Coupled gravitational and electromagnetic waves in arbitrary space-times with magnetized plasmas and dust,I

We derive constraint-free, coupled wave equations for the propagation of coupled electromagnetic and gravitational waves traveling through a time-dependent inhomogeneous medium. The medium consists of an arbitrary gravitational field, dust, a cold two-fluid plasma, and an arbitrary magnetic field. In this first of two papers we apply a two-timing ansatz to the constraint-free system of wave equations. In the second paper, dispersion relation and transport equations are found by means of a WKB analysis.     

A Gyrokinetic simulation model for low frequency electromagnetic fluctuations in magnetized plasmas

We present a new model for simulating the electromagnetic fluctuations with frequencies much lower than the ion cyclotron frequency in plasmas confined in general magnetic configurations.This novel model(termed as GK-E&B)employs nonlinear gyrokinetic equations formulated in terms of electromagnetic fields along with momentum balance equations for solving fields.It,thus,not only includes kinetic effects,such as wave-particle interaction and microscopic(ion Larmor radius scale)physics;but also is computationally more efficient than the conventional formulation described in terms of potentials.As a benchmark,we perform linear as well as nonlinear simulations of the kinetic Alfvén wave;demonstrating physics in agreement with the analytical theories.     

Exponential frequency spectrum in magnetized plasmas

Measurements of a magnetized plasma with a controlled electron temperature gradient show the development of a broadband spectrum of density and temperature fluctuations having an exponential frequency dependence at frequencies below the ion cyclotron frequency. The origin of the exponential frequency behavior is traced to temporal pulses of Lorentzian shape. Similar exponential frequency spectra are also found in limiter-edge plasma turbulence associated with blob transport. This finding suggests a universal feature of magnetized plasma turbulence leading to nondiffusive, cross-field transport, namely, the presence of Lorentzian shaped pulses.     

Spectra of high-frequency waves in hot magnetized plasmas

On the basis of numerical solution of the dispersion equation, we obtain the spectra of weakly damped high-frequency waves in a hot magnetized plasma for the case where the electron cyclotron frequency ω_He is below the plasma frequency ω_pe. It is shown that the longitudinal wave propagating at an angle to the magnetic field evolves into the slow extraordinary wave for the refractive index n ≤ 1. For n ≫ 1, the longitudinal-wave frequency increases with the refractive index, and the wave evolves into the wave with anomalous dispersion if the angle θ between the wave vector and the magnetic field is close to 90°. In the same range of θ angles, Bernstein modes appear in the spectrum of plasma eigenmode oscillations. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 3, pp. 258–266, March 2006.     

Ultra-low-frequency electrostatic and electromagnetic modes in self-gravitating magnetized dusty plasmas

A theoretical investigation has been made of ultra-low-frequency dust-electrostatic and dust-electromagnetic modes, propagating perpendicular to the external magnetic field, in a self-gravitating, warm, magnetized, two fluid dusty plasma system. It has been shown that the effects of self-gravitational field and dust thermal pressure significantly modify the dispersion properties of these ultra-low-frequency dust-modes. It is also found that under certain conditions, the self-gravitational effect can destabilize these ultra-low-frequency dust-electrostatic and dust-electromagnetic modes. However, the effects of the external magnetic field and dust and ion thermal pressures are found to play stabilizing role, i.e., these effects make these modes stable and counter the gravitational condensation of the dust grains. The implications of these results to some space and astrophysical dusty plasma systems, especially, to planetary ring-systems and cometary tails, are briefly mentioned. Received 16 December 1999     

Large-amplitude electromagnetic waves in relativistic plasmas

The propagation of linearly polarized large-amplitude electromagnetic waves in relativistic plasmas is studied in the framework of the Akhiezer-Polovin-model. Different forms of the basic equations are reviewed and important solutions are presented for small and critical plasma densities. The well-known periodic solutions are generalized to quasiperiodic solutions taking account of additional electrostatic oscillations.     

Structure of the electromagnetic fields of loop radiators in magnetized plasmas over the whistler frequency range

The role of different sections of the spatial spectrum of whistler waves excited by a loop antenna in the formation of an electromagnetic field structure is investigated experimentally and theoretically. Primary attention is given to the intermediate range of distances between the source and the observation point.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 2, pp. 192–202, February, 1996.T. M. Zaboronkova, A. V. Kostrov, A. I. Smirnov, and A. A. Shaikin are grateful to The Russian Foundation for Fundamental Research (Grant No.94-02-05447a) and the George Soros International Foundation (Grant No. NOP 300) for financial support. A. V. Kudrin is grateful to the Russian Fund for Fundamental Research (Grant No. 96-02-18666) for financial support.     

Manipulating electromagnetic waves with metamaterials: Concept and microwave realizations

Our recent efforts in manipulating electromagnetic （EM） waves using metamaterials （MTMs） are reviewed with em- phasis on 1） manipulating wave polarization and transporting properties using homogeneous MTMs, 2） manipulating surface-wave properties using plasmonic MTMs, and 3） bridging propagating and surface waves using inhomogeneous meta-surfaces. For all these topics, we first illustrate the physical concepts and then present several typical practical real- izations and applications in the microwave regime.     

Self-reflection of intense electromagnetic waves in plasmas

A uniform electromagnetic wave of high power density, propagating in a collisional plasma gives rise to a modification in temperature-dependent collision frequency and in turn induces a gradient in the complex refractive index of the medium. A WKB solution of the problem predicts a backward propagating wave on account of the self-induced inhomogeneity. The amplitude of the backward (i.e. reflected) wave increases with increasing power density of the wave. This is a volume nonlinear effect and is appreciable for usually employed power densities.     

Shock waves in magnetized plasmas with superthermal trapped electrons.

Formation of ion-acoustic shock waves (IAShWs) and their propagation nature in a magnetized plasma in the presence of superthermal trapped electrons are investigated for the first time via the fluid dynamical approach. A magnetized plasma system, comprising of inertial ions and non-inertial electrons following $\kappa$-superthermal trapped distribution, is considered to examine the basic features (amplitude, width, phase speed, etc.) of IAShWs in such a plasma. A diffusion effect (due to the ion kinematic viscosity) is taken into account. The reductive perturbation technique is adopted to derive the modified Korteweg de-Vries Burgers’ (mKdVB) equation and the solution of mKdVB equation (derived by adopting the tangent hyperbolic method) is used to investigate the dynamical and structural characteristics (speed, amplitude, width, etc.) of IAShWs. The influence of relevant plasma (configuration) parameters (e.g., the superthermality index $\kappa ,$ concentration of trapped electrons, external magnetic field, and obliquity angle, etc.) on the nature of IAShWs is examined. The applications of the results in space and laboratory plasma environments, where nonthermal trapped electrons are available, are briefly discussed.     

磁化分层等离子体中电磁波传播特性研究

采用混合矩阵法,分析了磁化分层等离子鞘套对斜入射电磁波传播特性的影响,分别计算了不同入射角以及外加磁场下电磁波透射系数和极化特性的变化。以GPS导航信号右旋圆极化波(RCP)为例,研究了磁场、电子密度对电磁波右旋圆极化特性的影响。结果表明,外加磁场能够使右旋圆极化波在等离子体中的阻带向高频方向移动,此外,外加磁场能在一定程度上改善斜入射是圆极化波的极化特性,有利于GPS信号接收。     

Ion acoustic solitary waves with adiabatic ions in magnetized electron-positron-ion plasmas

Linear and nonlinear ion acoustic waves in the presence of adiabatically heated ions in magnetized electron-positron-ion plasmas are studied. The Sagdeev potential approach is employed to obtain the energy integral equation in such a mulitcomponent plasma using fluid theory. It is found that electron density humps are formed in the subsonic region in magnetized electron-positron-ion plasmas. The amplitude of electron density hump is decreased with the increase of hot ion temperature in electron-positron-ion plasmas. However, the increase in positron concentration and obliqueness of the wave increases the amplitude of nonlinear structure. The increase in positron concentration also reduces the width of the nonlinear structure in a magnetized multicomponent plasma. The numerical solutions in the form of solitary pulses are also presented for different plasma cases. The results may be applicable to astrophysical plasma situations, where magnetized electron-positron-ion plasma with hot ions can exist.     

Propagation properties of dust-electron-acoustic waves in weakly magnetized dusty nonthermal plasmas

The linear and nonlinear properties of dust-electron acoustic waves (DEAWs) propagating in magnetized, collisionless, dusty plasma system containing inertial cold electrons, Maxwellian hot electrons, nonthermal ions, and arbitrarily (positively or negatively) charged stationary dust are investigated. The reductive perturbation technique is employed to reduce the basic set of fluid equations to the modified Korteweg-de Vries equation or Ostrovsky's equation, which governs the dynamics of small amplitude DEAWs in a weakly magnetized dusty nonthermal plasma. The approximate analytical as well as numerical solutions reveal that the basic characteristics of DEA nonlinear structures are found to be significantly modified by the key plasma configuration parameters. It is found that the leading compressive or rarefactive solitary wave structure separates from a trailing wave packet during a considerable time under the influence of magnetic field-induced Lorentz force.     

Double passage of electromagnetic waves through magnetized plasma: approximation of independent normal waves

Polarization properties of electromagnetic waves, double-passed through magnetized plasma, are studied. Analyses are performed in the case of non-interacting normal modes, propagating in homogeneous and weakly inhomogeneous plasmas, and for three kinds of reflectors: metallic plane, 2D corner retro-reflector (2D-CR), and cubic corner retro-reflector (CCR). It is shown that an electromagnetic wave, reflected from a metallic plane and from a CCR, contains only “velocity-preserving” channels, whose phases are doubled in comparison with those of a single-passage propagation. At the same time, an electromagnetic wave reflected from a 2D-CR is shown to contain both “velocity-preserving” and “velocity-converting” channels, the latter converting the fast wave into the slow one and vice-versa. One characteristic feature of “velocity-converting” channels is that they reproduce the initial polarization state near the source, which might be of practical interest for plasma interferometry. In the case of circularly polarized modes, “velocity-preserving” channels completely disappear, and only “velocity-converting” channels are to be found.     

On the theory of electromagnetic surface waves in magnetized semiconductor plasma

The paper demonstrates existence of electromagnetic surface waves at the boundary separating a magnetized semiconductor plasma and a dielectric or metal. The external magnetic field is along the interface. As has been shown, slow surface waves of the helicon or Alfven type can exist only with their propagation vector directed obliquely with respect to the magnetic field. The ω-k relations have been found and ranges of existence established both in the frequency domain and that of angles between the propagation vector and the magnetic field.     

Stimulated Brillouin scattering of obliquely propagatingextraordinary electromagnetic waves off ion-Bernstein waves in plasmas

The parametric decay of an obliquely propagating extraordinary electromagnetic wave into another extraordinary electromagnetic wave and a low-frequency electrostatic ion-Berstein wave via the stimulated Brillouin scattering process is considered. Explicit expressions for the growth rate and threshold power for this instability are presented. Applications of the present investigation to fusion plasmas in the end cells of tandem mirrors and the magnetospheric and ionospheric plasmas to explain wave phenomena are pointed out. The dependence of threshold power on the pump wave angle is studied. The general expressions for the growth rate and threshold derived here can also be useful to explain future experimental data     

Filamentation instabilities associated with ordinary electromagnetic waves in collisional plasmas

It is shown that parametric coupling of an ordinary electromagnetic wave with purely damped convective cell modes as well as other collisional modes leads to purely growing perturbations in the direction perpendicular to the incoming radiation. The excitation of purely growing modes in a magnetized plasma is important because the resulting E × B drift can cause particle transport across the external magnetic field.