Electron Positron Ion Research Articles

Effect of quantization and positron concentration on shielding potentials in electron‐positron‐ion plasma

AbstractThe kinetic theory of plasma has been employed to compute the test‐charge potential distributions accounting for quantization effects in magnetized electron‐positron‐ion (EPI) plasmas. In this regard, the degenerate positrons and electrons are assumed to follow the Fermi‐Dirac distribution, while inertial ions are modelled by Maxwellian velocity distribution. By solving the Fourier‐transformed Vlasov–Poisson equations, a modified dielectric function and electrostatic potential is obtained. By imposing various constraints on the test‐charge speed, the potential profile has been analysed in terms of Debye–Hückel (DH), far‐field (FF), and wake‐field (WF) potentials. It has been found that the amplitude of DH and FF potentials increases by the inclusion of quantization effects, and it becomes the opposite for the WF potential profile. Furthermore, the variation of positron concentration significantly affects the DH, FF, and WF potentials. The present findings are important to understand the shielding phenomenon in degenerate multi‐species plasmas.

Propagation of ion-acoustic localized mode excitations and their modulational instability analysis in electron–positron–ion plasmas

The modulational instability of ion-acoustic waves (IAWs) in an unmagnetized multicomponent plasma is investigated, including a hot positrons, hot isothermal electrons and cold ions. Employing the reductive perturbation technique, the nonlinear Schr $$\ddot{o}$$ dinger equation (NLSE) is derived. The effects of positron concentration and temperature ratio of electron to positron significantly modify the modulational instability and its growth rate. Results show that increasing the strength of these parameters leads to localization of IAWs. Further, the exact traveling wave solutions are studied using a modified extended tanh function method. The relevance of theoretical results may be beneficent in understanding the localized electrostatic disturbances in space and astrophysical situations where electron–positron–ion plasmas are present.

Superperiodicity, chaos and coexisting orbits of ion-acoustic waves in a four-component nonextensive plasma

Superperiodicity, chaos and coexisting orbits of ion-acoustic waves (IAWs) are studied in a multi-component plasma consisting of fluid ions, q-nonextensive cold and hot electrons and Maxwellian hot positrons. The significant impacts of the system parameters on superperiodic and nonlinear periodic IAWs are presented. Considering an external periodic perturbation various types of quasiperiodic and chaotic features for IAWs are studied in different parametric ranges through time series’ plots, phase spaces and Lyapunov exponents. It has been observed that there exist some coexisting orbits for IAWs. Coexisting orbits for IAWs in a classical electron–positron–ion plasma system are reported.

Effects of finite ion inertia on phase-mixing of Langmuir oscillations in cold electron-positron-ion plasmas

We study the influences of finite ion mass on the phase-mixing process of Langmuir oscillations (LOs) in cold electron-positron-ion (EPI) plasmas. We solve the three fluid-Maxwell's equations in a perturbative way to provide an analytical estimate of phase-mixing time of LOs in such multispecies plasmas. The phase-mixing time is shown to depend on the perturbation amplitude, on the equilibrium ion-to-electron density ratio, and on the electron-to-ion mass ratio. The analytical dependence of phase-mixing time on these parameters is also discussed in various plasma limits.

Investigation of Shock Waves in Nonextensive Electron–Positron–Ion Plasma with Relativistic Ions

Nonlinear propagation of ion-acoustic (IA) shock wave in a nonextensive and relativistic plasma is investigated by deriving space fractional Korteweg–de Vries–Burgers (SFKB) equation. This unmagnetized and collisionless plasma contains relativistic thermal ions, q-distributed electrons, and positrons. A modified tanh-function method is presented to solve the obtained SFKB equation taking space fractional and relativistic parameters, electrons nonextensivity, positrons nonextensivity, and electron-to-positron temperature ratio. It is observed that the structure of the IA shock wave can be modified by space fractional parameters. On the other hand, the IA shock wave shape can be modulated using the space fractional parameter. Our results can help understand the astrophysical environments such as pulsar magnetospheres, quasars, and collimated jets.

Particle energization by high-power laser pulse in a finite-size electron–positron–ion plasma

In this paper, nonlinear laser energy absorption in a finite-size electron–positron–ion plasma is studied in detail, using a two-dimensional relativistic electromagnetic PIC simulation code. It turns out that the laser energy absorption rate in the electron–positron–ion plasma drastically depends on the positron to electron density ratio (). This can be attributed to the effects of this parameter on nonlinear phenomena related to laser absorption such as phase mixing and laser scattering. The results illustrate that phase-mixing time is reduced by increasing the defined density ratio, resulting in the enhancement of the laser energy absorption rate. As a significant result, it can be found that in a finite-size electron–positron–ion plasma the absorption rate increases with increasing as long as laser scattering from the plasma is not considerable. It is shown that for long enough times the absorption rate decreases by increasing due to stimulated instabilities. The simulation results presented on the phase mixing of nonlinear oscillations as well as on particle energization in electron–positron–ion plasmas are expected to have relevance to laboratory and astrophysical environments.

Twisted positron-acoustic wave in quantum plasmas

In this paper, we explore the existence of positron-acoustic wave (PAW) carrying orbital angular momentum (OAM) in a quantum electron-positron-ion (EPI) plasma system containing electrons, two-temperature positrons, and immobile ions as a neutralizing background. To achieve this aim, we employ the quantum hydrodynamic approach to obtain the evaluation equation of cold positrons density. By solving this equation in the paraxial limit, the Laguerre–Gaussian (LG) modes of positron perturbation are derived, and their corresponding angular momentum densities are calculated. In the following, based on numerical analyses it is found that the evolution of LG potentials and cold positrons density oscillations are greatly affected by variation of radial and angular mode numbers, relative Fermi temperature of hot species, positrons concentration, and azimuthal phase value. It is expected that the results of this study will give more insight into the positrons dynamics in dense astrophysical and laboratory plasmas.

Drift and ion acoustic waves in an inhomogeneous electron-positron-ion plasma with temperature degeneracy and exchange-correlation effects

Plasma is a complex system because of huge variation in density and temperature, on the basis of these variations, the importance of classical limit, relativistic effects and different types of quantum effects are decided. In dense plasmas, the quantum effects become important. Therefore, in the present manuscript we investigate the role of exchange correlation and pressure degeneracy effects on the propagation of drift and ion acoustic waves (IAW) in an inhomogeneous dense electron–positron-ion (EPI) plasma. Most of the work presented here is analytical and based on the quantum hydrodynamic model and Mathematica is used to draw the different plots for illustration of the results. The nonlinear vortex solution is obtained with the help of Larichev and Reznik technique. A general linear dispersion relation is derived in a degenerate plasma which gives the several limiting cases of previous studies. The drift wave and IAW driven dipolar vortex solution is discussed. It is noticed that boundedness condition for the existence of nonlinear structures is significantly modify. It is pointed out that obeying boundedness condition of the solution, the nonlinear structures can move with the drift speed or the acoustic speed or greater than both the speeds. It is also noticed that the amplitude of the structures increases by increasing the Mach number. The present study is relevant to dense plasma system, where EPI plasma exists.

Electromagnetic vortex solitons in the magnetospheres of super-Eddington AGN

Propagation and dynamics of electromagnetic vortex solitons have been studied in the electron positron ion plasmas of super-Eddington active galactic nuclei (AGN). Existence and stability of such structures is demonstrated for highly transparent AGN plasma media. Possible implications of dynamical features and corresponding observational signatures are discussed.

Hydrodynamic analysis of electrostatic counter‐streaming instability in a spin‐polarized electron–positron–ion plasma

AbstractIn this study, we present linear analysis of electrostatic counter‐streaming instability in spin‐polarized electron–positron–ion (e‐p‐i) plasma. With the aid of the separate spin evolution‐quantum hydrodynamic (SSE‐QHD) model, we derive the dispersion relation of counter‐streaming instability. We numerically solve the dispersion and find four wave solutions: Langmuir wave, positron acoustic mode, and two electron and positron spin‐dependent waves. It is noted that coupling of streaming and spin effects excites Langmuir instability and positron acoustic mode instability. However, in the absence of spin effect, only Langmuir instability will survive in e‐p‐i plasma. We have also discussed the effects of positron concentration, streaming speed, and spin polarization on the real frequency of waves and the growth rate. The present study may be helpful for understanding longitudinal wave propagation and instabilities in dense magnetized environments.

Momentum-exchange current drive by electrostatic waves in an unmagnetized collisionless plasma

For a planar electrostatic wave interacting with a single species in a collisionless plasma, momentum conservation implies current conservation. However, when multiple species interact with the wave, they can exchange momentum, leading to current drive. A simple, general formula for this driven current is derived. As examples, we show how currents can be driven for Langmuir waves in electron–positron–ion plasmas, and for ion-acoustic waves in electron–ion plasmas.

Three-Dimensional Isothermal Ion Acoustic Shock Waves in Ultra-Relativistic Degenerate Electron–Positron–Ion Magnetoplasmas

The modifications, which arise from ultra-relativistic and degenerate effects of electrons and positrons as well as the chemical potentials in the basic features of three-dimensional isothermal ion acoustic shock waves (IIASWs) propagating in magnetized electron–positron–ion (e–p–i) plasmas are studied. The cold ions are considered to be magnetized and inertial, while the small particles (i.e., electrons and positrons) are taken to obey the Fermi–Dirac statistics. The well-known reductive perturbation analysis is applied to obtain the nonlinear Zakharov–Kuznetsov–Burgers equation (NZKBE). The analytical shock wave solution is obtained by employing the tanh technique. Furthermore, the asymptotic behavior and the stability of the shock structures are discussed. In the current model, the disturbances of nonlinear isothermal ion acoustic waves are found to exhibit only monotonic IIASWs. The consequences of the chemical potential, the presence of ultra-relativistic degenerate electrons and positrons, and magnetic field on the essential properties of three-dimensional IIASWs are numerically examined. The numerical investigations give rise to significant high lights on the propagation and the dynamic behavior of IIASWs. It is found that the amplitudes of the monotonic IIASWs decrease with chemical potentials of ultra-relativistic degenerate electrons and positrons increase.

Oblique propagation of nonlinear solitary structures in electron positron ion plasmas under the influence of quantizing magnetic field

We study the propagation properties of the small amplitude nonlinear ion acoustic solitary structure in dense electron-position-ion (e-p-i) plasmas. We consider an oblique propagation of the wave with respect to the applied magnetic field. The reductive perturbation technique is employed to derive the nonlinear Zakharov-Kuznetsov (ZK) equation which describes the propagation characteristics of the ion acoustic solitary wave structures in e-p-i plasmas. The effects of different plasma parameters including the positron concentration have been invesigated. These findings may be helpful to understand the small amplitude nonlinear solitary structures that exist in the dense astrophysical environments and in the intense-laser plasma interactions.

Zakharov–Kuznetsov–Burgers equation in a magnetised non-extensive electron–positron–ion plasma

In this paper, we have studied the three-dimensional (3D) electron-acoustic waves (EAWs) in a three-component complex plasma containing q-non-extensive distributed hot electrons and positrons. The propagation characteristics of the 3D electron-acoustic (EA) shock waves under the influence of magnetic field have been studied. Our present plasma model supports the negative potential shocks. Combined action of dissipation $$(\eta )$$ , non-extensivity (q), concentration of positrons ( $$\beta $$ ), temperature ratio of cold electrons to positrons ( $$\sigma $$ ) and magnetic field ( $$\omega _c$$ ) on the EA shock waves has been studied in detail and the findings obtained here will be beneficial in future astrophysical investigations.

Alfvenic perturbations with finite Larmor radius effect in non-Maxwellian electron–positron–ion plasmas

Linear and nonlinear coupled kinetic Alfven acoustic (CKAA) waves in low-β electron–positron–ion (e-p-i) plasmas are investigated in this paper, and the main focus is on highlighting the role of non-thermal electrons and positrons that follow the generalized (r, q) distribution. In this regard, a linear dispersion relation is derived, and the effect of positron concentration and (r, q) distributed electrons and positrons is explored. Nonlinear analysis is performed by using the Sagdeev potential approach and two-potential theory. The results are compared with those of the previous studies of CKAA waves in e-p-i plasmas where electrons and positrons follow Maxwellian and kappa distributions. An important feature of our study is the observation of the existence of density dip solitons for spiky distribution. It is shown that the inclusion of positrons alters the existence regimes of the solitary structures, and, interestingly, the behavior of soliton propagation is different in the two existence regimes for increasing or decreasing concentration of positrons. Most importantly, it is shown that the spatial scales over which solitons form in e-p-i plasmas are shorter than the ones that form in e-i plasmas for compressive solitary structures. Interestingly, the situation is reversed for rarefactive solitary structures. The present study is beneficial in comprehending the linear and nonlinear propagation of CKAA waves in plasmas where positrons are present, and there is a simultaneous presence of nonthermal features in the observed distribution functions.

Cylindrical Magnetosonic Solitary Waves by Modified Korteweg–de Vries–Burgers Equation in Electron–Positron–Ion Plasma

Theoretical investigations are carried out for the cylindrical magnetosonic solitary waves in dissipative, hot electron–positron–ion plasma. By the reductive perturbation technique the modified Korteweg–de Vries–Burgers equation (mKdVB) is obtained and its approximate analytical solution is given. Using this solution, the effects of different physical parameters on magnetosonic solitary wave in cylindrical geometry are discussed. The results may have applications in laboratory and space plasmas.

Ion-acoustic gardner solitons and double layers in magnetized electron-positron-ion quantum plasma

The nonlinear propagation of ion-acoustic Gardner solitons (GSs) and double layers (DLs) in electron-positron-ion (EPI) plasma in the presence of an external static magnetic field has been examined. The Korteweg–de Vries (KdV), modified KdV (mKdV), and Gardner equations have been derived by the reductive perturbation technique. It is seen that the amplitude, polarity, speed, width of such solitons are significantly modified by the species densities and by the obliquity angle. Compressive or rarefactive KdV solitons are obtained, but only compressive solitons are obtained in the mKdV case, wherever Gardner positive and negative DLs exist. The results of our present investigation may be useful for understanding the nonlinear wave propagation in dense quantum plasmas such as those existing in white dwarfs, neutron stars and intense laser-solid matter interaction experiments as an example of laboratory plasmas.

Dynamical behaviour of non‐linear quantum ion acoustic wave in weakly magnetized electron–positron–ion plasma

AbstractIn order to investigate the propagation characteristics of linear and non‐linear ion acoustic waves (IAWs) in electron–positron–ion quantum plasma in the presence of external weak magnetic field, we have used a quantum hydrodynamic model, and degenerate statistics for the electrons and positrons are taken into account. It is found that the linear dispersion relation of the IAW was modified by the externally applied magnetic field. By using the reductive perturbation technique, a gyration‐modified Korteweg‐de Vries equation is derived for finite amplitude non‐linear IAWs. Time‐dependent numerical simulation shows the formation of an oscillating tail in front of the ion acoustic solitons in the presence of a weak magnetic field. It is also seen that the amplitude and width of solitons and oscillating tails are affected by the relevant plasma parameters such as quantum diffraction, positron concentration, and magnetic field. We have performed our analysis by extending it to account for approximate soliton solution by asymptotic perturbation technique and non‐linear analysis via a dynamical system approach. The analytical results show the distortion of the shape of the localized soliton with time, and the non‐linear analysis confirms the generation of oscillating tails.

Head-on Collision of Ion-Acoustic Solitary Waves with Two Negative Ion Species in Electron–Positron–Ion Plasmas and Production of Rogue Waves

The interactions between ion acoustic solitary waves (IASWs) are investigated considering completely ionized electron–positron–ion (e–p–i) plasmas consisting of ions with positive and two negative species, nonthermal electrons, and positrons. Two-sided Korteweg–de Vries (KdV) and modified KdV (mKdV) equations are derived using extended Poincare–Lighthill–Kuo (ePLK) reductive perturbation method. To investigate the production of ion-acoustic rogue waves (IARWs), the rational solution of nonlinear Schrodinger equation (NLSE) is derived from the mKdV equation. Two types of plasmas containing $${\text{A}}{{{\text{r}}}^{ + }}$$ , $${{{\text{F}}}^{ - }}$$ , and $${\text{SF}}_{{\text{5}}}^{ - }$$ species, as well as $${\text{SF}}_{{\text{5}}}^{ + }$$ , $${{{\text{F}}}^{ - }}$$ , and $${\text{SF}}_{{\text{5}}}^{ - }$$ species, are taken into account to study their effects on the amplitudes and phase shifts after collision, as well as the production and properties of rogue waves (RWs). It is observed during collision that a high-amplitude wave is produced in the interaction region depending on the type and parameters of plasmas. The nonthermality of electrons and positrons, electron-to-positron temperature ratio, and the density of negative ions modify the phase shift and amplitude of the waves produced during the collision of the two solitons. The amplitude of the RW for the $${\text{A}}{{{\text{r}}}^{ + }}$$ , $${{{\text{F}}}^{ - }}$$ , and $${\text{SF}}_{{\text{5}}}^{ - }$$ plasmas is found to be larger than that for the $${\text{SF}}_{{\text{5}}}^{ + }$$ , $${{{\text{F}}}^{ - }}$$ , and $${\text{SF}}_{{\text{5}}}^{ - }$$ plasmas.

Modulation instability of lower hybrid waves leading to cusp solitons in electron–positron(hole)–ion Thomas Fermi plasma

Following the idea of three‐wave resonant interactions of lower hybrid waves, it is shown that quantum‐modified lower hybrid (QLH) wave in electron–positron–ion plasma with spatial dispersion can decay into another QLH wave (where electron and positrons are activated, whereas ions remain in the background) and another ultra‐low frequency quantum‐modified ultra‐low frequency Lower Hybrid (QULH) (where ions are mobile). Quantum effects like Bohm potential and Fermi pressure on the lower hybrid wave significantly reshaped the dispersion properties of these waves. Later, a set of non‐linear Zakharov equations were derived to consider the formation of QLH wave solitons, with the non‐linear contribution from the QLH waves. Furthermore, modulational instability of the lower hybrid wave solitons is investigated, and consequently, its growth rates are examined for different limiting cases. As the growth rate associated with the three‐wave resonant interaction is generally smaller than the growth associated with the modulational instability, only the latter have been investigated. Soliton solutions from the set of coupled Zakharov and NLS equations in the quasi‐stationary regime have been studied. Ordinary solitons are an attribute of non‐linearity, whereas a cusp soliton solution featured by nonlocal nonlinearity has also been studied. Such an approach to lower hybrid waves and cusp solitons study in Fermi gas comprising electron positron and ions is new and important. The general results obtained in this quantum plasma theory will have widespread applicability, particularly for processes in high‐energy plasma–laser interactions set for laboratory astrophysics and solid‐state plasmas.