Electron-acoustic Solitary Waves Research Articles

Electron acoustic waves in atmospheric magnetized plasma

Propagation of electron acoustic solitary waves is studied in magnetized plasmas consisting of hot and cold electrons and stationary ions in the presence of varying magnetic field. We show that a space dependent magnetic field adds a dissipative term in the wave equation of motion without presenting known dissipation sources. Localized waves propagating in such space dependent magnetic field are governed by the modified KdV-Burgers equation. The numerical results show that, this phenomenon leads to the formation of oscillatory backward moving shock waves in the plasma. Characters of shock profile, according to the plasma parameters are discussed.

Behavior of Electron Acoustic Solitary Waves in an Unmagnetized Quantum Plasma Containing Two-Temperature Electrons

Behavior of Electron Acoustic Solitary Waves in an Unmagnetized Quantum Plasma Containing Two-Temperature Electrons

Properties of Electron-Acoustic Solitary Waves for Weak Relativistic Degeneracy Pressure at Critical Regime

Properties of Electron-Acoustic Solitary Waves for Weak Relativistic Degeneracy Pressure at Critical Regime

Study of Electron-Acoustic Solitary Waves in Ultra-relativistic Degenerate Quantum Plasma with Statistically Distinct Electrons

Study of Electron-Acoustic Solitary Waves in Ultra-relativistic Degenerate Quantum Plasma with Statistically Distinct Electrons

Generation of series of electron acoustic solitary wave pulses in plasma

One-dimensional fluid simulation is used to investigate the generation of electron-acoustic solitary waves (EASWs) in three-species plasma. We consider an unmagnetized collisionless plasma consisting of cold electrons, hot electrons, and ions. The Gaussian perturbations in the equilibrium electron and ion densities are used to excite the waves in the plasma. This simulation demonstrates the generation of a series of EASW pulses in this three-species plasma through the process of wave breaking. We investigate the behavior of the ponderomotive potential, frequency, and force associated with electrons and ions during the process of the wave breaking. We observed that the ponderomotive potential of the hot electron, which is the driving species for the electron acoustic waves, peaks at the time of wave breaking. The variation of the maximum ponderomotive force acting spatially on the leading and trailing edges of the hump in the cold and hot electron and ion fluid densities shows the maximum imbalance in the magnitude of the ponderomotive force acting on both sides of the hot electron density hump at the time of wave breaking. This reveals that the imbalanced ponderomotive force acting on the hot electron fluid is responsible for the breaking of the electron acoustic wave in plasma. Furthermore, it is observed that the wave breaking process occurs at an earlier time if the hot electron temperature is increased.

Obliquely propagating electron-acoustic solitary waves in magnetized plasmas: the role of trapped superthermal electrons

The properties of obliquely propagating electron-acoustic solitary waves (OPEASWs) have been investigated in a magnetized superthermal plasma (containing inertial cold electron species, inertialess electrons following Vasyliunas-Schamel distribution function, and static ions) via the fluid dynamical approach. The reductive perturbation technique is employed to derive the Schamel equation and the solitary wave solution of the Schamel equation is used to examine the basic features of small but finite amplitude OPEASWs in such a magnetized plasma in the presence of trapped k-superthermal hot electron population. The basic features (width, amplitude, speed, etc.) of OPEASWs are found to be significantly modified by the different plasma configuration parameters, such as plasma superthermality, obliqueness, the particle trapping effect, and external magnetic field effect. The nature of electrostatic disturbances, that may propagate in different realistic space and laboratory plasma systems (e.g., in Saturn ring), is briefly discussed.

Interaction phenomena and effect of higher order dispersion on electron acoustic solitary waves in weakly relativistic regimes

AbstractThe interaction phenomena of electron acoustic solitary waves (EASWs) and the higher order correction of Korteweg‐de Vries (KdV) equations (KdVEs) have investigated in unmagnetized collisionless plasma system consisting of relativistic cold electrons and electron beams, non‐relativistic Maxwellian hot electrons and stationary ions. To understand the physical issues concerned, the two‐sided KdVEs using extended Poincaré‐Lighthill‐Kue (ePLK) method are derived taking the higher order correction into consideration. The analyses reveal that the widths and amplitudes of EASWs (as obtain from KdVEs) are decreasing with plasma parameters. The plasma parameters are responsible for the modification of KdV‐soliton structure. It is found that the narrowness of width and the steepness of dip of the solitons become more pronounced and the electric field behaves like semi‐kink solitons due to the higher order correction of KdVEs. Dip shape rarefactive soliton becomes pronounced by plasma parameters. The phase shifts of EASWs are also enhanced due to the effects of plasma species temperatures and density ratios.

Formation of Asymmetric Electron Acoustic Double Layers in the Earth's Inner Magnetosphere

AbstractThe Van Allen Probes have observed both symmetric and asymmetric bipolar electric field structures in the Earth's inner magnetosphere. In general, the symmetric bipolar structures are identified as electron‐phase space holes, whereas the asymmetric structures are interpreted as electron acoustic double layers (EADLs). The generation mechanism of these EADLs is not entirely understood yet. We have modeled the EADLs observed on 13 November 2012 by Van Allen Probe‐B. We performed a fluid simulation of the EADLs and tracked their formation and evolution in the simulation. We found that the localized depletion and enhancement in the electron populations act as a perturbation to excite the symmetric bipolar electron acoustic solitary waves, which later evolve into the EADLs. The Ponderomotive force is found to be the main driver behind transformation of the symmetric electron acoustic solitary waves to EADLs via formation of the electron acoustic shocks.

Propagation of Solitary Waves and Double-Layers in Electron–Positron Pair Plasmas with Stationary Ions and Nonextensive Electrons

Based on reductive perturbation theory, the nonlinear structure of non-extensive multispecies plasma containing hot electrons, adiabatic cold electrons, cold positrons and ions has been investigated via different nonlinear KdV, mKdV and Gardner’s equations. It is shown that the formation and properties of electron acoustic solitary waves and double-layer can exist in such plasma system depending on some relevant physical parameters such as electron and positron density ratios, electrons temperatures ratio and non-extensive parameter. The existence conditions of these types of waves are extensively discussed. The obtained results may be useful in improving and understanding the propagation of the nonlinear electron waves in space plasma, Earth’s magnetosphere and solar wind.

Ion acoustic super solitary waves in a magnetized plasma

Ion acoustic super solitary waves have been derived for a three component magnetized plasma consisting of warm fluid ions and two different temperature electrons having Boltzmann distributions by using the Sagdeev pseudopotential technique. The result exhibits similar traits of the recently reported electron acoustic super solitary wave in a magnetized plasma [Kamalam et al., J. Plasma Phys. 84, 905840406 (2018)]. This is the first report of super solitary waves for a low frequency wave in a magnetized plasma. This prediction might be useful to analyze the non-conventional structures in the low altitude auroral regions in the Earth's magnetosphere.

Construction of solitary wave solutions to the nonlinear modified Kortewege-de Vries dynamical equation in unmagnetized plasma via mathematical methods

In this research, we consider the propagation of one-dimensional nonlinear behavior in a unmagnetized plasma. By using the reductive perturbation technique to formulate the nonlinear mathematic model which is modified Kortewege-de Vries (mKdV), we apply the extended form of two methods, which are extended auxiliary equation mapping and extended direct algebraic methods, to investigate the new families of electron-acoustic solitary wave solutions of mKdV. These new exact traveling and solitary wave solutions which represent the electrostatic potential for mKdV and also the graphical representation of electrostatic potential are shown with the aid of Mathematica.

Existence of electron acoustic solitary waves in relativistic limit

The nonlinear relativistic dynamics of electron acoustic waves (EAWs) in collisionless, unmagnetized plasma comprising cold inertial electrons, hot Boltzmann distributed electrons, and stationary ions are studied. The Sagdeev pseudopotential technique is employed to discuss the effect of equilibrium plasma species density and temperature of the hot electrons on the relativistic solitary wave solutions. In exploring the electron acoustic soliton characteristics, we encounter only negative polarity solitons which are found to exist in a restricted range of the physical parameter space of the system. In addition, we extend our analysis to demonstrate the wave breaking phenomena of EAW and estimate the maximum sustainable electric field amplitude of this mode considering the relativistic electron mass variation effect.

Electron acoustic super solitary waves in a magnetized plasma

An electron acoustic super solitary wave has been derived using the Sagdeev pseudopotential technique for a four component magnetized plasma consisting of the beam and bulk fluid electrons and two ions with Maxwell Boltzmann distributions. This is the first theoretical report of a super solitary wave in a magnetized plasma which has no direct association with the singularity of the pseudopotential. It shows a narrow and spiky subwell near the low potential which causes the lateral inversion of the wiggle for the bipolar electric field vis-á-vis the unmagnetized plasma. An analytical formalism was developed to identify these novel kinds of super solitary waves and their transition processes have been characterized. It was observed that the super solitary wave is directly influenced by the singularity of the pseudopotential lying in the vicinity of the solution. The first ever prediction of the electron acoustic super solitary wave raises the possibility of its application to the interpretation of the satellite observations of the electrostatic field data.

Electron beam-plasma interaction and electron-acoustic solitary waves in a plasma with suprathermal electrons

Suprathermal electrons and inertial drifting electrons, so called electron beam, are crucial to the nonlinear dynamics of electrostatic solitary waves observed in several astrophysical plasmas. In this paper, the propagation of electron-acoustic solitary waves (EAWs) is investigated in a collisionless, unmagnetized plasma consisting of cool inertial background electrons, hot suprathermal electrons (modeled by a κ-type distribution), and stationary ions. The plasma is penetrated by a cool electron beam component. A linear dispersion relation is derived to describe small-amplitude wave structures that shows a weak dependence of the phase speed on the electron beam velocity and density. A (Sagdeev-type) pseudopotential approach is employed to obtain the existence domain of large-amplitude solitary waves, and investigate how their nonlinear structures depend on the kinematic and physical properties of the electron beam and the suprathermality (described by κ) of the hot electrons. The results indicate that the electron beam can largely alter the EAWs, but can only produce negative polarity solitary waves in this model. While the electron beam co-propagates with the solitary waves, the soliton existence domain (Mach number range) becomes narrower (nearly down to nil) with increasing the beam speed and the beam-to-hot electron temperature ratio, and decreasing the beam-to-cool electron density ratio in high suprathermality (low κ). It is found that the electric potential amplitude largely declines with increasing the beam speed and the beam-to-cool electron density ratio for co-propagating solitary waves, but is slightly decreased by raising the beam-to-hot electron temperature ratio.

Electron acoustic nonlinear structures in planetary magnetospheres

In this paper, we have studied linear and nonlinear propagation of electron acoustic waves (EAWs) comprising cold and hot populations in which the ions form the neutralizing background. The hot electrons have been assumed to follow the generalized (r,q) distribution which has the advantage that it mimics most of the distribution functions observed in space plasmas. Interestingly, it has been found that unlike Maxwellian and kappa distributions, the electron acoustic waves admit not only rarefactive structures but also allow the formation of compressive solitary structures for generalized (r,q) distribution. It has been found that the flatness parameter r, tail parameter q, and the nonlinear propagation velocity u affect the propagation characteristics of nonlinear EAWs. Using the plasmas parameters, typically found in Saturn's magnetosphere and the Earth's auroral region, where two populations of electrons and electron acoustic solitary waves (EASWs) have been observed, we have given an estimate of the scale lengths over which these nonlinear waves are expected to form and how the size of these structures would vary with the change in the shape of the distribution function and with the change of the plasma parameters.

Effect of electron temperature on small-amplitude electron acoustic solitary waves in non-planar geometry

Effects of electron temperature on the propagation of electron acoustic solitary waves in plasma with stationary ions, cold and superthermal hot electrons is investigated in non-planar geometry employing reductive perturbation method. Modified Korteweg–de Vries equation is derived in the small amplitude approximation limit. The analytical and numerical calculations of the KdV equation reveal that the phase velocity of the electron acoustic waves increases as one goes from planar to non planar geometry. It is shown that the electron temperature ratio changes the width and amplitude of the solitary waves and when electron temperature is not taken into account,our results completely agree with the results of Javidan & Pakzad (2012). It is found that at small values of \(\tau \), solitary wave structures behave differently in cylindrical (\(\text {m} = 1\)), spherical (\(\text {m} = 2\)) and planar geometry (\(\text {m} = 0\)) but looks similar at large values of \(\tau \). These results may be useful to understand the solitary wave characteristics in laboratory and space environments where the plasma have multiple temperature electrons.

Electron-acoustic solitary waves in the Earth's inner magnetosphere

The broadband electrostatic turbulence observed in the inner magnetosphere is produced by large-amplitude electrostatic solitary waves of generally two types. The solitary waves with symmetric bipolar parallel (magnetic field-aligned) electric field are electron phase space holes. The solitary waves with highly asymmetric bipolar parallel electric field have been recently shown to correspond to the electron-acoustic plasma mode (existing due to two-temperature electron population). Through theoretical and numerical analysis of hydrodynamic and modified Korteweg-de Vries equations, we demonstrate that the asymmetric solitary waves appear due to the steepening of initially quasi-monochromatic electron-acoustic perturbation arrested at some moment by collisionless dissipation (Landau damping). The typical steepening time is found to be from a few to tens of milliseconds. The steepening of the electron-acoustic waves has not been reproduced in self-consistent kinetic simulations yet, and factors controlling the formation of steepened electron-acoustic waves, rather than electron phase space holes, remain unclear.

Analytical electron acoustic solitary wave solution for the forced KdV equation in superthermal plasmas

Analytical electron acoustic solitary wave (EASW) solution is investigated in the presence of periodic force for an unmagnetized plasma consisting of cold electron fluid, superthermal hot electrons, and stationary ions. Employing the reductive perturbation technique, the forced Korteg-de Vries (KdV) equation is derived for electron acoustic waves. For the first time, an analytical solution for EASWs is derived in the presence of periodic force. The effects of the ratio between hot electron and cold electron number densities at equilibrium (α), spectral index (κ), speed of the traveling wave (M), strength (f0), and frequency (ω) of the periodic force are studied on the analytical solution of EASWs. It is observed that the parameters α, κ, M, f0, and ω affect significantly the structures of the electron acoustic solitary waves. The results may have relevance in laboratory plasmas as well as in space plasma environments.

Electron-acoustic solitary waves in a beam plasma with electron trapping and nonextensivity effects

A theoretical investigation is carried out for understanding the properties of electron-acoustic solitary waves (EASWs) in a beam plasma whose constituents are a cold beam electron fluid, hot nonextensive electrons obeying a vortex-like distribution with nonextensive factor q, and stationary ions. An energy integral (Schamel KdV) equation is derived by employing pseudo-potential (reductive perturbation) approach. The presence of nonextensive q-distributed hot trapped electrons and cold electron beam has been shown to influence the soliton structure quite significantly. The nonlinear dispersion relation is derived to analyze the dependency of the electron acoustic solitary wave quantities. From the analysis of our results, it is shown that the present plasma model supports the compressive EASWs. As the real plasma situations are observed with plasma species having a relative flow, so our present analysis should be useful for understanding the electrostatic solitary structures observed in the dayside auroral zone and other regions of the magnetosphere.

Effects of nonextensivity on the electron-acoustic solitary structures in a magnetized electron−positron−ion plasma

Obliquely propagating electron-acoustic solitary waves (EASWs) in a magnetized electron−positron−ion plasma (containing nonextensive hot electrons and positrons, inertial cold electrons, and immobile positive ions) are precisely investigated by deriving the Zakharov–Kuznetsov equation. It is found that the basic features (viz. polarity, amplitude, width, phase speed, etc.) of the EASWs are significantly modified by the effects of the external magnetic field, obliqueness of the system, nonextensivity of hot positrons and electrons, ratio of the hot electron temperature to the hot positron temperature, and ratio of the cold electron number density to the hot positron number density. The findings of our results can be employed in understanding the localized electrostatic structures and the characteristics of EASWs in various astrophysical plasmas.