic solitary waves in plasmas with field-aligned shear flows

The nonlinear dynamics of ion-acoustic waves is investigated in a plasma having field-aligned shear flow. A Koeteweg-deVries-type nonlinear equation for a modified ion-acoustic wave is obtained which admits a single pulse soliton solution. The theoretical result has been applied to solar wind plasma at 1 AU for illustration.

Ion-acoustic Solitary Waves in a q-Nonextensive Plasma1,2

Based on the three-dimensional nonextensive distribution function and hydrodynamic equations, the effects of nonextentive electron distribution on the structure and property of ion-acoustic solitary waves in plasmas have been studied. By theoretical analysis, an equation involving the Sagdeev-type pseudo-potential is derived, which is used to study the amplitude and width of ion-acoustic solitary waves, as well as the spatial distribution of electron number density, for different values of the nonextension parameter q. The numerical results suggest that the allowable domain where the ion-acoustic solitary wavesmay exist is determined by q, and that both the spatial profile of ion-acoustic waves and the electron density distribution are significantly affected by the nonextensive effect of electrons.

Numerical simulation of the ion-acoustic solitary waves in plasma based on lattice Boltzmann method

In this paper, a new lattice Boltzmann model for the ion-acoustic solitary waves in plasma is proposed. By using the Chapman–Enskog expansion and the multi-scale time expansion, a series of partial differential equations in different time scales are obtained. By selecting the appropriate moments of the equilibrium distribution functions, the macroscopic equations are recovered. In numerical examples, we simulate the propagation of the ion-acoustic solitary waves. Numerical results show that the lattice Boltzmann method is an effective tool for the study of the ion-acoustic solitary waves in plasma.

Non-planar ion-acoustic solitary waves and their head-on collision in a plasma with nonthermal electrons and warm adiabatic ions

By using the model of Cairns et al. [Geophys. Rev. Lett. 22, 2709 (1995)], the head-on collision of cylindrical/spherical ion-acoustic solitary waves in an unmagnetized non-planar plasma consisting of warm adiabatic ions and nonthermally distributed electrons is investigated. The extended Poincaré-Lighthill-Kuo perturbation method is used to derive the modified Korteweg-de Vries equations for ion-acoustic solitary waves in this plasma system. The effects of the plasma geometry m, the ion to electron temperature ratio σ, and the nonthermality of the electron distribution α on the interaction of the colliding solitary waves are studied. It is found that the plasma geometries have a big impact on the phase shifts of solitary waves. Also it is important to note that the phase shifts induced by the collision of compressive and rarefactive solitary waves are very different. We point out that this study is useful to the investigations about the observations of electrostatic solitary structures in astrophysical as well as in experimental plasmas with nonthermal energetic electrons.

The effects of nonthermality on the interaction of ion-acoustic solitary waves in a plasma consisting of warm adiabatic ions and nonthermal electrons

An investigation has been made on the head-on collision of two ion-acoustic solitary waves in an unmagnetized nonthermal plasma whose constituents are warm adiabatic ions and nonthermally distributed electrons. The extended Poincaré–Lighthill–Kuo perturbation method is used to derive the Korteweg–de Vries equations for both compressive and rarefactive ion-acoustic solitary waves in this plasma system. The effects of the ion to electron temperature ratio σ and the nonthermality of the electron distribution α on the interaction and structure of the colliding solitary waves are investigated. It is found that these factors, especially α, can significantly modify the properties of the waves and their collisions, and that the collisions for the two types of solitary waves are very different. It is also important to note that the phase shifts induced by the collision of compressive and rarefactive solitary waves are also different. The relevance of this investigation to the observations in astrophysical plasmas as well as experimental plasmas with nonthermally distributed electrons is briefly pointed out.

Ion-acoustic solitary waves in ion-beam plasma with Boltzmann electrons

Particle simulations and a pseudopotential method were used to study ion-acoustic solitary waves in a plasma composed of Boltzmann electrons and kinetic beam ions. Pseudopotential theory was first applied to determine how ion-acoustic solitary waves can exist in a two-component plasma. Then, particle simulations were carried out, wherein ion-acoustic solitary waves were excited by modulating the bias grid voltage in a double plasma model. For the modulation, the potential of the grid bias was rapidly decreased, such that hump-type ion-acoustic solitary waves with good Gaussian shape were excited one after another, forming a train of waves. The simulation also showed that the phase velocities of ions decrease sharply when the solitary wave occurs, which indicates that the solitary ion-acoustic wave is excited via the inverse Landau damping process.

Applications of a simplified bilinear method to ion-acoustic solitary waves in plasma

In this paper, we propose a computational method for nonlinear partial differential equations modeling ion-acoustic waves as well as dusty plasmas in laboratory and space sciences. Many types of solitary waves including soliton solutions, N-soliton solutions and singular N-soliton solutions are derived. The characteristic line method and graphical analysis are applied to discuss the solitonic propagation and collision, including the bidirectional solitons and elastic interactions. Furthermore, the effects of inhomogeneities of media and nonuniformities of boundaries, depicted by the variable coefficients, on the soliton behavior are discussed.

Electrostatic Korteweg-deVries solitary waves in a plasma with Kappa-distributed electrons

The Korteweg-deVries (KdV) equation that describes the evolution of nonlinear ion-acoustic solitary waves in plasmas with Kappa-distributed electrons is derived by using a reductive perturbation method in the small amplitude limit. We identified a dip-type (negative) electrostatic KdV solitary wave, in addition to the hump-type solution reported previously. The two types of solitary waves occupy different domains on the κ (Kappa index)-V (propagation velocity) plane, separated by a curve corresponding to singular solutions with infinite amplitudes. For a given Kappa value, the dip-type solitary wave propagates faster than the hump-type. It was also found that the hump-type solitary waves cannot propagate faster than V = 1.32.

Propagation and interaction of ion—acoustic solitary waves in a quantum electron—positron—ion plasma

This paper discusses the existence of ion-acoustic solitary waves and their interaction in a dense quantum electronpositron—ion plasma by using the quantum hydrodynamic equations. The extended Poincaré—Lighthill—Kuo perturbation method is used to derive the Korteweg-de Vries equations for quantum ion—acoustic solitary waves in this plasma. The effects of the ratio of positrons to ions unperturbation number density p and the quantum diffraction parameter He (Hp) on the newly formed wave during interaction, and the phase shift of the colliding solitary waves are studied. It is found that the interaction between two solitary waves fits linear superposition principle and these plasma parameters have significantly influence on the newly formed wave and phase shift of the colliding solitary waves. The investigations should be useful for understanding the propagation and interaction of ion-acoustic solitary waves in dense astrophysical plasmas (such as white dwarfs) as well as in intense laser-solid matter interaction experiments.