Formation Of Solitary Structures Research Articles

Nonlinear ion-acoustic waves in e–p–i plasmas with (r, q) distributed electrons and positrons

The influence of the low energy part of the velocity distribution on the propagation characteristics of the nonlinear ion-acoustic waves is investigated in this study by employing the double spectral index (r, q) distribution function. We present an ample study to ascertain how the formation of compressive and rarefactive ion-acoustic solitary structures is influenced by the low energy particles in the distribution profile. We found that only compressive structures are formed for flat top distribution; however, both compressive and rarefactive structures are admissible for spiky distribution. The effect of spectral indices r and q on the formation of solitary structures is explored in detail, and a brief comparison with the Maxwellian and kappa distribution is also given. The present study is imperative in understanding the role of flat top or spiky distributions in plasmas, where positrons are present, and simultaneous observations of such distributions.

Formation of solitary structures and envelope solitons in electron acoustic wave in inner magnetosphere plasma with suprathermal ions

AbstractThe propagation of electron acoustic solitary waves is investigated in magnetized two‐temperature electron plasma with supra‐thermal ion. By using the reductive perturbation technique, the Korteweg de‐Vries (KdV) equation is derived. Later solving this equation, a solitary wave solution has been derived. These are mainly in astrophysical plasmas where changes of local charge density, temperature, and energy of particles produce considerable effects on the plasma system. The effects of supra‐thermality, density, and Mach number on solitary structures are studied in detail. The results show that the supra‐thermal index (κ) and ion to electron temperature ratio (σ) alters the regime where solitary waves may exist. While studying the solitary profile for different parametric variation some interesting conclusion can be drawn; it is shown that the solitary profile becomes flatter. This can be due to the thermal energy associated with the hot electrons. However, with the increase in ion density with respect to the cold electrons' density, the solitary waves become steeper and sharper. This is due to the comparatively heavier mass of ions. The density of cold electron also increases the solitary structures in a similar manner. The higher the density of cold electrons, sharper will be the profile. The above findings will be helpful in understanding many astrophysical phenomena and data obtained by space missions. For a further study, we keep the investigation of the formation of other kinds of stationary structures like shocks, double layers, etc.

Formation of Solitary Structures and Double Layer in Weakly Degenerate Electron-Ion Quantum Plasma in Ionosphere

In this paper, we consider ionospheric plasma consisting of weakly degenerate electrons and heavy ions. We embrace our hydrodynamic model by including the quantum diffraction term. By employing Sagdeev's pseudo-potential method, we obtain double layers and soliton structure. We have studied the various parametric dependence of solitary structures and double layers. The results thus obtained might be helpful in the studies of many high energy astrophysical phenomena.

Shock waves and the formation of solitary structures in electron acoustic wave in inner magnetosphere plasma with relativistically degenerate particles

The inner magnetosphere of Earth houses relativistically degenerate particles in which the formation of shocks and solitons occurs. In this paper we have considered plasma containing relativistically degenerate warm electrons and cold inertial electrons which give rise to electron acoustic solitary structure. We have also considered collisions which amount to dissipation actions and shocks. A KdV Burger equation has been derived by standard reductive perturbation technique and numerically analyzed by employing the celebrated Tan-hyperbolic method. The results are important in explaining the observed geo-magnetic storm in recent years.

Electrostatic wave instability and soliton formation with non-thermal electrons in O-H plasma of ionosphere

It is pointed out that the presence of non-thermal electrons and protons in oxygen plasma of the ionosphere plays a destructive role in the formation of electrostatic structures by nonlinear ion acoustic waves (IAWs). On the other hand, linear electrostatic perturbations at different IAW frequencies are excited by the field-aligned shear flow in oxygen-hydrogen plasma of the upper ionosphere, and non-thermal electrons cause an increase in the growth rate. The excitation of IAW and formation of solitary structures in the ionosphere are investigated at altitudes of 600 km and 1000 km in the auroral region.

Obliquely propagating ion acoustic solitary structures in the presence of quantized magnetic field

The effect of linear and nonlinear propagation of electrostatic waves have been studied in degenerate magnetoplasma taking into account the effect of electron trapping and finite temperature with quantizing magnetic field. The formation of solitary structures has been investigated by employing the small amplitude approximation both for fully and partially degenerate quantum plasma. It is observed that the inclusion of quantizing magnetic field significantly affects the propagation characteristics of the solitary wave. Importantly, the Zakharov-Kuznetsov equation under consideration has been found to allow the formation of compressive solitary structures only. The present investigation may be beneficial to understand the propagation of nonlinear electrostatic structures in dense astrophysical environments such as those found in white dwarfs.

Nonlinear coupling of kinetic Alfven waves with acoustic waves in a self-gravitating dusty plasma with adiabatic trapping

In this paper, linear and nonlinear coupling of kinetic Alfven and acoustic waves has been studied in a dusty plasma in the presence of trapping and self-gravitation effects. In this regard, we have derived the linear dispersion relations for positively and negatively coupled dust kinetic Alfven-acoustic waves. Stability analysis of the coupled dust kinetic Alfven-acoustic wave has also been presented. The formation of solitary structures has been investigated following the Sagdeev potential approach by using the two-potential theory. Numerical results show that the solitary structures can be obtained only for sub-Alfvenic regimes in the scenario of space plasmas.

Nonlinear density excitations in electron-positron-ion plasmas with trapping in a quantizing magnetic field

In the present work, we have investigated the effect of trapping as a microscopic phenomenon on the formation of solitary structures in the presence of a quantizing magnetic field in an electron-positron-ion (e-p-i) plasma having degenerate electrons and positrons, whereas ions are taken to be classical and cold. We have found that positron concentration, quantizing magnetic field, and finite electron temperature effects not only affect the linear dispersion characteristics of the electrostatic waves under consideration but also have a significant bearing on the propagation of solitary structures in the nonlinear regime. Importantly, the system under consideration has been found to allow the formation of compressive solitary structures only. The work presented here may be beneficial to understand the propagation of nonlinear electrostatic structures in dense astrophysical environments and in intense-laser plasma interactions.

Properties of solitary ion acoustic waves in a quantized degenerate magnetoplasma with trapped electrons

We have undertaken the investigation of ion acoustic solitary waves in both weakly and strongly quantized degenerate magnetoplasmas. It is seen that a singular point clearly demarcates the regions of weak and strong quantization due to the ambient magnetic field. The effect of the magnetic field is taken into account via the parameter η0=ℏωce/εFe and the Mach number, and their effect on the formation of solitary structures is investigated in both cases and some results are presented graphically.

Finite amplitude solitary structures of coupled kinetic Alfven-acoustic waves in dense plasmas

In this paper, we have investigated the nonlinear propagating coupled Kinetic Alfven-acoustic waves in a low beta degenerate quantum plasma in the presence of trapped Fermi electrons using the quantum hydrodynamic (QHD) model. By using the two potential theory and the Sagdeev potential approach, we have investigated the formation of solitary structures for coupled kinetic Alfven-acoustic waves in the presence of quantum mechanically trapped electrons. We have shown that there are regions of propagation and non-propagation for such solitary structures. We have also highlighted the differences between the classical and quantum mechanically trapped electrons. Interestingly, it has been found that the nature of the nonlinearity for the quantum mechanically trapped electrons is different from its classical counterpart. The results presented here may have applications in white dwarf asteroseismology as well as next generation laser-plasma experiments where low beta plasma condition is met.

Obliquely propagating quasi one dimensional electrostatic solitary structures in dense magnetoplasmas with trapped electrons

In the present investigation, we have studied the linear and nonlinear propagation of electrostatic waves in a dense magnetoplasma with trapped electrons. Using the small amplitude approximation, formation of solitary structures has been studied both for fully and partially degenerate plasmas. The theoretical results obtained have been analyzed numerically for the parameters typically found in white dwarfs. The present work may be beneficial to understand the propagation of solitary structures with weak transverse perturbation with special reference to white dwarf asteroseismology.

Formation of solitary structures in uniform and nonuniform magnetoplasmas with superthermal electrons: a non-reductive perturbative approach

Electrostatic solitary structures are studied in uniform and nonuniform magnetoplasmas with superthermal electrons. In the linear analysis, the differences in the acoustic frequencies for Maxwellian, Cairns, and Kappa distributed electrons for both homogeneous and inhomogeneous plasmas are highlighted and discussed. It is shown that using the linear dispersion relation, nonlinear Zakharov-Kuznetsov (ZK) equation can be derived both for the homogeneous and inhomogeneous magnetoplasmas. The solution of the ZK equation is presented using the tangent hyperbolic method. It is found that the increasing magnetic field and the angle of propagation enhances the amplitude whereas the increasing number density mitigates the amplitude of the acoustic drift solitary wave. Furthermore, it is observed that the amplitude of the solitary structure is maximum for Cairns, intermediate for Maxwellian, and minimum for the Kappa distributed electrons. The results presented in this paper may be beneficial to understand the formation of electrostatic drift solitary waves in planetary environments where the nonthermal population of electrons are observed by various satellite missions.

Effect of trapping in a degenerate plasma in the presence of a quantizing magnetic field

Effect of trapping as a microscopic phenomenon in a degenerate plasma is investigated in the presence of a quantizing magnetic field. The plasma comprises degenerate electrons and non-degenerate ions. The presence of the quantizing magnetic field is discussed briefly and the effect of trapping is investigated by using the Fermi-Dirac distribution function. The linear dispersion relation for ion acoustic wave is derived in the presence of the quantizing magnetic field and its influence on the propagation characteristics of the linear ion acoustic wave is discussed. Subsequently, fully nonlinear equations for ion acoustic waves are used to obtain the Sagdeev potential and the investigation of solitary structures. The formation of solitary structures is studied both for fully and partially degenerate plasmas in the presence of a quantizing magnetic field. Both compressive and rarefactive solitons are obtained for different conditions of temperature and magnetic field.

Vlasov simulation of electrostatic solitary structures in multi‐component plasmas

Electrostatic solitary structures have been observed in the Earth's magnetosheath by the Cluster spacecraft. Recent theoretical work has suggested that these solitary structures are modeled by electron acoustic solitary waves existing in a four‐component plasma system consisting of core electrons, two counter‐streaming electron beams, and one species of background ions. In this paper, the excitation of electron acoustic waves and the formation of solitary structures are studied by means of a one‐dimensional electrostatic Vlasov simulation. The present result first shows that either electron acoustic solitary waves with negative potential or electron phase‐space holes with positive potential are excited in four‐component plasma systems. However, these electrostatic solitary structures have longer duration times and higher wave amplitudes than the solitary structures observed in the magnetosheath. The result indicates that a high‐speed and small free energy source may be needed as a fifth component. An additional simulation of a five‐component plasma consisting of a stable four‐component plasma and a weak electron beam shows the generation of small and fast electron phase‐space holes by the bump‐on‐tail instability. The physical properties of the small and fast electron phase‐space holes are very similar to those obtained by the previous theoretical analysis. The amplitude and duration time of solitary structures in the simulation are also in agreement with the Cluster observation.

Effects of trapping and finite temperature in a relativistic degenerate plasma

In the present work, we have undertaken, for the first time, investigation on the effect of trapping on the formation of solitary structures in relativistic degenerate plasmas. Such plasmas have been observed in dense astrophysical objects, and in laboratory these may result due to the interaction of intense lasers with matter. We have used the relativistic Fermi-Dirac distribution to describe the dynamics of the degenerate trapped electrons by solving the kinetic equation. The Sagdeev potential approach has been employed to obtain the arbitrary amplitude solitary structures both when the plasma has been considered cold and when small temperature effects have been taken into account. The theoretical results obtained have been analyzed numerically for different parameter values, and the results have been presented graphically.

Effect of trapping in degenerate quantum plasmas

In the present work we consider the effect of trapping as a microscopic process in a plasma consisting of quantum electrons and nondegenerate ions. The formation of solitary structures is investigated in two cases: first when the electrons are fully degenerate and second when small temperature effects are taken into account. It is seen that not only rarefactive but coupled rarefactive and compressive solitons are obtained under different temperature conditions.