Electromagnetic scattering by an inhomogeneous plasma anisotropic sphere of multilayers

Electromagnetic scattering by an inhomogeneous plasma anisotropic sphere is formulated and obtained, where the inhomogeneous plasma anisotropic sphere is divided into (s-1) homogeneous anisotropic spherical layers. The electromagnetic fields in the inner spherical multilayers and outer free space of the inhomogeneous plasma anisotropic spherical structure can be expanded in terms of the spherical vector wave functions in plasma anisotropic medium and in isotropic medium, respectively. By applying the continuous boundary conditions of electromagnetic fields on the spherical interfaces of the (s-1)-layered homogeneous anisotropic plasma medium, the unknown expansion coefficients of fields in the multilayered plasma spherical structure are obtained, and then the electromagnetic field distributions are calculated. Numerical results for the very general inhomogeneous plasma dielectric material sphere are given and the data in a special case are obtained using the present method and the method of moments accelerated with the conjugate-gradient fast-Fourier-transform approach and compared to each other to verify the correctness and applicability of the present analysis.     

Scattering by an infinite cylinder coated with an inhomogeneous and anisotropic plasma sheath

The problem of the interaction of an incidentHwave with an infinite conducting cylinder coated with an inhomogeneous and anisotropic plasma sheath is treated analytically. Numerical results for the farfield pattern of the scattered field as well as the backscattering cross sections are presented for various interesting ranges of the parameters involved. Detailed discussion of the effects of the impressed static magnetic field, the sheath thickness, and the density and profile of the plasma sheath on the scattered wave is also presented. A parabolic electron density profile is assumed.     

Diffraction by a perfectly conducting semi-infinite screen in an anisotropic plasma

The scattering of a plane electromagnetic wave by a perfectly conducting semi-infinite screen embedded in a homogeneous plasma is investigated. A uniform magnetic field is assumed to be impressed externally in a direction parallel to the edge of the half plane. The plasma is idealized to be a dielectric characterized by a tensor dielectric constant. The direction of the incident wave is assumed to be in a plane perpendicular to that of the screen. This vector problem is separable into two equivalent scalar problems for which either the electric or the magnetic vector is parallel to the edge of the half plane. It is found that for the case of theEmode, the magnetic vector parallel to the edge of the half plane satisfies a simple wave equation and a new type of impedance boundary condition on the screen. This problem is formulated in terms of an integral equation which specifies the current induced on the screen. The integral equation is of the Wiener-Hopf type and is solved by the usual function-theoretic methods. For a given orientation of the external magnetic field, a surface wave is found to exist along the screen but on one side only. The characteristics of this surface wave are determined.     

AGSM光束的聚焦

基于有扭曲的各向异性高斯-谢尔模型(AGSM)光束二阶矩矩阵的传输公式,研究了AGSM光束通过透镜的聚焦。作了详细的数值计算,说明聚焦AGSM光束的传输特性,包括光束参数和横向光强的变化,特别是扭曲项和空间相关长度对聚焦特性的影响。     

Measurement of antenna current distribution in an anisotropic plasma

The current distribution along a cylindrical antenna immersed in a magnetized plasma has been measured. It has been observed that the standing wavelength along the antenna wire is substantially shortened to a greater degree with increasing plasma frequency under the presence of the dc magnetic field. The gyroresonance has also been observed in the current distribution.     

Distortion of an electromagnetic pulse carrier propagating in an anisotropic homogeneous plasma

Transient signal propagation in anisotropic, homogeneous cold plasmas is considered. The anisotropy is caused by an external longitudinal magnetic field. Using the saddlepoint method of integration, an approximate expression for the electric field is obtained. The envelope of a distorted rectangular pulse carrier is plotted for various magnetic fields, including the isotropic case.     

Resonant scattering from a conducting cylinder clad with an anisotropic plasma

The scattering of an electromagnetic wave from a conducting cylinder clad with an anisotropic plasma of arbitrary electron density is considered, and the eigenfunction solution is obtained. The resonant behavior of the system is investigated. The resonant conditions are obtained, and damping of the resonant scattering by finite size effects and collisional dissipation is studied. The Rayleigh and geometrical optics limiting cases are derived, and the approach of the plasma scattering to that from a metallic body for increasing plasma frequency (electron density) is obtained. Comparisons with the scattering from an unclad cylinder and from a planar conductor sheathed with a plasma are made.     

On waves in an anisotropic plasma imbedded in a moving dielectric medium

The governing equations for electromagnetic fields in an anisotropic plasma imbedded in a moving dielectric medium are obtained. Examination of the wave and dispersion equations yields information on the elliptically or linearly polarized waves which may exist when the external magnetic field is parallel or perpendicular to the direction of motion, respectively.     

The field of a dipole enclosed in an elliptic anisotropic plasma cylinder

The boundary value problem for the field of an electric dipole enclosed in a thin elliptic anisotropic plasma cylinder with a vacuum cavity is considered. A solution to the problem is obtained and analyzed. The influence of a magnetic field and the cavity of variable size on the resonance electromagnetic field is studied in the case when the shape of the plasma cylinder’s cross section varies. The effect is compared to that observed in the case of a circular plasma cylinder.     

On the radiation field from an electric dipole in an anisotropic and compressible plasma medium

The radiation fields from an electric dipole in a homogeneous, anisotropic, and compressible plasma are considered. Using the Fourier transform method, the problem is formulated in terms of three scalar functions, each of which satisfies the two-dimensional inhomogeneous wave equation. Asymptotic expressions of the radiation fields are obtained for the integrals by the saddle point method of integration.     

Effects of electron-density distribution on the back scattering from an anisotropic plasma cylinder

The backscattering cross-section of a radially inhomogeneous plasma cylinder with an impressed axial static magnetic field is obtained for an incident H wave. The electron-density distribution is assumed to have a parabolic profile. Significant variation of the backscattering cross-section as a function of the density profile is found.     

Current distribution and input admittance of an infinite cylindrical antenna in anisotropic plasma

The current distribution and input admittance of an infinitely long cylindrical antenna driven by a slice generator and immersed in an anisotropic plasma are investigated. The applied dc magnetic field is along the axis of the antenna. By superimposing the characteristic waves guided along the antenna, the current solution is obtained in the form of a one-dimensional integral, which is examined both analytically and numerically. WhenK_{perp} > 0, the magnitude of the current decays slowly with the distance from the source, and its phase is nearly linear with a "propagation constant" equal tosqrt{K_{perp}}k_{0}for an antenna with very small radius. WhenK_{perp} < 0, the magnitude of the current decreases rapidly away from the source, and its phase is no longer linear. The input admittance decreases with the radius of the antenna.     

Waves along a cylindrical "Grid-like" antenna in an anisotropic compressible plasma

In an anisotropic compressible homogeneous plasma, the dispersion equation of waves along an infinitely long cylindrical "grid-like" antenna is obtained analytically. Numerical solutions of this equation show that an external static magnetic field has great influence upon the anomalously dispersive region of the dispersion relation around the plasma frequency.     

JEC-FDTD for 2-D conducting cylinder coated by anisotropic magnetized plasma

The JE convolution finite-difference-time-domain (JEC-FDTD) method is extended to the anisotropic magnetized plasma which incorporates both anisotropy and frequency dispersion at the same time, enabling the transient solution of the electromagnetic wave propagation in anisotropic magnetized plasmas. Two-dimensional JEC-FDTD formulations for magnetized plasma are derived. The back scattering radar cross section (RCS) of a perfectly conducting cylinder coated by a layer of magnetized plasmas is calculated.     

Scattering of plane waves by an anisotropic dielectric half-plane

Scattering of plane waves by a semi-infinite anisotropic thin dielectric layer is investigated, which can be considered as an example for electromagnetic energy absorbing materials. A pair of second-order boundary conditions is used to simulate an anisotropic thin dielectric layer as an infinitesimally thin sheet. Formulation is based on the Fourier integral transform technique, which reduces the scattering problem to two decoupled scalar Wiener-Hopf equations. Diffracted, reflected, and transmitted field terms are evaluated by using the Wiener-Hopf solutions that is obtained by the standard method. The uniqueness of the solution is satisfied by imposing an edge constraint in addition to the classical edge condition     

Scattering of electromagnetic pulse waves by conducting wedge in uniaxially anisotropic plasma

Asymptotic expansion for the transient response of radiation fields due to electric dipole located above the conducting wedge with an arbitrary angle embedded in a simple plasma is derived by using the saddle point method of integration. The transient time, which is defined as the time required to reach steady state, is discussed for various kinds of wedge angles and plasma frequencies.     

Impedance of a short horizontal dipole over a ground plane covered with an anisotropic plasma

Impedance of a short dipole antenna placed parallel over a ground plane covered with an anisotropic plasma has been studied by the quasistatic approximation with emphasis on the effects of image displacement for arbitrary inclinations of the static magnetic field. As the image location can move with the operating frequencies, the reflected characteristic conical surfaces can create oblique resonance anomalies, depending upon source dimensions and source location. While an oblique resonance occurs when the characteristic conical surface coincides with the dipole axis, another anomaly occurs when the reflected cone grazes the dipole ends.     

Radiation from a uniformly moving distribution of electric charge in an anisotropic, compressible plasma

The radiation characteristics of a linear distribution of electric charge moving with a uniform velocity in a homogeneous electron plasma of infinite extent are investigated for the case in which a uniform static magnetic field is impressed externally throughout the medium. The linear distribution of charge and its direction of motion are assumed to be parallel and perpendicular, respectively, to the direction of the external magnetic field. Of the two possible modes of waves of small amplitude, namely, the modified electromagnetic mode and the modified electron plasma mode, the uniformly moving charge distribution excites the modified electron plasma mode. The emitted radiation has no frequencies less than the plasma frequency. For a particular value of the ratio of the gyrotropic to the plasma frequency of the electrons, the frequency and the angular spectrum of the emitted radiation are determined for two values of the velocity of the charge.