Dynamics Of Ion-acoustic Waves Research Articles

Mechanisms of Fundamental Electromagnetic Wave Radiation in the Solar Wind

Large-scale and long-term two-dimensional particle-in-cell simulations performed for parameters relevant to type III solar radio bursts have provided new results on the generation mechanisms of fundamental electromagnetic waves radiated at the plasma frequency ω p . The paper first considers the nonlinear wave interaction process of electromagnetic decay (EMD) in a homogeneous solar wind plasma with an electron-to-ion temperature ratio T e /T i > 1. The dynamics of ion-acoustic waves (dispersion, spectra, growth/damping) is studied, and signatures confirming the three-wave interactions (cross-bicoherence, correlations between waves’ phases and between waves' growths, resonance conditions) are provided. The decisive role played in EMD by the backscattered Langmuir waves coming from the electrostatic decay (ESD) is demonstrated. EMD can be triggered by ion acoustic waves coming from the two cascades of the faster and more intense ESD. The same study is then performed in a solar wind plasma with random density fluctuations. In this case, EMD is not suppressed but develops only within plasma regions of reduced or quasi-uniform density. It coexists with linear mode conversion (LMC) of Langmuir waves into electromagnetic radiation, which is the fastest and most prominent process, as well as with ESD. LMC can lead to enhanced occurrence of EMD in the early stage. Moreover, the impact of T e /T i on electromagnetic energy growth and saturation is shown to be rather weak. Ion-acoustic waves are heavily damped at T e ∼ T i , so that EMD is overcome by nonlinear induced scattering on thermal ions. In actual solar wind plasmas, EMD should be more easily observed in plasma regions weakly perturbed by the background density turbulence and where ion temperature is decreased.

Dynamics of ion-acoustic waves in multi-species quantum plasmas with arbitrary degeneracy

Dynamics of ion-acoustic waves in multi-species quantum plasmas with arbitrary degeneracy

Numerical analysis of twisted ion-acoustic waves

Twisted ion-acoustic waves with finite orbital angular momentum (OAM) states are numerically investigated in a plasma containing electrons, positrons and dynamical ions. For this purpose, the well-known Vlasov–Poisson equations are solved together under the paraxial approximation. The perturbed quantities are assumed to follow the Laguerre–Gaussian type solutions and a generalized plasma response function for finite OAM states is derived. The generalized response function is numerically analyzed to investigate dispersion characteristics of the twisted ion-acoustic waves. Consequently, a computer code is developed which is based on the very famous numerical technique known as the Newton–Raphson method. The dependence of the (real) wave oscillation frequency and damping rate involving the twisted ion-acoustic waves is highlighted with different plasma parameters. It is found that the dynamics of ion-acoustic waves are strongly influenced by the twist parameter owing to OAM states. The results obtained in the present study are useful in the understanding of the particle transport and trapping phenomena.

Ion-acoustic wave dynamics and sensitivity study in a magnetized Auroral phase plasma

The dynamic behavior of ion-acoustic waves (IAWs) inside a magnetized auroral zone plasma including ions as well as two-temperature electrons is investigated. The Kadomtsev–Petviashvili (KP) and modified KP (mKP) equations are provided using the reductive perturbation method (RPT). In fluid dynamics, plasma physics, and electrodynamics, mKP equation can be utilized to characterize wave phenomena. It increases our interest due to its significant physical and mechanical value. The new extended direct algebraic approach is used to compute several traveling wave patterns for the nonlinear mKP equation. It is a simple, concise and general method in symbolic computations for solitary wave solutions for nonlinear problems. It yields dark solitary solutions, the community for semi-dark soliton results, dark singular soliton effects, kink soliton results, and soliton consequences encompassing trigonometric function, mixture hyperbolic function, as well as rational functions. Some arbitrarily chosen solutions are displayed visually for physical understanding. Moreover, the sensitivity of the perturbed dynamical structure equivalent to the mKP equation has been explored. Furthermore, the effect of IAWs spectral index on the parameters of the solitary-wave solutions and the sensitivity of the perturbed dynamical system of mKP equations is investigated in detail.

Three dimensional wave group dynamics of ion acoustic waves in electron–positron–ion plasmas in the presence of an external uniform magnetic field

Three dimensional (3D) wave group dynamics of ion acoustic wave is studied in electron–positron–ion (EPI) plasmas incorporating the effects of an external uniform magnetic field through the Laedke–Spatschek equation. In the presence of self-interaction (self-focusing effect), the wave group dynamics is shown to be governed by a (3 + 1) nonlinear Schrödinger equation. The derived nonlinear equations are solved analytically and the solutions predict a wide class of nonlinear structures in EPI plasma in the presence of magnetic field. The boundaries of stable and unstable solutions are also specified in parametric space. The results are expected to provide deeper insights into the ionic processes occurring in both astrophysical and laboratory plasmas.

Dynamics of ion-acoustic waves in nonrelativistic magnetized multi-ion quantum plasma: the role of trapped electrons

The presented work provides a new perspective of quantum nonlinear propagation of ion-acoustic (IA) waves in a magnetized collisionless and dissipative multi-ion plasma system, composed of cold positive and negative charged nonrelativistic ions, negatively charged immobile heavy ions and trapped electrons; all existed in a quantizing magnetic field. We address the reductive perturbation method to derive the Korteweg-de Vries- Burgers (KdV-Burgers) and modified KdV-Burgers equations. The bifurcation theory of planar dynamical systems is applied to investigate the existence of the solitary wave and the periodic traveling wave solutions of the resulting mKdV-Burgers equation. Accordingly, the phase portrait topology is illustrated for this equation. To study the nonlinear waves in case of mKdV- Burgers, we obtain some interesting physical solutions for mKdV- Burgers. These solutions are in the form of soliton, a combination between the shock and the soliton, and finally monotonic and oscillatory shock waves. Only rarefactive IA waves are obtained for the slow mode of phase velocity. It is found that the IA solitons, IA shocks are affected by the plasma system parameters. The presented theoretical research can be successfully implemented to understanding the solitary and shocks structures in dense magnetized quantum plasmas such as those existing in white dwarfs and in the intense-laser plasma interactions.

Dynamics of ion-acoustic waves in Thomas-Fermi plasmas with source term

Dynamics of ion acoustic waves are studied in Thomas-Fermi plasmas with source term consisting of electrons, positrons and positive ions, where electrons and positrons follow zero-temperature Fermi-gas statistics, but ions behave as classical fluid. Using RPT (reductive perturbation technique) the forced KdV and modified KdV equations are obtained. Employing the concept of planar dynamical systems, periodic, quasiperiodic and chaotic features of ion-acoustic waves are studied in Thomas-Fermi plasmas with space debris depending on positron concentration (α), speed (vd) of the space debris and strength (f0) of source perturbation. The results of this work may have relevance in the Thomas-Fermi plasma environments with space debris.

Dissipative ion acoustic solitary waves in collisional, magneto‐rotating, non‐thermal electron–positron–ion plasma

The linear and non‐linear dynamics of ion acoustic waves are investigated in three‐component magnetized plasma consisting of cold inertial ions and non‐thermal electrons and positrons. The non‐thermal components are modelled by the hybrid distribution, representing the combination of two (kappa and Cairn's) non‐thermal distributions. The relevant processes, including the slow rotation of plasma along the magnetic field axis and collision between ions and neutrals, are taken into consideration. It is shown that the non‐linear dynamics of the considered system are governed by the Zakharov–Kuznetsov equation in modified form. In the general dissipation regime, the effects of the two non‐thermal distributions on the solitary waves are compared. The effects of other plasma parameters, such as collisional and rotational frequency, are also discussed in detail.

Multidimensional nonlinear ion-acoustic waves in a plasma in view of relativistic effects

The structure and dynamics of ion-acoustic waves in an unmagnetized plasma, including the case of weakly relativistic collisional plasma (when it is necessary to take into account the high energy particle flows which are observed in the magnetospheric plasma), are studied analytically and numerically on the basis of a model of the Kadomtsev-Petviashvili (KP) equation. It is shown that, if the velocity of plasma particles approaches the speed of light, the relativistic effects start to strongly influence on the wave characteristics, such as its phase velocity, amplitude, and characteristic wavelength, with the propagation of the twodimensional solitary ion-acoustic wave. The results can be used in the study of nonlinear wave processes in the magnetosphere and in laser and astrophysical plasma.

Numerical Simulation to Study the Nonlinear Interaction Between Slow Magnetosonic Wave and Ion Acoustic Wave in Solar Wind Plasmas

We have studied the nonlinear interaction between slow magnetosonic waves (SMSW) and ion acoustic waves (IAW) by numerical simulation. Our model assumes that the SMSW as a pump wave and that its density perturbation is due to IAW. If the ponderomotive force components of SMSW are included in the dynamics of IAW, the governing equations for IAW and SMSW are formulated as coupled nonlinear equations. We carried out numerical simulations of these coupled equations and evaluated the localized filamentary structures and the magnetic power spectrum for an angle of propagation θ=70∘. These intense localized structures and power spectra satisfy the scaling law, k−s (2≤s≤4), in the dispersive range, which may contribute to the acceleration of particles in the solar wind.

Fully kinetic simulation of ion acoustic and dust-ion acoustic waves

A series of numerical simulations is presented, based on a recurrence-free Vlasov kinetic model using kinetic phase point trajectories. All plasma components are modeled kinetically via a Vlasov evolution equation, then coupled through Poisson’s equation. The dynamics of ion acoustic waves in an electron-ion and in a dusty (electron-ion-dust) plasma configuration are investigated, focusing on wave decay due to Landau damping and, in particular, on the parametric dependence of the damping rate on the dust concentration and on the electron-to-ion temperature ratio. In the absence of dust, the occurrence of damping was observed, as expected, and its dependence to the relative magnitude of the electron vs ion temperature(s) was investigated. When present, the dust component influences the charge balance, enabling dust-ion acoustic waves to survive Landau damping even in the extreme regime where Te ≃ Ti. The Landau damping rate is shown to be minimized for a strong dust concentration or/and for a high value of the electron-to-ion temperature ratio. Our results confirm earlier theoretical considerations and contribute to the interpretation of experimental observations of dust-ion acoustic wave characteristics.

Dynamics of fundamental electromagnetic emission via beam-driven Langmuir waves

The nonlinear process of electromagnetic Langmuir decay, which leads to radio emission near the plasma frequency, is studied for situations in which Langmuir waves are directly driven by an electron beam and indirectly generated via electrostatic Langmuir decays. The electromagnetic Langmuir decay is stimulated by the presence of ion-acoustic waves. An approximate method is devised for studying this emission process with axial symmetry (along the direction of beam propagation) in three spatial dimensions, based upon the Langmuir and ion-acoustic wave dynamics in one spatial dimension. Numerical studies of the fundamental electromagnetic emission starting from electron dynamics are then carried out via quasilinear theory, and the results are explored for illustrative parameters. The evolution of the fundamental transverse waves shows the combined effects of local emission and propagation away from the source. At a given location, the emission rate shows a series of peaks associated with successive electromagnetic decays of the Langmuir waves, which are either driven by the beam or produced by successive electrostatic decays. The emission rate for a given electromagnetic decay decreases with time, following an initial increase. In addition, the emission rate for a specific electromagnetic decay shows approximate dipolar form, consistent with previous analytical work. Consequently, the fundamental transverse waves emitted locally propagate approximately symmetrically in both the forward and the backward directions. Variation of the background electron to ion temperature ratio, beam injection parameters, and angular widths of the Langmuir and ion-acoustic spectra are found to affect the emission rate and, hence, the fundamental transverse wave levels. Furthermore detailed studies show that the wave numbers of the maximum emission rates are also in good agreement with an approximate prediction for simple model Langmuir and ion-acoustic spectra.

Second harmonic electromagnetic emission via beam-driven Langmuir waves

The linked nonlinear processes of electrostatic Langmuir decay and electromagnetic emission at the second harmonic plasma frequency are studied for situations in which Langmuir waves are driven by an electron beam. An approximate method for studying wave decay and emission in three spatial dimensions is developed, based on the Langmuir and ion-acoustic wave dynamics in one spatial dimension. The numerical solutions of quasilinear equations to study electromagnetic emission starting from the electron dynamics are carried out. The numerical results are explored for illustrative parameters. The evolution of the transverse waves shows the combined effects of local emission and propagation away from the source. At a given location, the emission rate shows a series of peaks associated with coalescences of Langmuir waves driven by the beam and those produced by successive decays. The emission rate for a given coalescence decreases with time, following an initial increase. The effects of transverse wave propagation are illustrated by the presence of transverse waves both in regions upstream of the beam injection site due to backward propagation, and in regions downstream (e.g., where Langmuir waves are at thermal levels prior to the arrival of the beam) owing to forward propagation. Variation of the background electron to ion temperature ratio, beam injection parameters, and angular widths of the Langmuir spectra are found to affect the emission rate and the transverse wave levels. Furthermore, detailed studies show that the wave numbers of the maximum emission rates are in semiquantitative agreement with a previous theoretical prediction for simple model Langmuir spectra.