Waves In Magnetized Plasma Research Articles

3D electron‐acoustic solitary waves introduced by phase space electron vortices in magnetized space plasmas

We derive a multi‐dimensional nonlinear equation for electron‐acoustic waves in magnetized plasmas composed of stationary ions, magnetized cold electrons with a significant fraction of electron beams, and magnetized hot electrons which have a non‐isothermal vortex‐like distribution. We find three‐dimensional (3D) electron‐acoustic solitary waves which have a stronger nonlinearity (in comparison with that associated with the traditional harmonic generation) due to the trapping of hot electrons in the localized electron‐acoustic wave potential. The relevance of our investigation to nonlinear structures (e.g., the bipolar parallel electric fields) in the Earth's magnetosphere is discussed.

Linear and nonlinear properties of Rao-dust-Alfvén waves in magnetized plasmas

The linear and nonlinear properties of the Rao-dust-magnetohydrodynamic (R-D-MHD) waves in a dusty magnetoplasma are studied. By employing the inertialess electron equation of motion, inertial ion equation of motion, Ampère’s law, Faraday’s law, and the continuity equation in a plasma with immobile charged dust grains, the linear and nonlinear propagation of two-dimensional R-D-MHD waves are investigated. In the linear regime, the existence of immobile dust grains produces the Rao cutoff frequency, which is proportional to the dust charge density and the ion gyrofrequency. On the other hand, the dynamics of amplitude modulated R-D-MHD waves is governed by the cubic nonlinear Schrödinger equation. The latter has been derived by using the reductive perturbation technique and the two-timescale analysis which accounts for the harmonic generation nonlinearity in plasmas. The stability of the modulated wave envelope against non-resonant perturbations is studied. Finally, the possibility of localized envelope excitations is discussed.

Perfectly matched layers for radio wave propagation in inhomogeneous magnetized plasmas

We present 1D and 2D numerical models of the propagation of high-frequency (HF) radio waves in inhomogeneous magnetized plasmas. The simulations allow one to describe the process of linear conversi...

Waves propagating along a density gradient in a dusty plasma

The waves propagating in the direction of a density gradient in a dusty plasma are analyzed. The analysis includes the recently predicted electrostatic dust Rossby mode that can develop in a rotating dusty plasma with charged grains, as well as waves in magnetized plasmas, and dust acoustic waves. The spatial behavior of the mode amplitude is determined for a few realistic plasma density profiles.

EXACT EXPLICIT SOLUTIONS OF THE NONLINEAR SCHRÖDINGER EQUATION COUPLED TO THE BOUSSINESQ EQUATION

A system comprised of the nonlinear Schrödinger equation coupled to the Boussinesq equation (S-B equations) which dealing with the stationary propagation of coupled non-linear upper-hybrid and magnetosonic waves in magnetized plasma is proposed. To examine its solitary wave solutions, a reduced set of ordinary differential equations are considered by a simple traveling wave transformation. It is then shown that several new solutions (either functional or parametrical) can be obtained systematically, in addition to rederiving all known ones by means of our simple and direct algebra method with the help of the computer algebra system Maple.

A Gordeyev integral for electrostatic waves in a magnetized plasma with a kappa velocity distribution

A Gordeyev-type integral for the investigation of electrostatic waves in magnetized plasma having a kappa or generalized Lorentzian velocity distribution is derived. The integral readily reduces, in the unmagnetized and parallel propagation limits, to simple expressions involving the Zκ function. For propagation perpendicular to the magnetic field, it is shown that the Gordeyev integral can be written in closed form as a sum of two generalized hypergeometric functions, which permits easy analysis of the dispersion relation for electrostatic waves. Employing the same analytical techniques used for the kappa distribution, it is further shown that the well-known Gordeyev integral for a Maxwellian distribution can be written very concisely as a generalized hypergeometric function in the limit of perpendicular propagation. This expression, in addition to its mathematical conciseness, has other advantages over the traditional sum over modified Bessel functions form. Examples of the utility of these generalized hypergeometric series, especially how they simplify analyses of electrostatic waves propagating perpendicular to the magnetic field, are given. The new expression for the Gordeyev integral for perpendicular propagation is solved numerically to obtain the dispersion relations for the electrostatic Bernstein modes in a plasma with a kappa distribution.

Taming Drift Wave Turbulence

Drift waves in magnetized plasmas often occur in a turbulent form and are often considered as being responsible for anomalous cross-field particle transport. It is thus very appealing to achieve active control of the drift wave dynamics. A control scheme acting both in space and in time is developed to synchronize drift wave turbulence. It consists of an arrangement of eight electrodes (octupole exciter) in flush-mounted geometry in the edge region of the magnetized plasma column. The electrodes of the octupole exciter are driven by sinusoidal signals. Between each two neighbouring electrodes, the phase shift of the exciter signal is kept fixed. It is demonstrated experimentally that the exciter signals have strong influence on the different drift wave states, i.e. the turbulent states can be synchronized to a single preselected drift wave mode. The efficiency of the spatiotemporal synchronization is sensitively dependent on both driver frequency and phase shift.

Taming Drift Wave Turbulence

Drift waves in magnetized plasmas often occur in a turbulent form and are often considered as being responsible for anomalous cross-field particle transport. It is thus very appealing to achieve active control of the drift wave dynamics. A control scheme acting both in space and in time is developed to synchronize drift wave turbulence. It consists of an arrangement of eight electrodes (octupole exciter) in flush-mounted geometry in the edge region of the magnetized plasma column. The electrodes of the octupole exciter are driven by sinusoidal signals. Between each two neighbouring electrodes, the phase shift of the exciter signal is kept fixed. It is demonstrated experimentally that the exciter signals have strong influence on the different drift wave states, i.e. the turbulent states can be synchronized to a single preselected drift wave mode. The efficiency of the spatiotemporal synchronization is sensitively dependent on both driver frequency and phase shift.

Theory of stimulated scattering of large-amplitude waves

Comprehensive comments on the theory of stimulated scattering instabilities of high-frequency electromagnetic waves in magnetized plasmas are presented. It is shown that our general dispersion relations are appropriate for deducing valuable information regarding the growth rates of scattering instabilities and the long-term evolution of modulationally unstable waves in space and laboratory plasmas as well as in astrophysical settings.

Hydrodynamical Description of a Photon Gas in Magnetized Plasmas

The propagation for relativistically intense and broad spectrum EM waves in magnetized plasmas is considered. A general kinetic equation for the photon spectral function is derived and used to obtain a set of hydrodynamical equations for the particular case of helicon waves. Numerical calculations for the 1-D set of equations with a Gaussian distribution function at t = 0 shows that the profile of density changes its shape in the course of time and forms a discontinuity.

Weakly nonlinear high frequency waves in magnetized plasmas

The evolution of nonlinear electron plasma waves in weakly magnetized plasmas is studied for conditions where the principal waves propagate along the magnetic field lines. The analysis is based on an electrostatic fluid model for the waves. Numerical results using a spectral method with periodic boundary conditions demonstrate “quasi-collapsing” solutions for localized initial conditions with sufficiently high amplitude. The possibility of acceleration of electrons by the high-frequency waves is discussed. It is demonstrated that electrons are likely to gain energy in parts of the nonlinear wavepacket and to loose all, or most of, this energy again in other parts.

Nonlinear coupling between intense neutrino fluxes and dense magnetoplasmas

The nonlinear coupling between intense neutrino fluxes and a dense magnetized plasma is considered. It is shown that the coupling is governed by a pair of equations consisting of a nonlinear Klein-Gordon equation for the neutrinos and an equation governing a variety of magnetized plasma waves that are driven by the neutrino energy density. The system of equations is then used to investigate parametric instabilities, envelope solitons, as well as wake field generation. The relevance of our investigation to supernova explosions in pointed out.

Nonlinear Alfvén waves in magnetized plasmas with heavy impurities or dust.

Nonlinear electromagnetic wave propagation in a magnetized plasma with heavy impurities, in particular, dust grains, at frequencies below and of the order of the ion-cyclotron frequency is considered. The presence of immobile dust grains leads to a considerable change of the dispersion characteristics for Alfv\'en waves propagating along the uniform magnetic field, especially for small wave numbers when two modes with a relatively large frequency gap appear. We discuss the consequences of this dispersion for the nonlinear properties of the waves.

Nonlinear dynamics of low-frequency drift waves

The nonlinear behaviour of unstable drift waves in magnetized plasmas is analysed analytically. Most attention is paid to low-frequency waves created in electron density and temperature gradients of opposite sign. This situation is typically encountered in radiofrequency-produced discharges. The model developed explains nonlinear features such as mode competition, amplitude saturation and magnetic field hysteresis, which are observed experimentally.

Emission of electromagnetic waves in magnetized plasma in the presence of field aligned currents: A model for occurrence of circular polarizations in the pulsar radiations

The growth rate of electromagnetic waves, in the whistler mode frequency range, in the presence of field aligned currents is calculated. A model for the occurrence of circular polarizations in pulses of pulsars is presented.

Excitation of plasma waves by electromagnetic waves in magnetized plasmas

Three-dimensional equations for the plasma wake fields in the presence of a single frequency, intense circularly polarized electromagnetic (CPEM) wave in a two-component magnetoplasma are derived. For a given CPEM envelope, the axial electric fields of plasma waves are obtained for a one-dimensional model problem in which all the waves are aligned along the magnetic-field lines. It is found that the presence of an external magnetic field can significantly enhance the strength of the plasma wake fields when the right-hand CPEM wave is used for the excitation purposes.

A new class of exact solutions for coupled scalar field equations

The authors report a class of exact solutions valid in new regimes of parameter values for a generic system of nonlinear coupled scalar field equations which is the stationary reduction of the Schrodinger-Boussinesq (or Korteweg-de Vries) system, and which extends the Henon-Heiles system to Hamiltonians with indefinite kinetic energy. The results are applied to co-propagating coupled nonlinear waves in magnetized plasmas.

Induced Scattering Due to Nonlinear Landau and Cyclotron Damping of Electromagnetic and Electrostatic Waves in a Magnetized Plasma

General expressions of the matrix elements for nonlinear wave-particle scattering (nonlinear Landau and cyclotron damping) of electromagnetic and electrostatic waves in a homogeneous magnetized plasma are derived from the Vlasov-Maxwell equations. The kinetic wave equations obtained for electromagnetic waves are expressed by four-order tensors in the rotating and cartesian coordinates. No restrictions are imposed on the propagation angle to a uniform magnetic field, the Larmor radius, the frequencies, or the wave numbers. By electrostatic approximation of the dielectric tensor and the matrix elements the kinetic wave equations can be applied to the case in which two scattering waves are electrostatic or they are partially electrostatic. Further, the matrix elements in the limit of parallel or perpendicular propagation to the magnetic field are given.

Filamentation instability of electromagnetic waves in magnetized plasmas

The filamentation instability of electromagnetic electron and ion-cyclotron waves is investigated by including the combined effect of relativistic electron mass variation as well as static density and field-aligned magnetic field perturbations that are created by the radiation pressure. Analytical expressions for the critical power at which the instability starts are presented. The relevance of this investigation to radio-frequency wave heating of fusion plasmas is pointed out.

Three-wave coupling coefficients for magnetized plasmas with pressure anisotropy

In order to find the equations for the nonlinear energy exchange between low-frequency waves in magnetized plasmas in the presence of pressure anisotropy, we start from the Chew–Goldberger–Low equations, the isothermal MHD equations, as well as a new hybrid system of equations. The coupling coefficients describing the interaction between two Alfvén waves and one magnetosonic wave as well as the interaction between two magnetosonic waves and one Alfvén wave are deduced.