In a recent one-dimensional numerical fluid simulation study [Saxena et al., Phys. Plasmas 13,032309 (2006)], it was found that an instability is associated with a special class of one-dimensional nonlinear solutions for modulated light pulses coupled to electron plasma waves in a relativistic cold plasma model. It is shown here that the instability can be understood on the basis of the stimulated Raman scattering phenomenon and the occurrence of density bursts in the trailing edge of the modulated structures are a manifestation of an explosive instability arising from a nonlinear phase mixing mechanism.
The existence of standing high frequency electromagnetic (EM) solitons in a fully degenerate overdense electron plasma is studied applying relativistic hydrodynamics and Maxwell equations. The stable soliton solutions are found in both relativistic and nonrelativistic degenerate plasmas.
The existence of soliton-like electromagnetic (EM) distributions in a fully degenerate electron-positron plasma is studied applying relativistic hydrodynamic and Maxwell equations. For circularly polarized wave it is found that the soliton solutions exist both in relativistic as well as nonrelativistic degenerate plasmas. Plasma density in the region of soliton pulse localization is reduced considerably. The possibility of plasma cavitation is also shown.
We investigate the existence of envelope soliton solutions in collisionless quantum plasmas, using the quantum-corrected Zakharov equations in the kinetic case, which describes the interaction between high frequency Langmuir waves and low frequency plasma density variations. We show the role played by quantum effects in the nonlinearity/dispersion balance leading to the formation of soliton solutions of the quantum-corrected nonlinear Schrodinger (QNLS) equation.
Propagation of Langmuir solitons in inhomogeneous plasmas is investigated numerically. Through numerical simulation solving Zakharov equations, the solitons are accelerated toward the low density side. As a consequence, isolated cavities moving at ion sound velocities are emitted. When the acceleration is further increased, solitons collapse and the cavities separate into two lumps released at ion sound velocities. The threshold is estimated by an analogy between the soliton and a particle overcoming the self-generated potential well.
The passage of a magnetosonic (MS) soliton in a cold plasma leads to the displacement of charged particles in the direction of a compressive pulse and in the opposite direction of a rarefaction pulse. In the overdense plasma limit, the displacement induced by a weakly nonlinear MS soliton is derived analytically. This result is then used to derive an asymptotic expansion for the displacement resulting from the bouncing motion of a MS soliton reflected back and forth in a vacuum-bounded cold plasma slab. Particles' displacement after the pulse energy has been lost to the vacuum region is shown …
The dynamics of the ultra-intense circularly polarized solitons under inhomogeneous plasmas are examined. The interaction is modeled by the Maxwell and relativistic hydrodynamic equations and is solved with fully implicit energy-conserving numerical scheme. It is shown that a propagating weak soliton can be decreased and reflected by increasing plasma background, which is consistent with the existing studies based on hypothesis of weak density response. However it is found that ultra-intense soliton is well trapped and kept still when encountering increasing background. Probably, this founding…
The evolution of electromagnetic (EM) solitons due to nonlinear coupling of circularly polarized intense laser pulses with low-frequency electron-acoustic perturbations is studied in relativistic degenerate dense astrophysical plasmas with two groups of electrons: a sparse population of classical relativistic electrons and a dense population of relativistic degenerate electron gas. Different forms of localized stationary solutions are obtained and their properties are analyzed. Using the Vakhitov-Kolokolov stability criterion, the conditions for the existence and stability of a moving EM solit…
The existence of localized electromagnetic structures is discussed in the framework of the 1-dimensional relativistic Maxwell-fluid model for a cold plasma with immobile ions. New partially localized solutions are found with a finite-difference algorithm designed to locate numerically exact solutions of the Maxwell-fluid system. These solutions are called quasi-solitons and consist of a localized electromagnetic wave trapped in a spatially extended electron plasma wave. They are organized in families characterized by the number of nodes $p$ of the vector potential and exist in a continuous ran…
The existence of magnetosonic solitons in dusty plasmas is investigated. The nonlinear magnetohydrodynamic equations for a warm dusty magnetoplasma are thus derived. A solution of the nonlinear equations is presented. It is shown that, due to the presence of dust, static structures are allowed. This is in sharp contrast to the formation of the so called shocklets in usual magnetoplasmas. A comparatively small number of dust particles can thus drastically alter the behavior of the nonlinear structures in magnetized plasmas.
A case of moving one-dimensional electromagnetic (EM) solitons formed in a relativistic interaction of a linearly polarized laser light with underdense cold plasma is investigated. The relativistic Lorentz force in an intense laser light pushes electrons into longitudinal motion generating coupled longitudal-transverse wave modes. In a weakly relativistic approximation these modes are well described by a dynamical equation of the generalized nonlinear Schrodinger type, with two additional nonlocal terms [1]. An original analytical solution for a moving EM soliton case is here calculated in an …
The propagation characteristics and interactions between the dust acoustic (DA) one and multi solitons in an unmagnetized dusty plasmas composing negatively charged mobile dust, Boltzmann distributed electrons, nonextensive distributed cold and nonthermal distributed hot ions are studied. The well known extended Poincar Lighthill Kuo (PLK) method is employed to derive the two sided Korteweg de Vries (KdV) equations. The solutions of KdV equations are constructed using the Hirota method both for one and multi solitons. The phase shifts are determined for the interaction of one, two and three DA…
We study the evolution of nonlinear ion acoustic wave excitations due to a moving charged source in a plasma. Our numerical investigations of the full set of cold fluid equations goes beyond the usual weak nonlinearity approximation and shows the existence of a rich variety of solutions including wakes, precursor solitons and pinned solitons that travel with the source velocity. These solutions represent a large amplitude generalization of solutions obtained in the past for the forced Korteweg deVries equation and can find useful applications in a variety of situations in the laboratory and in…
The expansion of electromagnetic post-solitons emerging from the interaction of a 30 ps, $3\times 10^{18}$ W cm$^{-2}$ laser pulse with an underdense deuterium plasma has been observed up to 100 ps after the pulse propagation, when large numbers of post-solitons were seen to remain in the plasma. The temporal evolution of the post-solitons has been accurately characterized with a high spatial and temporal resolution. The observed expansion is compared to analytical models and three dimensional particle-in-cell results providing indication of the polarisation dependence of the post-soliton dyna…
A Self-Consistent Model of Kinetic Alfven Solitons in Pulsar Wind Plasma: Linking Soliton Characteristics to Pulsar Observables
School of Computing and Artificial Intelligence, Southwest Jiaotong University（西南交通大学计算机科学与人工智能学院）；School of Physical Science and Technology, Southwest Jiaotong University（西南交通大学物理科学与技术学院）；Department of Physics, Guru Nanak Dev University（古鲁纳克德夫大学物理系）；Department of Physics, Government College for Women, Udhampur（乌德汉普尔女子政府学院物理系）
This paper presents the detailed study of the controlled experimental observation and characterization of Ion Acoustic soliton in the quiescent argon plasma produced by filamentary discharge and confined in a multi-pole line cusp magnetic field device named Multi-pole line Cusp Plasma Device (MPD). In this system, the electrostatic fluctuations are found to be less than 1%, a characteristic of quiescent plasma. Ion acoustic soliton has been excited in MPD, and its propagation velocity and width of them are measured experimentally and compared with the 1-D Korteweg-de Vries (KdV) equation. The …
Propagation of ion-acoustic solitary waves (IASWs) is studied using the hydrodynamic equations coupled with the Poisson equation in a warm plasma consisting of adiabatic ions and superthermal (Kappa distributed) electrons in presence of an electron-beam component. In the linear limit, the dispersion relation for ion-acoustic (IA) waves is obtained by linearizing of basic equations. On the other hand, in the nonlinear analysis, an energy-balance like equation involving Sagdeev's pseudo-potential is derived in order to investigate arbitrary amplitude IA solitons. The Mach number range is determi…
Modulational instability (MI) of ion-acoustic waves (IAWs) has been theoretically investigated in a plasma system which is composed of inertial warm adiabatic ions, isothermal positrons, and two temperature superthermal electrons. A nonlinear Schrödinger (NLS) equation is derived by using reductive perturbation method that governs the MI of the IAWs. The numerical analysis of the solution of NLS equation shows the existence of both stable (dark envelope solitons exist) and unstable (bright envelope solitons exist) regimes of IAWs. It is observed that the basic features (viz. stability of the w…
A double pair plasma system containing cold inertial positive and negative ions, and inertialess super-thermal electrons and positrons is considered. The standard nonlinear Schrödinger equation is derived by using the reductive perturbation method to investigate the nonlinear dynamics of the ion-acoustic waves (IAWs) as well as their modulation instability. It is observed that the ion-acoustic dark (bright) envelope solitons are formed for modulationally stable (unstable) plasma region, and that the presence of highly dense super-thermal electrons and positrons enhances (reduces) this unstable…
Nonlinear ion-acoustic waves are analyzed in a non-relativistic magnetized quantum plasma with arbitrary degeneracy of electrons. Quantum statistics is taken into account by means of the equation of state for ideal fermions at arbitrary temperature. Quantum diffraction is described by a modified Bohm potential consistent with finite temperature quantum kinetic theory in the long wavelength limit. The dispersion relation of the obliquely propagating electrostatic waves in magnetized quantum plasma with arbitrary degeneracy of electrons is obtained. Using the reductive perturbation method, the c…
A standard nonlinear Schrödinger equation has been established by using the reductive perturbation method to investigate the propagation of electrostatic dust-acoustic waves, and their modulational instability as well as the formation of localized electrostatic envelope solitons in an electron depleted unmagnetized dusty plasma system comprising opposite polarity dust grains and super-thermal positive ions. The relevant physical plasma parameters (viz., charge, mass, number density of positive and negative dust grains, and super-thermality of the positive ions, etc.) have rigorous impact to re…
The existence and the basic features of ion-acoustic (IA) envelope solitons in a self-gravitating degenerate quantum plasma system (SG-DQPS), containing inertial non-relativistically degenerate light and heavy ion species as well as inertialess non-relativistically degenerate positron and electron species, have been theoretically investigated by deriving the nonlinear Schrödinger (NLS) equation. The NLS equation, which governs the dynamics of the IA waves, has disclosed the modulationally stable and unstable regions for the IA waves. The unstable region allows to generate bright envelope solit…
Large amplitude kinetic Alfvénon (exact Alfvén soliton) matching condition is investigated in quasineutral electron-ion and electron-positron-ion plasmas immersed in a uniform magnetic field. Using the standard pseudopotential method, the magnetohydrodynamics (MHD) equations are exactly solved and a global allowed matching condition for propagation of kinetic solitary waves is derived. It is remarked that, depending on the plasma parameters, the kinetic solitons can be sub- or super-Alfvénic, in general. It is further revealed that, either upper or lower soliton speed-limit is independent of f…
Nonlinear propagation of purely stationary large amplitude electromagnetic (EM) solitary waves in a magnetized electron-positron (EP) plasma is studied using a fully relativistic two-fluid hydrodynamic model which accounts for physical regimes of both weakly relativistic $(P\ll nmc^2)$ and ultrarelativistic $(P\gg nmc^2)$ random thermal energies. Here, $P$ is the thermal pressure, $n$ the number density and $m$ the mass of a particle, and $c$ is the speed of light in vacuum. Previous theory in the literature [Phys. Plasmas \textbf{11}, 3078 (2004)] is advanced and generalized by the relativist…
Relativistic solitons are self-trapped, finite size, electromagnetic waves of relativistic intensity that propagate without diffraction spreading. They have been predicted theoretically within the relativistic fluid approximation, and have been observed in multi-dimensional particle in cell simulations of laser pulse interaction with the plasma. Solitons were observed in the laser irradiated plasmas with the proton imaging technique as well. This paper reviews many theoretical results on relativistic solitons in electron-ion plasmas.
The non-linear evolution of spin-electron acoustic, positron-acoustic, and spin-electron-positron acoustic waves is considered. It is demonstrated that weakly nonlinear dynamics of each wave leads to the soliton formation. Altogether, we report on existence of three different solitons. The spin-electron acoustic soliton known for electron-ion plasmas is described for electron-positron-ion plasmas for the first time. The existence of the spin-electron-positron acoustic soliton is reported for the first time. The positron-acoustic soliton and the spin-electron-positron acoustic soliton arise as …
A four component space plasma system (consisting of immobile positive ions, inertial cold positrons as well as hot electrons and positrons following Cairns' nonthermal distribution function is considered. The nonlinear propagation of the positron-acoustic (PA) waves, in which the inertia (restoring force) is provided by the cold positron species (nonthermal pressure of both hot electron and positron species) has been theoretically investigated by deriving the nonlinear Schrödinger (NLS) equation. It is found from the numerical analysis of this NLS equation that the space plasma system under co…
The basic features of nucleus-acoustic (NA) envelope bright and dark solitons, which exist in degenerate quantum plasmas, have been theoretically investigated by deriving the nonlinear Schrödinger (NLS) equation. The reductive perturbation method, which is valid for a small but finite amplitude limit, is employed. It is found that the bright envelope solitons are modulationally unstable, whereas the dark ones are stable. It is also observed that the fundamental properties (viz. Modulational instability (MI) growth rate, width and energy concentration of NA waves, etc.) of NA unstable bright en…
The excitation of precursor solitons ahead of a rapidly moving object in a fluid, a spectacular phenomenon in hydrodynamics that has often been observed ahead of moving ships, has surprisingly not been investigated in plasmas where the fluid model holds good for low frequency excitations such as ion acoustic waves. In this paper we report the first experimental observation of precursor solitons in a flowing dusty plasma. The nonlinear solitary dust acoustic waves (DAWs) are excited by a supersonic mass flow of the dust particles over an electrostatic potential hill. In a frame where the fluid …
A theoretical investigation of the modulational instability (MI) of dust-acoustic waves (DAWs) by deriving a nonlinear Schrödinger equation in an electron depleted opposite polarity dusty plasma system containing non-extensive positive ions has been presented. The conditions for MI of DAWs and formation of envelope solitons have been investigated. The sub-extensivity and super-extensivity of positive ions are seen to change the stable and unstable parametric regimes of DAWs. The addition of dust grains causes to change the width of both bright and dark envelope solitons. The findings of this s…
The excitation and evolution of Korteweg-de Vries (KdV) solitons in a dusty plasma medium are studied using Molecular Dynamics (MD) simulations. The dusty plasma medium is modelled as a collection of dust particles interacting through Yukawa potential, which takes into account dust charge screening due to the lighter electron and ion species. The collective response of such screened dust particles to an applied electric field impulse is studied here. An excitation of a perturbed positive density pulse propagating in one direction along with a train of negative perturbed rarefactive density osc…
The nature of fore-wake excitations created by a charged object moving in a magnetized plasma is investigated using particle-in-cell simulations. Our studies establish for the first time the existence of precursor magneto-sonic solitons traveling ahead of a moving charged object. The nature of these excitations and the conditions governing their existence are delineated. We also confirm earlier molecular dynamic and fluid simulation results related to electrostatic precursor solitons obtained in the absence of a magnetic field. The electromagnetic precursors could have interesting practical ap…
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 QULH (where ions are mobile). Quantum effects like Bohm potential, exchange correlation and Fermi pressure on the lower hybrid wave significantly reshaped the dispersion properties of lower hybrid waves. Later a set of nonlinear Zakharov equations have been de…
A generalized plasma model having warm ions, iso-thermal electrons, super-thermal electrons and positrons is considered to theoretically investigate the modulational instability (MI) of ion-acoustic waves (IAWs). A standard nonlinear Schrödinger equation is derived by applying reductive perturbation method to study the MI of IAWs. It is observed that the MI criteria of the IAWs are significantly modified by various plasma parameters. The present results should be useful in understanding the conditions for MI of IAWs which are relevant to both space and laboratory plasma system.
A phenomenological model using fluid theory is developed to show that the decay of two seemingly independent nonlinear structures namely the dust void and dust soliton strongly depends on the plasma ionization parameter in an unmagnetized complex plasma system. Numerical solution of model equations has shown that the evolution of dust voids and their subsequent decay in a time frame is intimately related with the ionization parameter. A similar result also holds good in case of dust solitons where stability of soliton is found to depend critically upon ionization parameter. Most importantly, i…
High-density low-temperature plasmas with degenerate species are considered in the limit of high Fermi velocities close to the speed of light. The small amplitude ion-acoustic solitons are studied in this regime. Presented analysis is based on the relativistic hydrodynamic model with the average reverse gamma factor evolution consists of the equations for evolution of the following functions the concentration, the velocity field, the average reverse relativistic gamma factor, and the flux of the reverse relativistic gamma factor, which are considered as main hydrodynamic variables. Justificati…
The dynamical behaviors of electromagnetic (EM) solitons formed due to nonlinear interaction of linearly polarized intense laser light and relativistic degenerate plasmas are studied. In the slow motion approximation of relativistic dynamics, the evolution of weakly nonlinear EM envelope is described by the generalized nonlinear Schr{ö}dinger (GNLS) equation with local and nonlocal nonlinearities. Using the Vakhitov-Kolokolov criteria, the stability of an EM soliton solution of the GNLS equation is studied. Different stable and unstable regions are demonstrated with the effects of soliton velo…
It is shown, using results of measurements of ion saturation current in the plasma edges of different magnetic fusion confinement devices (tokamaks and stellarators), that the plasma dynamics in the edges is dominated by distributed chaos with spontaneously broken translational symmetry at low magnetic field, and with spontaneously broken reflexional symmetry (by helical solitons) at high magnetic field.
It is shown that the pair plasmas with small temperature asymmetry can support existence of localized as well as de-localized optical vortex solitons. Coexistence of such solitons is possible due to peculiar form of saturating nonlinearity which has a focusing-defocusing nature -- for weak amplitudes being focusing becoming defocusing for higher amplitudes. It is shown that delocalized vortex soliton is stable in entire region of its existence while single- and multi-charged localized vortex solitons are unstable for low amplitudes and become stable for relativistic amplitudes.
The space-uniform amplitude envelope of the Ion Temperature Gradient driven turbulence is unstable to small perturbations and evolves to nonuniform, soliton-like modulated profiles. The induced poloidal asymmetry of the transport fluxes can generate spontaneous poloidal spin-up of the tokamak plasma.
We analyze the control of the propagation speed of three wave packets interacting in a medium with quadratic nonlinearity and dispersion. We found analytical expressions for mutually trapped pulses with a common velocity in the form of a three-parameter family of solutions of the three-wave resonant interaction. The stability of these novel parametric solitons is simply related to the value of their common group velocity.
Bending of solitons in two dimensional plane is presented in the presence of weak and slowly varying inhomogeneous ion density for the propagation of ion acoustic soliton in unmagnetized cold plasma with isothermal electrons. Using reductive perturbation technique, a modified Kadomtsev- Petviashvili equation is obtained with a chosen unperturbed ion density profile. Exact solution of the equation shows that the phase of the solitary wave gets modified by a function related to the unperturbed inhomogeneous ion density causing the soliton to bend in the two dimensional plane, whereas the amplitu…
We present a novel one-dimensional nonlinear evolution equation governing the dynamics short-wavelength longitudinal waves in a nonrelativistic fully degenerate quantum plasma using kinetic equation for the Wigner function. The linear dispersion of the equation has a form of "zero sound" $\sim k\exp (-k^{2})$, where $k$ is the wave number, and it strongly differs from previously known nonlinear evolution equations. We numerically find the corresponding soliton solutions and demonstrate that the collisions between three solitons turn out to be elastic resulting only in phase shifts.
Nonlinear propagation of electrostatic modes in ultrarelativistic dense elelectron-positron gravito-plasma at the polar cap region of pulsar magnetosphere is considered. A nonlinear Schrödinger equation is obtained from the reductive perturbation method which predicts the existence of Langmuir dark solitons. Relevance of the propagating dark solitons to the pulsar radio emission is discussed.
We study stable axially and spherically symmetric spatial solitons in plasma with diatomic ions. The stability of a soliton against the collapse is provided by the interaction of induced electric dipole moments of ions with rapidly oscillating electric field of a plasmoid. We derive the new cubic-quintic nonlinear Schrodinger equation which governs the soliton dynamics and numerically solve it. Then we discuss the possibility of implementation of such plasmoids in realistic atmospheric plasma. In particular, we suggest that spherically symmetric Langmuir solitons, described in the present work…
We derive a nonlinear equation governing dynamics of short-wavelength longitudinal waves in ultrarelativistic electron-positron-ion plasmas. In contrast to the recent work by Lashkin [Phys. Plasmas {\textbf{27}}, 102302 (2020)], where a similar equation was suggested in the framework of the Wigner function approach for a nonrelativistic electron-ion degenerate plasma, in our case which is based on the Vlasov kinetic equation all three species of particles (electrons, positrons and ions) should be present. The nonlinearity arises only in the presence of a population of ions. By numerical simula…
Acoustic solitons obtained through a reductive perturbation scheme are normally governed by a Korteweg-de Vries (KdV) equation. In multispecies plasmas at critical compositions the coefficient of the quadratic nonlinearity vanishes. Extending the analytic treatment then leads to a modified KdV (mKdV) equation, which is characterized by a cubic nonlinearity and is even in the electrostatic potential. The mKdV equation admits solitons having opposite electrostatic polarities, in contrast to KdV solitons which can only be of one polarity at a time. A Hirota formalism has been used to derive the t…
A set of fluid equations, taking into account the spin properties of the electrons and positrons in a magnetoplasma, are derived. The magnetohydrodynamic limit of the pair plasma is investigated. It is shown that the microscopic spin properties of the electrons and positrons can lead to interesting macroscopic and collective effects in strongly magnetized plasmas. In particular, it is found that new Alfvenic solitary structures, governed by a modified Korteweg-de Vries equation, are allowed in such plasmas. These solitary structures vanish if the quantum spin effects are neglected. Our results…
A number of possible pulsar radio emission mechanisms are based on streaming instabilities in relativistically hot electron-positron pair plasmas. At saturation the unstable waves can form, in principle, stable solitary waves which could emit the observed intense radio signals. We searched for the proper plasma parameters which would lead to the formation of solitons, investigated their properties and dynamics as well as the resulting oscillations of electrons and positrons possibly leading to radio wave emission. We utilized a one-dimensional version of the relativistic Particle-in-Cell code …
Using the extended Poincaré-Lighthill-Kuo (PLK) reductive perturbation method to study the small-amplitude ion acoustic solitary wave (IASW) dynamics (propagation and interaction), it is shown that in Thomas-Fermi magneto-plasma consisting of inertial-less degenerate electrons and positrons and isothermal ions, distinctive features emerge when the ultra-relativistic degeneracy pressure applies to electrons and positrons. Calculations show that ion-acoustic solitary waves may interact differently in such plasmas under ultra-relativistic degeneracy pressure.
The nonlinear evolution of the quantum two-stream instability in a plasma with counter-streaming electron beams is studied. It is shown that in the long-wave limit the nonlinear stage of the instability can be described by the elliptic nonlinear string equation. We present two types of the nonlinear solutions. The first one is an unstable nonlinear mode that is continuously related with the growing linear solution and the second one is a pulsating soliton. We show that both of these solutions blow up in a finite time.
We investigate the existence conditions and propagation properties of electron-acoustic solitary waves in a plasma consisting of an electron beam fluid, a cold electron fluid, and a hot suprathermal electron component modeled by a $κ$-distribution function. The Sagdeev pseudopotential method was used to investigate the occurrence of stationary-profile solitary waves. We have determined how the soliton characteristics depend on the electron beam parameters. It is found that the existence domain for solitons becomes narrower with an increase in the suprathermality of hot electrons, increasing th…
Theoretical and numerical studies are presented of the amplitude modulation of electron-acoustic waves (EAWs) propagating in space plasmas whose constituents are inertial cold electrons, Boltzmann distributed hot electrons and stationary ions. Perturbations oblique to the carrier EAW propagation direction have been considered. The stability analysis, based on a nonlinear Schroedinger equation (NLSE), reveals that the EAW may become unstable; the stability criteria depend on the angle $θ$ between the modulation and propagation directions. Different types of localized EA excitations are shown to…
The supercritical composition of a plasma model with cold positive ions in the presence of a two-temperature electron population is investigated, initially by a reductive perturbation approach, under the combined requirements that there be neither quadratic nor cubic nonlinearities in the evolution equation. This leads to a unique choice for the set of compositional parameters and a modified Korteweg-de Vries equation (mKdV) with a quartic nonlinear term. The conclusions about its one-soliton solution and integrability will also be valid for more complicated plasma compositions. Only three pol…
