Showing papers on "Electromagnetic field published in 1986"

Electromagnetic wave theory

Abstract: A first year graduate text on electromagnetic field theory emphasizing mathematical approaches, problem solving and physical interpretation. Examples deal with guidance propagation, radiation, and scattering of electromagnetic waves; metallic and dielectric wave guides, resonators, antennas and radiating structures, Cerenkov radiation, moving media, plasmas, crystals, integrated optics, lasers and fibers, remote sensing, geophysical probing, dipole antennas and stratified media.

Tunnel ionization of complex atoms and of atomic ions in an altemating electromagnetic field

Abstract: An expression is derived for the probability of tunnel ionization, in an alternating field, of a complex atom and of an atomic ion that are in an arbitrary state. The expression for the tunnel-ionization probability is obtained in the quasiclassical approximation n* $1. Expressions are also obtained for states with arbitrary values of I at arbitrary ellipticity of the radiation. A quasiclassical approximation yields results up to values n * ~ 1, with accuracy up to several percent.

Tunnel Ionization Of Complex Atoms And Atomic Ions In Electromagnetic Field

Abstract: The expressions for tunnel ionization probability of the complex atoms and atomic ions from arbitrary states in electromagnetic field are obtained. These expressions correctly describe the experimental data on rare gases atoms ionization in an infrared electromagnetic field.

Electromagnetic scattering by arbitrary shaped three-dimensional homogeneous lossy dielectric objects

Abstract: The recent development and extension of the method of moments technique for analyzing electromagnetic scattering by arbitrary shaped three-dimensional homogeneous lossy dielectric objects is presented based on the combined field integral equations. The surfaces of the homogeneous three-dimensional arbitrary geometrical shapes are modeled using surface triangular patches, similar to the case of arbitrary shaped conducting objects. Further, the development and extensions required to treat efficiently three-dimensional lossy dielectric objects are reported. Numerical results and their comparisons are also presented for two canonical dielectric scatterers-a sphere and a finite circular cylinder.

Non-Classical States of the Electromagnetic Field

Abstract: A number of general features of non-classical states of light are reviewed. The phenomena of photon antibunching and sub-Poissonian photon statistics are then treated in more detail, including the experimental observations. Quantum effects in spontaneous parametric down-conversion are discussed, and recent experiments dealing with the time intervals between down-converted photons, with the intensity dependence of the cross-correlation function, and with the detection of a localized one-photon state are described. Finally, some quantum effects in the interference of light are discussed.

Nonlinear Optics and Quantum Electronics

Abstract: Partial table of contents: PART I: GENERAL CONCEPTS AND METHODS OF NONLINEAR OPTICS. Electromagnetic Fields. Classical Description. The Quantized Free Radiation Field. Interaction Between Radiation and Matter. Semiclassical Description of Nonlinear Optics. Statistical and Coherence Properties of the Radiation Field and Their Measurement. Nonstationary Processes. PART II: EFFECTS AND PROCESSES OF NONLINEAR OPTICS. Nonlinear One--photon Processes in Lasers. Nonlinearities in Transient One--photon Processes. Nonlinearities and Qunatum Phenomena in Transient One--photon Processes. Multiphoton Absorption and Emission. Generation of Harmonics and Sum and Difference Frequencies. Parametric Amplification and Oscillation. Stimulated Raman Scattering. Optical Bistability. APPENDIX A: Compilation of Quantum--Theoretical Definitions and Relations. General References. Index.

Different formulations for numerical solution of single or multibodies of revolution with mixed boundary conditions

Abstract: A numerical method for determining the electromagnetic field in the presence of one or several bodies of revolution is presented. The objects can be made of conductors, dielectrics or their combinations. The excitation is assumed to be due to a plane wave or infinitesimal electric dipoles located within or outside the dielectric. Several formulation types are considered and used to investigate the scattering by different objects. It is found that for moderate values of the dielectric constant, all formulation types give satisfactory results. However, for small or large relative permittivities the solution accuracies depend on the formulation type. As an application of the method to practical problems, two special cases of dielectric rod and microstrip antennas are considered. These antennas have widespread applications and the proposed method can be used to investigate their performance accurately.

Electromagnetic Fields Generated by Overhead and Buried Short Conductors Part 2 - Ground Networks

Abstract: The fundamental concepts and analytical development related to electromagnetic fields generated by a network consisting of cylindrical conductors arbitrarily located in a conducting homogeneous soil are described and discussed. This method is applicable to overhead conductor networks as well. A comprehensive sensitivity analysis based on the single and multiple point current injection techniques is conducted. In particular, the surface electric and magnetic fields caused by an impressed current between the center point and the four corner points of a grounding network is examined. The analysis is conducted for uniform and two-layer soils. The results show that the electric and magnetic fields can be used for detecting broken conductors. It is also shown that the longitudinal currents, leakage currents, earth potentials, and magnetic fields are influenced by frequency, points of current injection, and configuration of the network.

Electromagnetic instabilities driven by cool heavy ion beams

Abstract: The effects of the mass and density of cool, heavy ion beams on the linear and nonlinear characteristics of right-hand resonant and nonresonant electromagnetic ion beam instabilities are analyzed. The magnetic helicity and Alfven speed for a computer simulated complete linear dispersion equation for electromagnetic instabilities are examined. The data reveal that the maximum growth rate of the resonant mode and the threshold velocity of the nonresonant mode decrease with beam mass; however, the maximum growth rate of the nonresonant mode and the threshold velocity of the resonant mode are independent of the beam mass. The role reversal of the instabilities which occur when a heavy ion beam is the more dense component is studied. The nonlinear behavior of the instabilities is described; variations in the magnetic field fluctuation levels and the beam mass dependence are investigated. It is observed that at low beam density the magnetic field fluctuation level increases with beam mass and at higher beam density the fluctuation level correlates with the core mass. The instability data are applied to observations of Venus and the Comet Giacobini-Zinner.

Broad-Band Analysis of a Coaxial Discontinuity Used for Dielectric Measurements

Abstract: A coaxial line terminated by a gap is considered, the gap being filled with an unknown material. This cell enables measurements of complex permittivity of dielectric materials to be made. The relationship linking the measured admittance to the dielectric properties is obtained from a theoretical analysis of the electromagnetic field in the tine. The equivalent-circuit parameters of a coaxial line terminated by a gap are obtained all higher order waves excited at the discontinuity are taken into account. The measurements show good agreement between measured and calculated data from dc to 12.4 GHz.

Comparison of Quasi-Static and Exact Electromagnetic Fields from a Horizontal Electric Dipole Above a Lossy Dielectric Backed by an Imperfect Ground Plane

Abstract: In most microstrip transmission lines, analysis is made assuming that a quasi-TEM mode exists and propagates down the line. The primary objective of this paper is to obtain the region of validity of this assumption. The second objective of this paper is to derive the expressions for the fields for a horizontal electric dipole over a Iossy dielectric medium backed by an imperfect ground plane. It is shown that, to a first approximation, fields at the air-dielectric interface are independent of the ground plane conductivity. Since we are interested in coupfing between lines, our interest is in the computation of the fields primarily at the air-dielectric interface. Finally, numerical results are presented to show where the quasi-static approximations deviate from the exact solution for a given microstrip geometry as the frequency of operation or the observation point is changed.

Imaginary-time path integral for a relativistic spinless particle in an electromagnetic field

Abstract: A rigorous path integral representation of the solution of the Cauchy problem for the pure-imaginary-time Schrodinger equation ϖ t ψ(t, x)=−[H−mc 2]ψ(t,x) is established.H is the quantum Hamiltonian associated, via the Weyl correspondence, with the classical Hamiltonian [(cp−eA(x))2+m 2 c 4]1/2+eΦ(x) of a relativistic spinless particle in an electromagnetic field. The problem is connected with a time homogeneous Levy process.

Electromagnetic Fields Generated by Overhead and Buried Short Conductors Part 1 - Single Conductor

Abstract: The fundamental concepts and analytical development related to the low frequency electromagnetic fields generated by a single current-carrying conductor immersed in a medium of infinite extent and in a conducting half-space are described and discussed. It is shown that vertical conductors buried in earth are not detectable by above earth surface measurements of magnetic fields. Examples and numerical results involving energization of typical intact and broken single conductors are then described and commented on. It is shown that earth surface potentials and above earth magnetic fields are significantly distorted by a break in horizontal and oblique conductors. Finally, experimental measurements on a model with considerable heterogeneities confirm the significant influence of conductor discontinuities on the potential and magnetic field profiles.

Electromagnetic ion beam instabilities: Comparison of one- and two-dimensional simulations

Abstract: Numerical simulations of electromagnetic instabilities, driven by a cool tenuous ion beam propagating along an ambient magnetic field, have been conducted in one and two spatial dimensions. The calculations employ particle ions, fluid electrons, and a predictor corrector scheme for solving the electromagnetic field in two dimensions that is described in some detail. While the principal features of the one-dimensional calculations (which reproduce previous work) are retained, the two-dimensional simulations show some reduction of the overall level of the magnetic field fluctuations. Enhancement of the heating of the beam ions at the expense of the core ions also occurs in the case where the beam density is sufficiently large that the right-hand nonresonant instability dominates. Implications of the results for modeling of the ion foreshock and quasi-parallel shocks are discussed.

The Electromagnetic Field

Abstract: To describe how the capacitance and inductance per unit length of a transmission line determine the speed of an electrical pulse. To obtain an expression for pulse speed and characteristic impendance in a transmission line. To show that pulse speed is independent of geometry and with no dielectric or magnetic materials present is the same as the velocity of light. To suggest how electromagnetic waves can propagate. To mention special relativity as an alternative to magnetism.

Gaussian–Maxwell beams

Abstract: Gaussian-beam-type solutions to the Maxwell equations are constructed by using results from relativistic front analysis, and the propagation characteristics of these beams are analyzed. The rays of geometrical optics are shown to be the trajectories of energy flow, as given by the Poynting vector. The longitudinal components of the field vectors in the direction of the beam axis, though small, are shown to be essential for a consistent description.

The Near Field of an Insulated Dipole in a Dissipative Dielectric Medium (Short Paper)

Abstract: The near field of uninsulated dipole antenna in a dissipative dielectric medium is important in microwave hyperthermia and geophysical applications. In this paper, the electric field near an insulated dipole has been calculated by the direct numerical evaluation of a surface integral over the insulation. The computed results are compared with those previously obtained by an approximate numerical calculation.

Radiation and scattering from electrically small conducting bodies of arbitrary shape

Abstract: A simple moment solution is given for low frequency electromagnetic scattering and radiation problems. The problem is reduced to the corresponding electrostatic and magnetostatic problems. Each static problem is solved using the Method of Moments. The surface of the perfectly conducting scatterer is modeled by a set of planar triangular patches. Pulse expansion functions and point matching testing are used to compute the charge density in the electrostatic problem. For the magnetostatic current a set of charge-free vector expansion functions is used. The problem is formulated assuming the scatterer to be in an unbounded homogeneous region. Scatterers of various shapes, such as the circular disc, the sphere, and the cube are studied. Special attention is paid to a conducting box with a narrow slot. The computed results are the scattered fields, the induced charge and current distributions, and the induced electric and magnetic dipole moments. These are in close agreement with whatever published data are available.

Performance calculation for single-sided linear induction motors with a double-layer reaction rail under constant current excitation

Abstract: A method for computing the performance of a single-sided linear induction motor (SLIM) with a double-layer reaction rail, under constant current excitation, is presented. This method takes into account the reaction of secondary eddy currents on the airgap field, transverse edge and longitudinal end effects, together with skin effect, saturation, nonlinear magnetic permeability, and hysteresis in the solid steel core of a reaction rail. In an equivalent circuit of the machine, the mutual and secondary impedances are found from a solution of the two-dimensional electromagnetic field distribution. Modifying factors account for configurations in which the width of the secondary conductive layer is different from that of the steel core, and in which the thickness of the conductive overhand is different from that over the steel core. Good correlation is obtained between analysis and test results from a large-scale linear induction motor (LIM) at Queen's University. The developed expressions are appropriate for small and large LIM's and may also be used for constant voltage excitation conditions.

High Efficiency of the Penrose Process of Energy Extraction from Rotating Black Holes Immersed in Electromagnetic Fields

Abstract: The conditions are analyzed under which maximum efficiency is obtained for the Penrose process (PP) of energy extraction from rotating black holes immersed in electromagnetic fields. The components of the dipole magnetic field are displayed superposed on the background Kerr metric as a representative case. Mathematical methods for analyzing the disintegrational PP are developed, obtaining an equation to a mass-hyperbola defined by mass parameters of fragments resulting from the disintegration of a particle incident on the black hole. The efficiency of the PP is considered, analyzing all the factors contributing toward high efficiency along with the plausible astrophysical limits. In particular, it is shown that the incident particle splitting near the static limit of the Kerr geometry gives an efficiency from which 100 percent energy extraction efficiency can be assumed in constructing the PP-based model of the central engine in AGNs. Finally, the use of these techniques in modeling AGNs is discussed.

The Dirichlet-Neumann boundary control problem associated with Maxwell's equations in a cylindrical region

Abstract: In a cylindrical region we consider electromagnetic fields independent of the axial coordinate: controlling the time evolution of such fields by means of boundary currents, likewise independent of the axial direction, is equivalent to controlling, simultaneously, two wave equations; one with boundary control of Dirichlet type, the other of Neumann type. In this paper we provide a preliminary study of control problems of this type and indicate what is necessary for extensions of our work.

On the electromagnetic scattering from infinite rectangular grids with finite conductivity

Abstract: -The development of a new numerical technique for the analysis of electromagnetic scattering from a rectangular wire (or strip) mesh. According to this technique the conjugate gradient method (CGM) and the fast Fourier transform (FFT) are used to solved for the aperture fields and the induced current densities. The method is efficient because 1) it makes use of the fast Fourier transform, 2) it converts a set of integrodifferential equations into a set of algebraic equations, and 3) it does not require inversion of any matrices. Unlike the moment method, the spectral iteration approach (SIT), and the averaged boundary conditions method, this technique can be used for arbitrary size and spacing between adjacent strips. The equivalent radius principle is used to determine the reflection coefficient from a wire mesh. Results, examples, and comparisons of this method with other methods support the validity of the algorithm.

Electric and magnetic nuclear shielding tensors: A study of the water molecule.

Abstract: We introduce a series of new linear-response tensors which enable one to estimate the actual electric and magnetic fields at the nuclei of a molecule immersed in an external, spatially uniform, periodical electromagnetic field. The analysis is extended to the case of an electric field gradient. These tensors may be called electromagnetic nuclear shieldings. They possess interesting properties and fulfill a series of general sum rules and equations, showing the deep relations among the electromagnetic properties of molecules. An accurate numerical test has been performed on the water molecule, with use of the random-phase approximation to decouple the polarization propagator equations.

Oscillation center theory and ponderomotive stabilization of low-frequency plasma modes

Abstract: Nonlinear, nondissipative ponderomotive theory is developed in relation to recent experimental results showing that externally imposed rf fields can stabilize an axisymmetric mirror plasma. First, the ponderomotive force problem is reexamined, with emphasis on self‐consistency of the interaction between the plasma and high‐frequency field. The averaged action principle for the antenna–plasma system yields self‐consistent plasma and electromagnetic field dynamics on the oscillation‐center time scale. The plasma equilibrium condition is expressed as a balance among plasma and magnetic pressure forces, including interchange, ponderomotive, and magnetization forces. Next, the spectral stability of such static equilibria is studied in the low‐frequency magnetohydrodynamic (MHD) approximation, with a ΔW principle that incorporates the various ponderomotive contributions: particle effects, magnetization effects, and self‐consistent adjustment of the rf field resulting from displacements of the plasma away from equilibrium. The ponderomotive potential energy functional is related to the antenna inductance and antenna current amplitude. Finally, the noncanonical Hamiltonian formulation for the system’s dynamics is given, in terms of Eulerian fields. It allows the construction of nonlinearly conserved functionals, which yield criteria for linearized Lyapunov stability, for both multifluid and MHD models. The Lyapunov stability conditions are related to the modified ΔW variational principle.

Electromagnetic penetration into a conducting circular cylinder through a narrow slot, TM case

Abstract: A procedure is presented for calculating the electromagnetic field in the vicinity of an infinitesimally thin conducting circular cylindrical shell with an infinitely long slot illuminated by a TE plane wave. This field is the short-circuit field plus the field due to the slot. The short-circuit field is the field that would exist if there were no slot. The field due to the slot stems from the Φ -component of the electric field in the slot. Approximated by a linear combination of expansion functions that satisfy the edge conditions, this field component is determined by testing the equation of continuity of the axial magnetic field in the slot with non-negative powers of Φ where |Φ| is the angular distance from the center of the slot. Alternative expansion functions are introduced to preserve the accuracy of the solution in the vicinity of an internal resonance. Containing the resonant electric field, the first alternative expansion function is normalized so that its axial magnetic field remains finite as...