Anisotropic Magnetized Plasma Research Articles

Caustic region fields of an elliptical reflector covered by an anisotropic magnetized plasma layer

Theoretical formulations of the electromagnetic (EM) field distribution in the focal or caustic region of an elliptical reflector with its curved surface coated by collisional magnetized anisotropic plasma have been derived. Both parallel and perpendicular polarizations of the normal incident wave are considered. Expressions for the EM field intensity along the focal region have been obtained accurately using Maslov’s method. The effect of the plasma-layer thickness on the reflected and transmitted field intensity distributions was investigated. Other physical parameters such as the plasma electron density, the cyclotron frequencies, and the collisional frequency have been noticed to have an evident influence on the levels of the transmitted field-intensities along the focal region. The problem discussed in this paper has, also, been solved using Kirchhoff’s approximation and the results of the two methods are found to be in a good agreement.

Investigation on broadband propagation characteristic of terahertz electromagnetic wave in anisotropic magnetized plasma in frequency and time domain

In this paper, we investigate the propagation of terahertz (THz) electromagnetic wave in an anisotropic magnetized plasma by JE convolution-finite difference time domain method. The anisotropic characteristic of the plasma, which leads to right-hand circularly polarized (RCP) and right-hand circularly polarized (LCP) waves, has been taken into account. The interaction between electromagnetic waves and magnetized plasma is illustrated by reflection and transmission coefficients for both RCP and LCP THz waves. The effects of both the magnetized plasma thickness and the external magnetized field are analyzed and numerical results demonstrate that the two factors could influence the THz wave greatly. It is worthy to note that besides the reflection and transmission coefficients in the frequency domain, the waveform of the electric field in the time domain varying with thicknesses and external magnetic fields for different polarized direction has been studied.

Full-wave FEM simulations of electromagnetic waves in strongly magnetized non-homogeneous plasma

Electromagnetic wave propagation in anisotropic media has been widely studied over the last decades since there are several applications where anisotropy plays an important role. This paper presents a procedure to carry out three-dimensional (3D) finite element method (FEM) full-wave simulations of the electromagnetic field in inhomogeneous magnetized plasma of an electron cyclotron resonance ion source (ECRIS). We used COMSOL Multiphysics software and MATLAB to model a cold anisotropic magnetized plasma, described by full-3D non-uniform dielectric tensor, enclosed by the metallic cylindrical cavity where the plasma is formed. A proper mesh generation, exploiting FEM-based COMSOL versatility, allowed us to optimally model ECRIS cavity and microwave waveguide launching structure, with a good computational efficiency and high resolution of the solution especially around the resonance regions. Numerical simulations have been performed in the frequency domain: in the resonance regions especially, the material properties exhibit a spatial variation that leads to a large sparse ill-conditioned matrix which is solved by MUltifrontal Massively Parallel Solver (MUMPS) direct method. We implement a method to perform full-wave simulations considering a cold plasma model for the constitutive relations; the obtained results show that the presence of ECR layer, along with the cavity walls, strongly influences the shape and strength of the electromagnetic field distribution, featuring a strong non-uniformity of the main electromagnetic parameters.

Effect of Anisotropic Ion Pressure on Solitary Waves in Magnetized Dusty Plasmas

AbstractThe propagation of linear and nonlinear dust ion acoustic waves (DIAWs) are studied in a collisionless magnetized plasma which consists of warm ions having anisotropic thermal pressure, nonthermal (energetic) electrons and static dust particles of positive and negative charge polarity. The anisotropic ion pressure is defined using double adiabatic Chew‐Golberger‐Low (CGL) theory. In the linear regime, the propagation properties of the two possible modes are investigated via ion pressure anisotropy, dust particle polarity and nonthermality of electrons. Using reductive method Zakharov‐Kuznetsov (ZK) equation is derived for the propagation of two dimensional electrostatic dust ion acoustic solitary waves in dusty plasmas. It is found that both compressive and rarefactive solitons are formed in presence of nonthermal electrons using Cairn's distribution [R.A. Cairns, A.A. Mamun, R. Bingham, R.O. Dendy, R. Bostrom, C.M.C. Nairn and P.K. Shukla, Geophys.Res. Lett. 22, 2709 (1995)] in the system. The ion pressure anisotropy, nonthermality of electrons and charge polarity of the dust particles have significant effects on the amplitude and width of the dust ion acoustic solitary waves in such anisotropic nonthermal magnetized dusty plasmas. The numerical results are also presented for illustration. Our finding is applicable to space dusty plasma regimes having anisotropic ion pressure and nonthermal electrons. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

ANALYSIS OF PROPAGATION AND POLARIZATION CHARACTERISTICS OF ELECTROMAGNETIC WAVES THROUGH NONUNIFORM MAGNETIZED PLASMA SLAB USING PROPAGATOR MATRIX METHOD

An analytical technique referred to as the propagator ma- trix method (PMM) is presented to study the problem of electromag- netic (EM) waves interacting with the nonuniform magnetized plasma. In this method, the state vector is proposed to describe the characteris- tics of eigen waves in anisotropic medium, and state vectors at two dif- ferent locations are related with each other by the propagator matrix. This method can be used to deal with the phenomenon of the trans- formation of EM wave polarization induced by anisotropic magnetized plasma, besides the conventional propagation characteristics through plasma slab, which overcomes the drawback of other analytical meth- ods introduced in former studies. The EM problem model considered in this work is a steady-state, two-dimensional, nonuniform magne- tized plasma slab with arbitrary magnetic declination angle, which is composed of a number of subslabs. Each subslab has a flxed electron density, and the overall density proflle across the whole slab follows any practical distribution function. Based on PMM, a signiflcant feature of strong transformation of EM wave polarization is addressed when an incident wave normally projects on the slab, which leads to the re- ∞ected or transmitted waves containing two kinds of waves, i.e., the co-polarized wave and the cross-polarized wave. The efiects of vary- ing the plasma parameters on the re∞ected and transmitted powers of co-polarization and cross-polarization, as well as the absorptive power

Chorus wave-normal statistics in the Earth's radiation belts from ray tracing technique

Abstract. Discrete ELF/VLF (Extremely Low Frequency/Very Low Frequency) chorus emissions are one of the most intense electromagnetic plasma waves observed in radiation belts and in the outer terrestrial magnetosphere. These waves play a crucial role in the dynamics of radiation belts, and are responsible for the loss and the acceleration of energetic electrons. The objective of our study is to reconstruct the realistic distribution of chorus wave-normals in radiation belts for all magnetic latitudes. To achieve this aim, the data from the electric and magnetic field measurements onboard Cluster satellite are used to determine the wave-vector distribution of the chorus signal around the equator region. Then the propagation of such a wave packet is modeled using three-dimensional ray tracing technique, which employs K. Rönnmark's WHAMP to solve hot plasma dispersion relation along the wave packet trajectory. The observed chorus wave distributions close to waves source are first fitted to form the initial conditions which then propagate numerically through the inner magnetosphere in the frame of the WKB approximation. Ray tracing technique allows one to reconstruct wave packet properties (electric and magnetic fields, width of the wave packet in k-space, etc.) along the propagation path. The calculations show the spatial spreading of the signal energy due to propagation in the inhomogeneous and anisotropic magnetized plasma. Comparison of wave-normal distribution obtained from ray tracing technique with Cluster observations up to 40° latitude demonstrates the reliability of our approach and applied numerical schemes.

A 3-D Global Earth-Ionosphere FDTD Model Including an Anisotropic Magnetized Plasma Ionosphere

A 3-D global Earth-ionosphere finite-difference time-domain (FDTD) model is introduced that includes for the first time an anisotropic magnetized cold plasma ionosphere. All previous global FDTD Earth-ionosphere models to date have employed an isotropic conductivity profile. To generate the new model, a previously validated and published 3-D Cartesian magnetized cold plasma algorithm is adapted to the global latitude-longitude FDTD mesh that involves trapezoidal cells, merging of cells in the Polar regions, and triangular cells at the Poles. The global geomagnetic field, ionospheric particle densities and collision frequencies, as well as the Earth's topographic and bathymetric data are all mapped onto the global space grid. After a local high-resolution validation that demonstrates correct calculations of electromagnetic propagation in magnetized plasma, another numerical study is performed to validate the model on a global scale. This new model opens doors to a wide variety of advanced modeling for higher frequency and higher altitude electromagnetic phenomena and represents a paradigm shift from the commonly used ray-tracing codes. It also provides the opportunity to couple FDTD Earth-ionosphere models to other geophysical models, such as the Naval Research Lab's SAMI3, to yield a multiphysics simulator.

Exact nonlinear excitations in double-degenerate plasmas

In this work, we use the conventional hydrodynamics formalism and incorporate the Chew-Goldberger-Low double-adiabatic theory to evaluate the nonlinear electrostatic ion excitations in double-degenerate (electron spin-orbit degenerate) magnetized quantum plasmas. Based on the Sagdeev pseudopotential method, an exact general pseudopotential is calculated which leads to the allowed Mach-number range criteria for such localized density structures in an anisotropic magnetized plasma. We employ the criteria on the Mach-number range for diverse magnetized quantum plasma with different equations of state. It is remarked that various plasma fractional parameters such as the system dimensionality, ion-temperature, relativistic-degeneracy, Zeeman-energy, and plasma composition are involved in the stability of an obliquely propagating nonlinear ion-acoustic wave in a double-degenerate quantum plasma. Current study is most appropriate for nonlinear wave analysis in dense astrophysical magnetized plasma environments such as white-dwarfs and neutron-star crusts where the strong magnetic fields can be present.

Analysis on polarization characteristics of electromagnetic propagation in anisotropic magnetized plasma media

The electromagnetic (EM) wave propagation through an anisotropic magnetized plasma layer is studied using the finite-difference time-domain (FDTD) method based on the Runge–Kutta exponential time differencing (RKETD) technique. When the propagation direction of the EM wave is perpendicular to the external magnetic direction, Voigt effect should be considered. The RKETD–FDTD formulations are derived in detail and are confirmed by computing the reflection and transmission coefficients for the ordinary polarized wave and extraordinary polarized wave through a magnetized plasma slab. Excellent agreement between the numerical results and the exact analytical solutions is demonstrated. The EM wave become partly longitudinal and partly transverse in magnetized plasma medium due to the Voigt effect are also proved.

SPATIAL POWER SPECTRUM OF MULTIPLE SCATTERED ORDINARY AND EXTRAORDINARY WAVES IN MAGNETIZED PLASMA WITH ELECTRON DENSITY FLUCTUATIONS

Features of the spatial power spectrum (SPS) of multiple scattered ordinary and extraordinary waves in randomly inhomogeneous magnetized plasma are investigated using the smooth perturbation method taking into account difiraction efiects. Second order statistical moments are derived for arbitrary correlation function of electron density ∞uctuations at oblique illumination of magnetized plasma by mono-directed incident radiation. Numerical calculations have been carried out for anisotropic Gaussian correlation function taking into account anisotropy factor and angle of inclination of prolate irregularities with respect to the external magnetic fleld. It was shown that SPS has a double-peaked shape. External magnetic fleld narrows SPS for ordinary wave and the gap arises in the direction of prolate irregularities. For extraordinary wave the gap increases with a distance passing by the wave in anisotropic magnetized plasma, the width broadens and maximum slightly displaced.

IMPROVED SHIFT-OPERATOR FDTD METHOD FOR ANISOTROPIC MAGNETIZED COLD PLASMAS WITH ARBITRARY MAGNETIC FIELD DECLINATION

In this paper, a recently improved SO-FDTD (shift- operator flnite difierence time-domain) method is proposed and applied to the numerical analysis of the anisotropic magnetized plasma with arbitrary magnetic declination. By using the constitutive relation between polarized current density vector J and electric vector E and bringing the shift operators, the difierence iteration equations of fleld components for Maxwell equations are derived in detail. Furthermore, the memory requirement is decreased signiflcantly through incorporating a memory-minimized algorithm into the FDTD iterative cycles. The re∞ection and transmission coe-cients of electromagnetic wave through a magnetized plasma layer are calculated by using this method. It is shown that the new method not only improves accuracy but also produces speed and memory advantages over the SO-FDTD method in kDB coordinates system proposed in the recent reference. In addition, the recursion formulae of the improved SO-FDTD method are deduced and programmed easily and they involve no complex variables, so the computations for the magnetized plasma become very simple.

Spontaneously growing, weakly propagating, transverse fluctuations in anisotropic magnetized thermal plasmas

A new dispersion formalism describing the weakly propagating, transverse fluctuations with wave vectors (k⃗∥B⃗) parallel to the uniform background magnetic field B⃗ in an anisotropic bi-Maxwellian magnetized electron-proton plasma is presented. Different transverse right-handed or left-handed polarized modes can be excited, which are the whistler Weibel-like modes and the electron and proton firehose modes. Analytic instability threshold conditions are derived in terms of the combined temperature anisotropy A=T⊥/T∥, the parallel plasma beta β∥=8πnekBT∥/B2, and the electron plasma frequency phase speed w=ωp,e/(kc).

Effect of pressure anisotropy and flow velocity on Kelvin–Helmholtz instability of anisotropic magnetized plasma using generalized polytrope laws

The effect of pressure anisotropy and flow velocity on the Kelvin–Helmholtz (KH) instability of two magnetized anisotropic pressure plasmas flowing relative to each other is investigated using generalized polytrope laws. The anisotropic pressure with the generalized polytrope laws is considered with three-dimensional perturbations in the description of plasma using relevant magnetohydrodynamic (MHD) set of equations. The magnetic field is assumed in the x-direction and parallel to the direction of the flow of plasma streams. A complete polytrope model is given for the considered system in terms of pressure components, magnetic field, and density of the fluids to discuss the condition of KH instability, stability, and overstability. The problem is solved using the normal mode analysis and the general dispersion relation is obtained by applying the appropriate boundary conditions. The case of nonvanishing wavenumber transverse to the direction of the stream is obtained, which represents the stationery configuration without excitation of KH instability. The longitudinal mode of propagation is discussed with conditions of KH instability, stability, and overstability for collisionless (anisotropic) double-adiabatic Chew-Goldberger-Low (CGL) and collisional (isotropic) MHD media, depending on various values of polytrope indices. The effects of pressure anisotropy, different flow velocities, and magnetic field are also discussed on the growth rate of KH instability. We observe that the presence of flow velocity and pressure anisotropy of the plasmas has a destabilizing influence on the growth rate of the system. The growth rate is found larger for MHD set of equations in comparison to the CGL set of equations. The presence of magnetic field has a stabilizing role on the growth rate of the considered system.

LINEAR THEORY OF WEAKLY AMPLIFIED, PARALLEL PROPAGATING, TRANSVERSE TEMPERATURE-ANISOTROPY INSTABILITIES IN MAGNETIZED THERMAL PLASMAS

A rigorous analytical study of the dispersion relations of weakly amplified transverse fluctuations with wave vectors ($\vec{k}\parallel \vec{B}$) parallel to the uniform background magnetic field $\vec{B}$ in an anisotropic bi-Maxwellian magnetized electron-proton plasma is presented. We determine the conditions for which the weakly amplified LH-handed polarized Alfven-proton-cyclotron and RH-handed polarized Alfven-Whistler-electron-cyclotron branches can be excited. The results of our instability study are applied to the observed solar wind magnetic turbulence. The Alfvenic instability diagram explains well the main characteristic properties of the observed solar wind fluctuations. Especially, the observed confinement limits at small parallel plasma beta values are explained.

Analysis for scattering of conductive objects covered with anisotropic magnetized plasma by trapezoidal recursive convolution finite-difference time-domain method

The finite-difference time-domain method (FDTD) is extended to three-dimensional (3D) anisotropic magnetized plasma based on the trapezoidal recursive convolution (TRC) technology. The TRC technique requires single convolution integral in the formulation as in the recursive convolution (RC) method, while maintaining the accuracy comparable to the piecewise linear recursive convolution (PLRC) method with two convolution integrals. In this article, the numerical results indicate that the TRC-FDTD method not only improves accuracy over the RC-FDTD with the same computational efficiency but also spends less computational time than the PLRC-FDTD based on the same accuracy. The 3D TRC-FDTD formula is provided and the bistatic radar scattering sections of conductive targets covered with anisotropic magnetized plasma are calculated. The results show that magnetized plasma cover layer can greatly reduce echo energy of radar targets, and the anisotropic magnetized plasma cover has better absorption effect than nonmagnetized. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.

Linear Theory of Temperature Anisotropy Instabilities in Magnetized Thermal Pair Plasmas

A rigorous study of the dispersion relations of weakly amplified and weakly propagating transverse fluctuations with wave vectors ( � k � � B ) parallel to the uniform background magnetic field B in an anisotropic bi-Maxwellian magnetized pair plasma is presented. Earlier work, based on the weakly-amplified limit, is extended to the case of weakly propagating solutions, which includes in particular aperiodic fluctuations, by the appropriate Taylor expansion of the plasma dispersion function. It is shown that six different transverse right-handed (RH) and left-handed (LH) polarized modes can be excited whose dispersion relations and instability threshold conditions are derived. The existence and instability conditions are derived in terms of the combined temperature anisotropy A = T� / T� , the parallel plasma beta � =8 � nekBT� / B 2 and the electron plasma frequency phase speed w = p,e /( kc) . The pair Alfven and cyclotron instabilities are the only two weakly amplified solutions, whereas the four weakly propagating solutions are the mirror, firehose, cool magnetized Weibel and cyctronic fluctuations, respectively. The four weakly propagating solutions are aperiodic with vanishing real phase speeds R =0 if the plasma positrons and electrons have the same temperature anisotropy. The mirror and cool magnetized Weibel fluctuations reduce to the known hot and cool Weibel instabilities in the limit of an unmagnetized plasma.

An E-J Collocated 3-D FDTD Model of Electromagnetic Wave Propagation in Magnetized Cold Plasma

A new three-dimensional finite-difference time-domain (FDTD) numerical model is proposed herein to simulate electromagnetic wave propagation in an anisotropic magnetized cold plasma medium. Plasma effects contributed by electrons, positive, and negative ions are considered in this model. The current density vectors are collocated at the positions of the electric field vectors, and the complete FDTD algorithm consists of three regular updating equations for the magnetic field intensity components, as well as 12 tightly coupled differential equations for updating the electric field components and current densities. This model has the capability to simulate wave behavior in magnetized cold plasma for an applied magnetic field with arbitrary direction and magnitude. We validate the FDTD algorithm by calculating Faraday rotation of a linearly polarized plane wave. Additional numerical examples of electromagnetic wave propagation in plasma are also provided, all of which demonstrate very good agreement with plasma theory.

Wave instabilities in an anisotropic magnetized space plasma

We study wave instability in an collisionless, rarefied hot plasma (e.g. solar wind or corona). We consider the anisotropy produced by the magnetic field, when the thermal gas pressures across and along the field become unequal. We apply the 16-moment transport equations (obtained from the Boltzmann-Vlasov kinetic equation) including the anisotropic thermal fluxes. The general dispersion relation for the incompressible wave modes is derived. It is shown that a new, more complex wave spectrum with stable and unstable behavior is possible, in contrast to the classic fire-hose modes obtained in terms of the 13-moment integrated equations.

Runge-Kutta exponential time differencing FDTD method for anisotropic magnetized plasma

The electromagnetic propagation in anisotropic magnetized plasma slab is studied using the finite-difference time-domain method based on the Runge-Kutta exponential time differencing formulation (RKETD-FDTD). The high efficiency and accuracy of the method are confirmed by computing the reflection and transmission coefficients for the right-hand circularly polarized wave and left-hand circularly polarized wave through a magnetized plasma layer, with the direction of propagation parallel to the direction of the biasing field. The comparison of the numerical results of the RKETD, current density recursive convolution (CDRC), piecewise linear current density recursive convolution (PLCDRC), and exponential time differencing (ETD) with analytical values indicate that the RKETD method is the greatest accuracy and efficiency method among the above.

Wave Structure Functions of Multiply Scattered Electromagnetic Waves by Anisotropic Magnetized Turbulent Plasma Layer

Wave structure functions of both phase and logarithmic relative amplitude, their mutual wave structure functions for two plane electromagnetic waves with difierent frequencies are studied. Besides, features of intensity of frequency ∞uctuations of multiply scattered radiation by flnite thickness of anisotropic magnetized plasma layer are investigated in complex geometrical optics approximation. Source and receiver are assumed to be located on opposite sides with respect to turbulent plasma layer. Numerical calculations have been carried out for F-region of the ionosphere using satellite data of ionospheric plasma parameters. Wave structure functions for plane, spherical waves and Gaussian beams have been investigated in (1{4). Evolution of the angular power spectrum of scattered electromagnetic radiation and features of its statistical characteristics, broadening and displacements of its maximum has been studied in geometrical optics approximation (5{8). High-frequency monochromatic EM wave scat- tered on electron density ∞uctuations of ionospheric plasma lead to distortion of the observable angular power spectrum. Wave propagation in turbulent plasma with electron density ∞uctua- tions is usually accompanied by ∞uctuations of its parameters | amplitude, phase, intensity and so on. Investigation of peculiarities of frequency and frequency-spatial correlation functions are under the particular interest in satellite communications. It enables to deflne frequency band that could be transferred through statistically inhomogeneous medium without distortion of the form of signal spectrum. Determination of the frequency band demands the knowledge of frequencyspatial correlations of ∞uctuated fleld in the aperture plane of a highly directional antenna. In satel- lite communications, the ability to transmit a wideband data is closely related to the frequency correlation of the signal. Information about the frequency and spatial correlation of the signal is essential in designing and analyzing frequency and/or spatial diversity schemes. Therefore, in this paper, statistical characteristics: the log-amplitude and the phase wave structure functions, of frequency-spaced plane EM waves are computed. Complex geometrical optics approximation is applied taking into account multiple scattering efiects. Numerical calculations have been carried out utilizing satellite data of F-region ionospheric plasma parameters. 2. CORRELATION FUNCTION OF THE PHASE A point source, located in vacuum at a terminal distance l1 above from the plane boundary of random magnetized plasma, irradiate high-frequency electromagnetic waves. Thickness of the scat- tered layer is equal to l2, receiver is located in vacuum below the layer at a distant l3 in the XZ plane (principle plane) and the length of line-of-sight connecting the source and the receiver is L0 = l1 + l2 + l3. The imposed magnetic fleld makes an angle µ0 between Z axis and angle µ with the direction of a wavevector of the incident wave. The plasma concentration in the layer is: N(r) = N0 + N1(r); where N0-is the constant term, N1(r) is a random function of the spatial coordinates describing concentration ∞uctuations. We shall suppose that the inequalities are sat- isfled for magnetized plasma: !B ? !, !B ? eff, !B ? !p, where ! is the angular frequency, eff is the efiective collision frequency of electrons with other particles, !p = (4…e 2 N=m) 1=2 is the plasma frequency and !B = eB0=mc is the angular gyro-frequency for magnetic fleld; e and m are the charge and the mass of an electron, respectively, c is the speed of light in the vacuum. Plasma is considered as a uniaxial crystal having permittivity tensor components: ~