Solitary Waves In Plasma Research Articles

Effect of anisotropy of lighter and heavier ions on solitary waves in a multi-ion plasma

We have studied the combined effect of the pressure anisotropies of lighter and heavier ions of opposite polarities on solitary waves in a plasma composed of these ions as well as kappa described electrons of solar and cometary origin. Using the theory of Chew, Goldberger, and Low (the CGL theory), the anisotropies of all three ions have been included in the derivation of the Zakharov–Kuznetsov equation. The effects of various combinations of pressure anisotropies of both lighter as well as heavier ions of opposite polarities have been considered. From the figures, plotted for parameters observed at comet Halley, it is seen that different properties of the solitary wave such as width and amplitude, as well as dispersion and nonlinear coefficients, are profoundly affected by the anisotropies of the ions. Also, the pressure anisotropy of the lighter ions determines the polarity of the solitary waves: the plasma supports compressive (rarefactive) solitary waves when the lighter ions are pressure isotropic (anisotropic).

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.

A lattice Boltzmann model for the ion- and electron-acoustic solitary waves in beam-plasma system

In this paper, a lattice Boltzmann model for the ion- and electron-acoustic solitary waves in beam-plasma system 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- and electron-acoustic solitary waves. Numerical results show that the lattice Boltzmann method is an effective tool for the study of the ion- and electron-acoustic solitary waves in plasma.

Ion acoustic solitary waves in plasmas with nonextensive distributed electrons, positrons and relativistic thermal ions

The theoretical and numerical studies have been investigated on nonlinear propagation of weakly relativistic ion acoustic solitary waves in an unmagnetized plasma system consisting of nonextensive electrons, positrons and relativistic thermal ions. To study the characteristics of nonlinear propagation of the three-component plasma system, the reductive perturbation technique has been applied to derive the Korteweg–de Vries equation, which divulges the soliton-like solitary wave solution. The ansatz method is employed to carry out the integration of this equation. The effects of nonextensive electrons, positrons and relativistic thermal ions on phase velocity, amplitude and width of soliton and electrostatic nonlinear propagation of weakly relativistic ion acoustic solitary waves have been discussed taking different plasma parameters into consideration. The obtained results can be useful in understanding the features of small amplitude localized relativistic ion acoustic solitary waves in an unmagnetized three-component plasma system for hard thermal photon production with relativistic heavy ions collision in quark–gluon plasma as well as for astrophysical plasmas.

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.

Ion thermal effects on slow mode solitary waves in plasmas with two adiabatic ion species

Using both the Sagdeev and Korteweg-de Vries (KdV) methods, ion thermal effects on slow mode ion acoustic solitons and double layers are investigated in a plasma with two adiabatic positive ion species. It is found that reducing the gap between the two ion thermal speeds by increasing the relative temperature of the cool ions increases the typical soliton/double layer speeds for all values of the ion-ion density ratio and reduces the range in the density ratio that supports double layers. The effect of increasing the relative cool ion temperature on the soliton/double layer amplitudes depends on the relative densities. For lower values of the ion density ratio, an increase in cool ion temperature leads to a significant decrease in soliton/double layer amplitude, so one may find that solitons of all permissible speeds lie within the range of KdV theory.

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.

Solitary waves in a plasma with oppositely charged dust (heavier, pair ions) and kappa modeled lighter ions and electrons

We investigate the existence of compressive and rarefactive solitary waves in a five-component plasma. Positively and negatively multiply charged heavier ions (dust), kappa function described photo-electrons, hot electrons and ions form the five components. The pseudo-potential approach is used to determine the existence of a soliton. We find that the Sagdeev potential as well as the amplitude of the solitary wave for both compressive and rarefactive solitons increases with increasing spectral indices of the kappa distributions describing the cometary species. The magnitude of the amplitude of the solitary wave increases with increasing positively charged ion densities and charge numbers, but decreases with increasing charge numbers of the negative ions for both type of solitons.

Particle-in-cell simulation of the head-on collision between two ion acoustic solitary waves in plasmas

The head-on collision of two ion acoustic solitary waves in plasmas composed of hot electrons and cold ions has been studied by using the Poincare-Lighthill-Kuo (PLK) perturbation method and one-dimensional Particle-in-Cell (PIC) simulation. Then the phase lags of ion acoustic solitary waves (IASWs) obtained from the two approaches have been compared and discussed. It has been found that: if the amplitudes of both the colliding IASWs are small enough, the phase lags obtained from PLK method are in good agreement with those obtained from PIC simulation. As the amplitudes of IASWs increase, the phase lags from PIC simulation become smaller than the analytical ones from PLK method. Besides, the PIC simulation shows the phase lag of an IASW involved in collision depends not only on the characteristics of the wave it collides with but also on itself, which disagrees with the prediction of the PLK method. Finally, the application scopes of the PLK method in studying both the single IASW and the head-on collisions of IASWs have been studied and discussed, and the latter turns out to be more strict.

Dust ion acoustic (DIA) solitary waves in plasmas with weak relativistic effects in electrons and ions

In the new investigation of dust-ion acoustic (DIA) waves with negative dust charges and weakly relativistic ions and electrons in the plasma, compressive and rarefactive DIA solitons of interesting characters are established through the Korteweg-de Vries (KdV) equation. Eventually, the amplitudes of the compressive DIA solitons are found to be constant at some critical temperature ratio αc (electron to ion temperature ratio) identifying some critical dust charge Zdc. It is predicted, that the reception of dust charges by the plasma particles at the variation of temperature starts functioning to the growth of compressive soliton’s constant stage of amplitude after the state of critical αc. The identification of critical dust charge (Zdc) which is found to be very great for solitons of constant amplitudes becomes feasible for very small dust to ion density ratio (σ). But it can be achieved, we observe, due to the relativistic increase in ion-density as in mass, which is also a salient feature of this investigation.

On the existence and stability of electrostatic structures in non-Maxwellian electron-positron-ion plasmas

Electrostatic solitary waves in plasmas are the focus of many current studies of localized electrostatic disturbances in both laboratory and astrophysical plasmas. Here, an investigation of the nonlinear dynamics of plasma evolving in two dimensions, in the presence of excess superthermal background electrons and positrons, is undertaken. We investigate the effect of a magnetic field on weakly nonlinear ion acoustic waves. Deviation from the Maxwellian distribution is effectively modelled by the kappa model. A linear dispersion relation is derived, and a decrease in frequency and phase speed in both parallel and perpendicular modes can be seen, when the proportion of positrons to electrons increases. We show that ion acoustic solitary waves can be generated during the nonlinear evolution of a plasma fluid, and their nonlinear propagation is governed by a Zakharov-Kuznetsov (ZK) type equation. A multiple scales perturbation technique is used to derive the ZK equation. The solitary wave structures are dependent on the relation between the system parameters, specifically the superthermality of the system, the proportion of positron content, magnetic field strength, and the difference between electron and positron temperature. The parametric effect of these on electrostatic shock structures is investigated. In particular, we find that stronger superthermality leads to narrower excitations with smaller potential amplitudes. Increased positron concentration also suppresses both the amplitude and the width of solitary wave structures. However, the structures are only weakly affected by temperature differentials between electrons and positrons in our model.

Head-on collision of electron-acoustic solitary waves in a plasma with superthermal hot electrons

The head-on collision between two electron-acoustic solitary waves in an unmagnetized plasma is investigated, including a cold electron fluid, hot electrons obeying a superthermal distribution and stationary ions. By using extended Poincare′-Lighthill-Kuo perturbation method, the analytical phase shifts following head-on collision are derived. Effects of the ratio of number density of hot electrons to number density of cold electrons α and superthermal parameter k on phase shifts are studied. It is found that hot-to-cold electron density ratio significantly modifies the phase shifts.

Nonlinear dynamics of multidimensional electrostatic excitations in nonthermal plasmas

Electrostatic solitary waves in plasmas are the focus of many current studies of localized electrostatic disturbances in both laboratory and astrophysical plasmas. Motivated by recent experimental observations, in which electrostatic solitary structures were detected in laser-plasma experiments, we have undertaken an investigation of the nonlinear dynamics of plasma evolving in two dimensions, in the presence of excess superthermal background electrons. We investigate the effect of a magnetic field on weakly nonlinear ion-acoustic waves. Deviation from the Maxwellian distribution is effectively modelled by the kappa model. A linear dispersion relation is derived, and a decrease in frequency and phase speed in both parallel and perpendicular modes can be seen, which is due to excess superthermal electrons, and which is stronger in the upper mode, and hardly noticeable in the lower (acoustic) mode. We show that ion-acoustic solitary waves can be generated during the nonlinear evolution of a plasma fluid, and their nonlinear propagation is governed by a Zakharov–Kuznetsov (ZK) type equation. A multiple scales perturbation technique is used to derive the ZK equation. Shock excitations can be produced if we allow for dissipation in the model, resulting in a Zakharov–Kuznetsov Burgers type equation. Different types of shock solutions and solitary waves are obtained, depending on the relation between the system parameters, and the effect of these on electrostatic shock structures is investigated numerically. A parametric investigation is conducted into the role of plasma nonthermality and magnetic field strength.

Ion acoustic solitary waves in electron-positron-ion plasmas with q-nonextensive electrons and high relativistic ions

Propagation of small amplitude ion acoustic solitary waves in plasmas containing q-nonextensive electrons, thermal positrons and high relativistic ions is addressed in this paper. Our results show that the Korteweg-de Vries equation describes the nonlinear waves in such plasmas. The amplitude and the width of the solitons are derived and the effects of relativistic ions and q-nonextensive distribution of electrons on these quantities are discussed.

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.

Cylindrical and spherical ion acoustic solitary waves in electron-positron-ion plasmas with superthermal electrons

Propagation of cylindrical and spherical ion acoustic solitary waves in plasmas consisting of cold ions, superthermal electrons and thermal positrons are investigated. It is shown that cylindrical/spherical Korteweg-de-Vries equation governs the dynamics of ion-acoustic solitons. The effects of nonplanar geometry and also superthermal electrons on the characteristics of solitary wave structures are studied using numerical simulations. Obtained results are compared with the results of the other published papers and errors in the results of some papers are pointed.

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.

Spherical electron acoustic solitary waves in plasma with suprathermal electrons

A reductive perturbation technique is employed to solve the fluid-Poisson equations in spherical geometry describing a weakly nonlinear electron–acoustic (EA) waves in unmagnetized plasma consisting of stationary ions, cold electrons and kappa distributed hot electrons. It is shown that a variable coefficient Kadomtsev–Petviashvili (KP) equation governs the evolution of scalar potential describing propagation of EA waves. The influence of suprathermality and geometry effects on propagation of EA solitary waves is investigated. We found that when electrons evolve toward their thermodynamic equilibrium, EA solitons are generated with large amplitudes. Also it is shown that EA solitary structures can be significantly modified by transverse perturbations.