Presence Of Superthermal Electrons Research Articles

Obliquely overtaking Collisions of electron-acoustic solitary waves of inertial cold and beam electrons in the presence of superthermal electrons

Overtaking collision of the electron-acoustic solitary waves in the four-component collisionless, magnetized plasma has been investigated. The system consists of cool inertial background electrons of temperature Tc, cool inertial electron beam of temperature Tb, hot inertialess superthermal electrons modeled by a κ-distribution of temperature Th and ions. Nonlinear Korteweg–de Vries (KdV) equation that characterizing the EASWs in such a plasma model is derived. The system admits both compressive and rarefactive solitary waves. The overtaking collision of two and three-soliton solutions is investigated using Hirota’s bilinear technique. Physical parameters influence the interchange of energy caused by overtaking collisions. These parameters comprise the magnetic field, obliquity angle, the beam, cool and hot electrons number densities and temperatures, and this causes the solitons behavior to be alternated. The amplitude, and width increase as the superthermal electrons temperature increases or magnetic field decreases. The system parameters have an effect on the phase shifts as well. The current research is an attempt to shed light on the characteristics of N-soliton in the four-component collisionless, magnetized plasma that are applicable in several astrophysical plasma environments such as the Earth’s magnetosphere.

Dissipative electrostatic wave modulation in warm multi-ion dusty plasmas with superthermal electrons

Abstract A theoretical investigation has been carried out to explore the modulational instability (MI) of electrostatic waves in a warm multi-ion dusty plasma system containing positive ions, negative ions and positively or negatively charged dust in presence of superthermal electrons. With the help of the standard perturbation technique, it is found that the dynamics of the modulated wave is governed by a damped nonlinear Schrödinger equation (NLSE). Regions of MI of the electrostatic wave are precisely determined and the analytical solutions predict the formation of dissipative bright and dark solitons as well as dissipative first- and second-order rogue wave solutions. It is found that the striking features (viz., instability criteria, amplitude and width of rogue waves, etc.) are significantly modified by the effects of relevant plasma parameters such as degree of the electron superthermality, dust density, etc. The time dependent numerical simulations of the damped NLSE reveal that modulated electrostatic waves exhibit breather like structures. Moreover, phase plane analysis has been performed to study the dynamical behaviors of NLSE by using the theory of dynamical system. It is remarked that outcome of present study may provide physical insight into understanding the generation of several types of nonlinear structures in dusty plasma environments, where superthermal electrons, positive and negative ions are accountable (e.g. Saturn’s magnetosphere, auroral zone, etc.).

Interaction of electron acoustic waves in the presence of superthermal electrons in terrestrial magnetosphere

We have investigated the propagation and interaction of nonlinear electron acoustic waves (EAWs) in a plasma comprising hot (superthermal) and cold electrons and immobile ions. We have derived the Korteweg-de Vries equation for EAWs in the small amplitude limit. Employing the Hirota's Direct method, we have investigated the multisoliton solutions for electron acoustic solitary waves (EASWs). It has been found that the system under consideration admits only rarefactive electrostatic solitary structures. As the observable data are available in terms of electric field rather than electric potential, therefore, we have discussed our results in terms of bipolar electric field structures. The numerical analysis has revealed that the ratio of hot to cold electrons and superthermality of hot electrons play a crucial role in changing the amplitude of EASWs. The interaction of the two solitons and its dependence on the choice of propagation vectors, superthermality, and density ratio have also been elaborated. The results of the present study may be beneficial to comprehend the interaction between two EASWs in astrophysical and laboratory plasmas.

Evolution of dust ion acoustic soliton in the presence of superthermal electrons

Propagation of solitary wave in dusty plasmas started to draw the attention of the physicists since the early 90s. The presence of superthermal particles seems to have a great impact on such waves, as they indicate the existence of non-thermal systems. It has been observed that the superthermal population is capable of altering the nature of the plasmas waves. In the present paper, the effect of the superthermal electron population on the dust ion acoustic solitary wave has been explored. The plasma is considered un-magnetized and composed of two components of superthermal electrons (of two distinct temperature) along with positive ions, and negative dust particles. A major part of the work has been concentrated on the stability of the solitary structures considering the effect of the superthermal parameter. In addition, the dust charge has been considered as a variable and a detailed analysis has been provided on the same. The proposed plasma model is most suitable for analyzing Saturn magnetosphere and can be extended to any space plasmas with superthermal population.

Dust‐acoustic envelope solitons in super‐thermal plasmas

AbstractThe modulational instability (MI) of the dust‐acoustic waves (DAWs) in an electron‐positron‐ion‐dust plasma (containing super‐thermal electrons, positrons, and ions along with negatively charged adiabatic dust grains) is investigated by the analysis of the non‐linear Schrödinger equation (NLSE). To derive the NLSE, the reductive perturbation method was employed. Two different parametric regions for stable and unstable DAWs are observed. The presence of super‐thermal electrons, positrons, and ions significantly modifies both the stable and unstable regions. The critical wave number kc (at which MI sets in) depends on the super‐thermal electron, positron, and ion, and adiabatic dust concentrations.

Dust-acoustic shock waves in a dusty plasma with non-thermal ions and super-thermal electrons

The propagation of dust-acoustic shock waves (DASWs) in a collisionless unmagnetized dusty plasma (containing super-thermal electrons of two distinct temperatures, non-thermal ions, and a negatively charged viscous dust fluid) has been theoretically investigated by deriving and solving the nonlinear Burgers' equation. It has been observed that the viscous force acting on the dust fluid is a source of dissipation, and is responsible for the formation of DASWs, and that the basic features (viz., amplitude, polarity, width, etc.) of the DASWs are significantly modified by the presence of super-thermal electrons and non-thermal ions. The possible applications of this investigation in Earth's mesosphere, the solar atmosphere, Saturn's magnetosphere, etc., have also been briefly addressed.

Head-on collision of two dust ion acoustic solitary waves in a weakly relativistic multicomponent superthermal plasma

A head-on collision between two dust ion acoustic solitary waves (DIASWs) travelling in the opposite direction in a weakly relativistic plasma composed of four distinct particle populations, namely, weakly relativistic ion fluid, superthermal electrons as well as positrons, and immobile dust, is investigated. By employing extended Poincaré-Lighthill-Kuo method, two Korteweg-de Vries (KdV) equations are derived. The analytical phase shift after a head-on collision of two dust ion acoustic (DIA) solitary waves is also obtained. The combined effects of relativistic factor (β), electron to positron temperature ratio (α), ion to electron temperature ratio (σ), positron to electron density ratio (P), dust density ratio (d), and superthermality of electrons as well as positrons (via κ) on the phase shifts are numerically studied. All these physical parameters have also changed the potential amplitude and the width of colliding solitary waves. It is found that the presence of superthermal electrons as well as positrons and dust grains has emphatic influence on the phase shifts and potential pulse profiles of compressive DIA solitons. Our results are general and may be helpful in understanding a head-on collision between two DIASWs in astrophysical and laboratory plasmas, especially the interaction of pulsar relativistic winds with supernova ejecta that produces the superthermal particles and relativistic ions.

Fluid simulation of dispersive and nondispersive ion acoustic waves in the presence of superthermal electrons

One-dimensional fluid simulation is performed for the unmagnetized plasma consisting of cold fluid ions and superthermal electrons. Such a plasma system supports the generation of ion acoustic (IA) waves. A standard Gaussian type perturbation is used in both electron and ion equilibrium densities to excite the IA waves. The evolutionary profiles of the IA waves are obtained by varying the superthermal index and the amplitude of the initial perturbation. This simulation demonstrates that the amplitude of the initial perturbation and the superthermal index play an important role in determining the time evolution and the characteristics of the generated IA waves. The initial density perturbation in the system creates charge separation that drives the finite electrostatic potential in the system. This electrostatic potential later evolves into the dispersive and nondispersive IA waves in the simulation system. The density perturbation with the amplitude smaller than 10% of the equilibrium plasma density evolves into the dispersive IA waves, whereas larger density perturbations evolve into both dispersive and nondispersive IA waves for lower and higher superthermal index. The dispersive IA waves are the IA oscillations that propagate with constant ion plasma frequency, whereas the nondispersive IA waves are the IA solitary pulses (termed as IA solitons in the stability region) that propagate with the constant wave speed. The characteristics of the stable nondispersive IA solitons are found to be consistent with the nonlinear fluid theory. To the best of our knowledge, this is the first fluid simulation study that has considered the superthermal distributions for the plasma species to model the electrostatic solitary waves.

Dispersive Alfvén waves in a plasma with anisotropic superthermal particles

The dispersion of dispersive Alfvén wave in a low β plasma with anisotropic superthermal particles modeled by a bi-nonextensive distribution is derived from a kinetic way. The effect of anisotropic temperature on inertial Alfvén wave is so small that it is negligible. However, it will play an important role on the property of kinetic Alfvén wave (KAW). The numerical results reveal that the presence of superthermal electrons in the small wavenumber limit will lead the damping rate of the KAW bigger than the one with Maxwellian distribution. Whereas, the damping rate of KAW in the large wavenumber limit will decrease with the presence of superthermal electrons. When the effect of electron anisotropic temperature overwhelms the effect of finite ion gyroradius in the small wavenumber regime, the damping rate of KAW grows with the presence of electron temperature anisotropy. On the other hand, when the effects of finite ion gyroradius play a dominant role in the large wavenumber regime, the damping rate of KAW increases with the effective perpendicular and parallel electron temperatures.

Influence of Non-Maxwellian Particles on Dust Acoustic Waves in a Dusty Magnetized Plasma

In this paper an investigation into dust acoustic solitary waves (DASWs) in the presence of superthermal electrons and ions in a magnetized plasma with cold dust grains and trapped electrons is discussed. The dynamic of both electrons and ions is simulated by the generalized Lorentzian (κ) distribution function (DF). The dust grains are cold and their dynamics are studied by hydrodynamic equations. The basic set of fluid equations is reduced to modified Korteweg-de Vries (mKdV) equation using Reductive Perturbation Theory (RPT). Two types of solitary waves, fast and slow dust acoustic soliton (DAS) exist in this plasma. Calculations reveal that compressive solitary structures are possibly propagated in the plasma where dust grains are negatively (or positively) charged. The properties of DASs are also investigated numerically.

Nonplanar ion-acoustic shocks in electron–positron–ion plasmas: Effect of superthermal electrons

Ion-acoustic shock waves (IASWs) in a homogeneous unmagnetized plasma, comprising superthermal electrons, positrons, and singly charged adiabatically hot positive ions are investigated via two-dimensional nonplanar Kadomstev–Petviashvili–Burgers (KPB) equation. It is found that the profiles of the nonlinear shock structures depend on the superthermality of electrons. The influence of other plasma parameters such as, ion kinematic viscosity and ion temperature, is discussed in the presence of superthermal electrons in nonplanar geometry. It is also seen that the IASWs propagating in cylindrical/spherical geometry with transverse perturbation will be deformed as time goes on.

Dust acoustic solitary structures in multidust fluids superthermal plasma

An investigation has been made to study the properties of large-amplitude electrostatic solitary waves in dusty plasma containing both negatively and positively charged dust fluids in the presence of superthermal electrons and ions. The energy balance equation is derived by using the Sagdeev pseudopotential approach. The influence of the physical parameters (e.g., superthermality of electrons or ions, density concentration of positive and negative dust particles, solitary speed) on the amplitude of dust acoustic solitary waves has been discussed in detail. It is observed that there exists a critical value of density, below which negative potential solitary structures exist and above which positive potential solitary structures exist.

Dust acoustic soliton and double layers with streaming dust and superthermal particles

Dust acoustic waves are investigated in plasma system containing dynamic and streaming dust, supertherrmal electrons and ions. Linear and nonlinear studies are carried out and elaborated with the help of parameters taken for Saturn’s F-ring. An energy integral equation is obtained by using the Sagdeev potential approach, and results are displayed by solving it analytically and numerically. The dependence of nonlinear structures on κ values, the ratio of electron to dust equilibrium densities μed, Mach number M, and dust streaming speed vd0 have been presented. The streaming speed appears as a destructive partner for the Mach number M in the pseudoenergy equation and hence plays a dominant modifying role in the formation of nonlinear structures. It plays a destructive role for some of the solitons and works as a source, for the emergence of new solitons (region). Formation of double layers are also investigated and shown that the amplitude, width and existence of double layers structures are predominantly affected by the presence of superthermal electrons, ions, and streaming dust beam.

Effect of ion temperature on ion-acoustic solitary waves in a magnetized plasma in presence of superthermal electrons

Obliquely propagating ion-acoustic soliatry waves are examined in a magnetized plasma composed of kappa distributed electrons and fluid ions with finite temperature. The Sagdeev potential approach is used to study the properties of finite amplitude solitary waves. Using a quasi-neutrality condition, it is possible to reduce the set of equations to a single equation (energy integral equation), which describes the evolution of ion-acoustic solitary waves in magnetized plasmas. The temperature of warm ions affects the speed, amplitude, width, and pulse duration of solitons. Both the critical and the upper Mach numbers are increased by an increase in the ion temperature. The ion-acoustic soliton amplitude increases with the increase in superthermality of electrons. For auroral plasma parameters, the model predicts the soliton speed, amplitude, width, and pulse duration, respectively, to be in the range of (28.7–31.8) km/s, (0.18–20.1) mV/m; (590–167) m, and (20.5–5.25) ms, which are in good agreement with Viking observations.

Characteristics of ion acoustic solitary waves in a negative ion plasma with superthermal electrons

The behavior of ion acoustic solitons in a plasma including positive and negative ions and kappa distributed electrons is studied, using both small amplitude and arbitrary amplitude approaches. The existence regions of compressive and rarefactive solitons will depend on negative to positive ion density ratio (ν) and kappa parameter as well as positive to negative ion mass ratio (Q). The numerical analysis of Sagdeev potential shows that for a chosen plasma with fixed Q, the existence regime of compressive solitons is decreased (increased) by increasing density ratio (kappa parameter), while for rarefactive solitons these conditions are quite opposite. Additionally, the possibility of propagation of both compressive and rarefactive subsonic solitons is investigated. It is found that by increasing negative ions, the existence domains of subsonic solitons are decreased, so that in excess of negative ions subsonic solitons will not propagate even at the presence of superthermal electrons. Indeed, there is a critical negative ion density ratio for all values of kappa, above that only supersonic solitons are observed. Furthermore, in addition to the previous results based on Cairns-distributed electrons [R. A. Cairns et al., Geophys. Res. Lett. 22, 2709 (1995)], which predicted that both compressive and rarefactive solitons can coexist simultaneously, we have also found the regions of ν and κ in which either positive or negative potentials are permitted (i.e., not together). This research will be helpful in understanding the properties of space and laboratory plasmas containing negative ions with energetic electrons.

Linear and nonlinear dynamics of current-driven waves in dusty plasmas

The linear and nonlinear dynamics of a recently proposed plasma mode of dusty plasma is studied using kappa distribution for electrons. This electrostatic wave can propagate in the plasma due to the sheared flow of electrons and ions parallel to the external magnetic field in the presence of stationary dust. The coupling of this wave with the usual drift wave and ion acoustic wave is investigated. D'Angelo's mode is also modified in the presence of superthermal electrons. In the nonlinear regime, the wave can give rise to dipolar vortex structures if the shear in flow is weaker and tripolar vortices if the flow has steeper gradient. The results have been applied to Saturn's magnetosphere corresponding to negatively charged dust grains. But the theoretical model is applicable for positively charged dust as well. This work will be useful for future observations and studies of dusty environments of planets and comets.

Arbitrary dust ion acoustic soliton with streaming ions and superthermal electrons

The dynamical properties of dust-ion acoustic wave excited due to the streaming of ions and by the presence of superthermal electrons following the κ distribution function are discussed. An energy integral equation involving the Sagdeev potential is derived, and the basic properties of large amplitude solitary structures are investigated. The numerical results are elaborated by employing the parameters of mesospheric noctilucent clouds. Due to ion streaming, a regime of the existence of new solitons will take place and we found that this plays a destructive role for some of the solitons that were observable at rather lower streaming or in the absence of streaming of ions. It is also found that the presence of ion beams causes breaking up of the solitary waves into a new regime of solitons.

Drift and ion acoustic wave driven vortices with superthermal electrons

Linear and nonlinear analysis of coupled drift and acoustic mode is presented in an inhomogeneous electron-ion plasma with κ-distributed electrons. A linear dispersion relation is found which shows that the phase speed of both the drift wave and the ion acoustic wave decreases in the presence of superthermal electrons. Several limiting cases are also discussed. In the nonlinear regime, stationary solutions in the form of dipolar and monopolar vortices are obtained. It is shown that the condition for the boundedness of the solution implies that the speed of drift wave driven vortices reduces with increase in superthermality effect. Ignoring density inhomogeniety, it is investigated that the lower and upper limits on the speed of the ion acoustic driven vortices spread with the inclusion of high energy electrons. The importance of results with reference to space plasmas is also pointed out.

Modulational instability of electron-acoustic waves in plasmas with superthermal electrons

The propagation of electron-acoustic waves (EAWs) in plasmas composed of inertial cold electrons, hot superthermal electrons, and stationary ions is investigated. By means of the reduction perturbation technique, a nonlinear Schrödinger equation is derived and the modulation instability of EAW is analyzed, where the superthermal parameter is found to be of significant importance. It is shown that the presence of superthermal electrons enhances the critical wave number of the modulational instability of EAWs. Besides, due to the presence of the superthermal electrons, EAWs are stable on a vaster region. Moreover, the modulational instability growth rate is lower for a larger population of superthermal electrons. Further, it is shown that increasing values of the relative density ratio α = ne0/nc0 shifts the instability domain to lower values of wave number k.

Ion acoustic shock waves in presence of superthermal electrons and interaction of classical positron beam

The effect of positron beam on the ion-acoustic shock wave is studied. The plasma system under-consideration consists of inertial ions and superthermal electrons and the positron beam with classical streaming velocities. Kinematic viscosity of the ions component is responsible of the dissipation in plasma system. The Burgers equation has been derived by employing the reductive perturbation method. It is noticed that both the amplitude and steepness of the ion-acoustic shock wave accrue, as the spectral index of the superthermal electrons, and concentration of impinging positron beam are enhanced. However, the shock amplitude is found to diminish as the beam streaming velocity and temperature ratio of positrons to electrons are increased in the plasma system. Our findings may be helpful in the understanding of laboratory beam plasma interaction experiments as well as the space and astrophysical plasmas with effects of superthermality and interacting beam.