Showing papers on "Electromagnetic field published in 1984"
01 Jan 1984
TL;DR: The fundamental equations of the electrodynamics of continuous media are obtained by averaging the equations for the electromagnetic field in a vacuum as discussed by the authors, and the form of the equations and significance of the quantities appearing in them depend on the physical nature of the medium and on the way in which the field varies with time.
Abstract: Macroscopic electrodynamics is concerned with the study of electromagnetic fields in space that is occupied by matter. Electrodynamics deals with physical quantities averaged over elements of volume that are physically infinitesimal and ignore the microscopic variations of the quantities that result from the molecular structure of matter. The fundamental equations of the electrodynamics of continuous media are obtained by averaging the equations for the electromagnetic field in a vacuum. The form of the equations of macroscopic electrodynamics and the significance of the quantities appearing in them depend on the physical nature of the medium and on the way in which the field varies with time. Charges present in a conductor must be located on its surface. The presence of charges inside a conductor would cause an electric field in it. These charges can be distributed on its surface, however, in such a way that the fields that they produce in its interior are mutually balanced. The mean field in the vacuum is almost the same as the actual field. The two fields differ only in the immediate neighborhood of the body, where the effect of the irregular molecular fields is noticeable, and this difference does not affect the averaged field equations.
473 citations
TL;DR: In this paper, a vector H-field formulation is developed for electromagnetic wave propagation for a wide range of guided-wave problems, which is capable of solving microwave or optical waveguide problems with arbitrarily anisotropic materials.
Abstract: A vector H-field formulation is developed for electromagnetic wave propagation for a wide range of guided-wave problems. It is capable of solving microwave or optical waveguide problems with arbitrarily anisotropic materials. We have introduced infinite elements to extend the region of explicit field representation to infirdly, to consider open-type waveguides more accurately. Computed results are given for a variety of optical planar guides, image lines, and waveguides containing skew anisotropic dielectic.
293 citations
Book•
01 Jan 1984
TL;DR: The components of Theoretical Spectroscopy are discussed in this paper, where the effects of strong fields on matter are discussed as well as the effect of field fluctuation on Spectrograms.
Abstract: The Components of Theoretical Spectroscopy. Physical Effects of Strong Fields on Matter. Foundation of Laser Theory. Topics in Laser Spectroscopy. Effects of Field Fluctuations on Spectroscopy. Elements of Electromagnetic Field Quantization. References. Index.
234 citations
TL;DR: In this paper, the exact distributed image current function is obtained for the classical Sommerfeld half-space problem with vertical magnetic current source in complex space by applying the Laplace transform.
Abstract: Applying the Laplace transform, the exact distributed image current function is obtained for the classical Sommerfeld half-space problem with vertical magnetic current source. The resulting field integral is well behaved when the image current is situated in complex space. Unlike previous approximate images, the present theory is valid for any distance, height of the source, frequency, and half-space parameters. It is demonstrated that the present image theory reduces to the well-known dipole image at complex depth for large dielectric parameters of the half-space. Also, the reflection-coefficient method is obtained as a farfield approximation. Calculation of fields through exact image integration is seen to be simple and accurate and require modest computer capacity and time. In an appendix, some properties of the multivalued Green's function arising from a dipole source in complex space are also studied.
190 citations
TL;DR: In this paper, a vector transmission-line interpretation of the Fourier transformed problem with electric and magnetic fields instead of potential quantities is considered, where the image sources are seen to be located in complex space expressable in terms of a certain basic image current function, which was encountered in part II of this paper on the vertical electric dipole problem.
Abstract: The general Sommerfeld problem with both \epsilon and \mu discontinuous and a source consisting of arbitrarily oriented electric and/or magnetic dipoles at the same location is considered in terms of image theory. The problem is formulated with electric and magnetic fields instead of potential quantities resulting in a vector transmission-line interpretation of the Fourier transformed problem. The image sources are seen to be located in complex space expressable in terms of a certain basic image current function, which was encountered in part II of this paper on the vertical electric dipole problem. The horizontal electric/magnetic dipole image is solved and found to consist of both vertical and horizontal current components. The image concept is generalized to the most general three-dimensional sources. As a check, the well-known reflection coefficient method is obtained as the far-field approximation of the present theory.
181 citations
TL;DR: In this paper, basic considerations regarding the confinement of bound neutral systems of particles in limited regions of space by slowly varying electromagnetic fields are reviewed, and several specific cases are described briefly.
175 citations
TL;DR: In this paper, a numerical method for time-stepping Maxwell's equations in the two-dimensional (2-D) TE mode, which in a conductive earth reduces to the diffusion equation, is described.
Abstract: We describe a numerical method for time‐stepping Maxwell’s equations in the two‐dimensional (2-D) TE‐mode, which in a conductive earth reduces to the diffusion equation. The method is based on the classical DuFort‐Frankel finite‐difference scheme, which is both explicit and stable for any size of the time step. With this method, small time steps can be used at early times to track the rapid variations of the field, and large steps can be used at late times, when the field becomes smooth and its rates of diffusion and decay slow down. The boundary condition at the earth‐air interface is handled explicitly by calculating the field in the air from its values at the earth’s surface with an upward continuation based on Laplace’s equation. Boundary conditions in the earth are imposed by using a large, graded grid and setting the values at the sides and bottom to those for a haft‐space. We use the 2-D model to simulate transient electromagnetic (TE) surveys over a thin vertical conductor embedded in a half‐space...
169 citations
TL;DR: In this article, a moment solution to the electric field integral equation on the surface is presented for the electric current and electric charge induced on a perfectly conducting surface illuminated by an incident electromagnetic field.
Abstract: A new E -field solution is presented for the electric current and electric charge induced on a perfectly conducting surface illuminated by an incident electromagnetic field. This solution is a moment solution to the electric field integral equation on the surface. The expansion functions consist of a set of functions suitable for expanding the magnetostatic current and a set of functions whose surface divergences are suitable for expanding the electrostatic charge. The testing functions are similar to the expansion functions. With these expansion and testing functions, the new E -field solution works well with surfaces whose maximum dimension may be as small as 10^{-15} wavelengths or as large as a few wavelengths. Previous E -field solutions begin to deteriorate when the maximum dimension of the surface falls below a few hundredths of a wavelength. The new E -field solution is applied to a conducting circular disk and a conducting sphere.
155 citations
TL;DR: In this paper, an application of the boundary element method to two-dimensional electromagnetic field problems has been proposed, where calculations can be performed using far fewer nodes than by the finite element method, and unbounded field problems are easily treated without special additional consideration.
Abstract: This paper proposes an application of the boundary-element method to two-dimensional electromagnetic field problems. By this method, calculations can be performed using far fewer nodes than by the finite-element method, and unbounded field problems are easily treated without special additional consideration. In addition, the results obtained have fairly good accuracy. In this paper, analyzing procedures of electromagnetic field problems by the boundary-element method, under special conditions, are proposed and several examples are investigated.
143 citations
Patent•
27 Jun 1984TL;DR: In this article, an apparatus for treating a patient which induces an electric current in the body through external application of an electromagnetic field is described, which includes means for controlling the magnitude of the induced electric current by sensing the electromagnetic field and automatically controlling its strength.
Abstract: An apparatus for treating a patient which induces an electric current in the body through external application of an electromagnetic field. The apparatus includes means for controlling the magnitude of the induced electric current by sensing the electromagnetic field and automatically controlling its strength. The sensing may be accomplished through time multiplexed use of the field inducing coil or through the use of a separated, dedicated coil.
141 citations
TL;DR: In this article, an experimental system that consists of a metal-island film spaced a distance d from a continuous Ag film is described, and the dependence of the shift in the frequency of the island resonance on d shows good agreement with that predicted by a classical theory of the dipole-surface interaction.
Abstract: The resonance frequency of an electric dipole placed near a conducting surface is shifted by the dipole-surface interaction. The observation and measurement of these shifts at optical frequencies is reported for an experimental system that consists of a metal-island film spaced a distance d from a continuous Ag film. The dependence of the shift in the frequency of the island resonance on d shows good agreement with that predicted by a classical theory of the dipole-surface interaction.
TL;DR: In this paper, an analogous, one-dimensional system is considered consisting of a surface-state electron bound to the surface of liquid helium by its image charge, and a complete classical analysis of the behavior of this nonlinear oscillator in a microwave field is presented which shows that above a critical field strength the electron dynamics become chaotic and the electron diffuses in energy until it ionizes.
Abstract: In recent experimental investigations of the ionization of Rydberg atoms in low-frequency electromagnetic fields, ionization rates have been measured which depend strongly on the intensity of the oscillating fields but only weakly on the frequency. In an attempt to understand this ionization mechanism, an analogous, one-dimensional system is considered consisting of a surface-state electron bound to the surface of liquid helium by its image charge. A complete classical analysis of the behavior of this nonlinear oscillator in a microwave field is presented which shows that above a critical field strength the electron dynamics become chaotic and the electron diffuses in energy until it ionizes. Analytic estimates for the classical thresholds and rates for stochastic excitation and ionization are determined as functions of the microwave-field amplitude and frequency. Since the microwave frequencies and field strengths required for stochastic ionization of this one-dimensional "hydrogen" atom are readily available, this system provides an opportunity to thoroughly explore the manifestations of classical chaos in a quantum system.
TL;DR: In this paper, the authors describe the theory of a single sensor to perform simultaneous electric and magnetic near-field measurements using a loop antenna terminated with identical loads at two diametrically opposite points.
Abstract: This paper describes the theory of a single sensor to perform simultaneous electric and magnetic near-field measurements. The theory indicates that it is possible to measure the magnetic-loop and electricdipole currents using a loop antenna terminated with identical loads at two diametrically opposite points. The theory also indicates that it is possible to choose an ideal load impedance for achieving equal electric and magnetic-field responses of the loop. Preliminary experiments have been performed using a plane-wave field to verify these results.
TL;DR: In this paper, a finite-element analysis in which nonphysical spurious solutions do not appear has been established to solve the electromagnetic field problem of the closed waveguide filled with various anisotropic media.
Abstract: A finite-element analysis in which nonphysical spurious solutions do not appear has been established to solve the electromagnetic field problem of the closed waveguide filled with various anisotropic media. This method is based on the approximate extremization of a functional, whose Euler equation is the three-component curlcurl equation derived from the Maxwell equations, with a new conforming element. Specific examples are given and the results are compared with those obtained by exact solutions and longitudinal two-component finite-element solutions. Very close agreement was found and all nonzero eigenvalues have been proved to have one-to-one correspondence to the propagating modes of the waveguide.
TL;DR: In this article, a single surface integral equation for problems involving electromagnetic scattering from homogeneous dielectric bodies illuminated by time-harmonic sources is developed via the equivalence principle.
Abstract: A single surface integral equation for problems involving electromagnetic scattering from homogeneous dielectric bodies illuminated by time-harmonic sources is developed via the equivalence principle. The equation is formulated in terms of an equivalent electric current defined at the body surface. When allowed to radiate in a homogeneous medium having the material parameters of the exterior medium of the original problem, the electric current solution to the integral equation produces the correct scattered electric and magnetic fields external to the body.
TL;DR: In this paper, a singular integral equation of the first kind for one tangential vector field defined on the surface is proposed for the determination of the scattered and transmitted transient electromagnetic waves produced by a uniform dielectric body.
Abstract: The determination of the scattered and transmitted transient electromagnetic waves produced by a uniform dielectric body is reduced to the solution of a singular integral equation of the first kind for one tangential vector field defined on the surface. All derivations are carried out within the heuristic approach to Green functions and delta functions. The electric and magnetic fields are expressed in terms of the sources, initial values, and the boundary values by means of the Green function for the scalar wave equation. The appropriate integral equation is derived, and the integrals for the scattered and transmitted fields are given. The simpler problem of scattering of scalar waves is developed first. Formulas for the scattering of monochromatic fields are also given in the scalar and electromagnetic cases when transmitted fields do not vanish.
TL;DR: In this paper, the authors pointed out some problems with the usual quantum-mechanical theory of electrodynamics in nonlinear dielectric media which is used in non-linear optics.
Abstract: We point out some problems with the usual quantum-mechanical theory of electrodynamics in nonlinear dielectric media which is used in nonlinear optics. In order to understand these problems, the Hamiltonian formulation of the theory is examined. It is found that many of the difficulties in the usual theory are a result of the fact that the canonical momentum for the interacting theory is not the same as that for the free electromagnetic field theory.
TL;DR: In this paper, integro-differential equations are obtained for the electric and magnetic fields inside a linear, lossy, and anisotropic scatterer, in the frequency domain.
Abstract: Integro-differential equations are obtained for the electric and magnetic fields inside a linear, lossy, and anisotropic scatterer, in the frequency domain. The material of the scatterer is characterized by arbitrary values of the elements of the relative permittivity tensor \bar{\epsilon} , the relative permeability tensor \bar{\mu} , and the conductivity tensor \bar{\sigma} . The results are specialized to the case of oblique scattering in two dimensions, for which a numerically efficient computer code has been developed and tested, as described in a companion paper (Part II). The method developed herein is based on a comparison between macroscopic and microscopic descriptions of electromagnetic fields in material media, and is of general applicability.
TL;DR: In this article, an exhaustive integration of the type D vacuum and electrovac field equations with cosmological constant admitting a nonsingular aligned Maxwell field satisfying the generalized Goldberg-Sachs theorem is presented.
Abstract: We present an exhaustive integration of the type D vacuum and electrovac field equations with cosmological constant admitting a nonsingular aligned Maxwell field satisfying the generalized Goldberg–Sachs theorem. We derive a single expression for the general solution from which one may obtain all particular cases known until now in partial versions. We also investigate in detail the separability properties of the Hamilton–Jacobi equation for the charged particle orbits and of the Klein–Gordon equation for a massive charged spin‐zero test particle and their corresponding Killing tensors.
TL;DR: In this article, the time variation of the electric and magnetic field of the stripline having a comer is analyzed and the remarkable changing of distribution of the field is presented as a parameter of time and of conditions imposed by the corner stucture.
Abstract: The transient analysis of electromagnetic fields has shown its utility not only in clarifying the variation of the fields in time but also in gaining information on mechanisms by which the distributions of an electromagnetic field at the stationary state are bronght about. We have recently proposed a new numerical method for the transient analysis in three-dimensioual space by formulating the equivalent circuit based on Maxwell's equation by Bergeron's method. The resultant nodal equatiou is uniquely formulated in the equivalent circuit for both the electric field and the magnetic field. In this paper, we deal with the stripline which should be analyzed essentially in three-dimensionaf space because of its structure, The time variation of the electric and magnetic field of the stripline having a comer is analyzed and the remarkable changing of distribution of the field is presented as a parameter of time and of conditions imposed by the corner stucture.
TL;DR: In this paper, the position and intensity of a one-electron model atom in a circularly polarized field were derived for Coulomb-like and short-range potentials.
Abstract: The photoionization of atoms in a strong electromagnetic field leads to the effect of "above-threshold" ionization, displaying a number of peaks in the energy spectrum of the photoelectrons. In the case of a one-electron model atom in a circularly polarized field, we derive expressions that describe the position as well as the intensity of those peaks as a function of the field parameters by means of a nonperturbative method. It is immediately clear from our formulas that the lowest-energy peaks in general disappear with increasing field intensity, for Coulomb-like as well as shortrange potentials. For a zero-range potential, a numerical evaluation is easily performed, leading to results that are in every respect qualitatively similar to the experimental results obtained thus far on these kinds of processes.
01 Jan 1984
TL;DR: In this paper, the authors analyse some possible schemes to generate squeezed states of the electromagnetic field, i.e., states of non-nodes of the Glauber Sudarshan P representation of the radiation field.
Abstract: The coherent states of light have played a central role in quantum optics. They are minimum uncertainty states with their associated quantum noise randomly distributed in phase. That is, they have equal uncertainties in the two quadrature phase amplitudes of the electric field. Squeezed states on the other hand have phase sensitive quantum noise. The uncertainty in one quadrature phase is less than that in a coherent state. The possibility of achieving less quantum fluctuations in one quadrature phase than a coherent state, at the expense of course of increased fluctuations in the other quadrature phase has intriguing potential in low noise optical communication systems.1 Squeezed states of the electromagnetic field do not have a nonsingular representation in terms of the Glauber Sudarshan P representation. They may therefore be classified as non classical states of the radiation field. The present priority in this field is to generate and detect a light field which exhibits squeezing. In this paper we shall analyse some possible schemes to generate squeezed states.
TL;DR: In this paper, it was shown that the relativistic radiation reaction for an accelerating classical charge contains a term which exactly compensates the departure of the electromagnetic spectrum from Planckian form so as to bring the oscillator's behavior into precise agreement with the usual Planck's thermal form.
Abstract: In 1976 Unruh showed that a scalar quantum particle in a box accelerating through the vacuum of scalar quantum field theory responded as though it were in a thermal bath at temperature $T=\frac{\ensuremath{\hbar}a}{2\ensuremath{\pi}\mathrm{ck}}$. Here we show an analogous result within classical electromagnetic theory. A classical electric dipole oscillator accelerating through classical electromagnetic zero-point radiation responds just as would a dipole oscillator in an inertial frame in classical thermal radiation with Planck's spectrum at temperature $T=\frac{\ensuremath{\hbar}a}{2\ensuremath{\pi}\mathrm{ck}}$. In an earlier work it was shown that the electromagnetic field correlation functions for an observer accelerating through classical electromagnetic zero-point radiation correspond to a spectrum different from Planck's. The same spectrum is found in the quantum analysis of a vector field where the departure from Planckian form is assigned to the change in the number of normal modes associated with the event horizon of the accelerating observer. The present work shows that the relativistic radiation reaction for an accelerating classical charge contains a term which exactly compensates the departure of the electromagnetic spectrum from Planckian form so as to bring the oscillator's behavior into precise agreement with the usual Planckian thermal form.
TL;DR: In this article, an exact integral equation procedure for the interface problem and an asymptotic procedure for large conductivity are given. But these procedures are based on the perfect conductor problem.
01 May 1984
TL;DR: In this paper, the electromagnetic fields generated by vertical and horizontal electric dipoles near the boundary between air and the earth (salt or fresh water, soil, ice, etc.) are summarized in terms of a new unified theory of lateral-wave propagation.
Abstract: Lateral electromagnetic waves along a plane boundary between homogeneous half-spaces are reviewed. The electromagnetic fields generated by vertical and horizontal electric dipoles near the boundary between air and the earth (salt or fresh water, soil, ice, etc.) are summarized in terms of a new unified theory of lateral-wave propagation. Complete theoretically determined fields are displayed and compared with measured fields at f = 601 MHz relative to the boundary between air and salt water (σ = 3.5 S/m, e r = 80). Near, intermediate, and asymptotic fields are related graphically to the new general theory and to the approximate and restricted formulas of Norton and Banos as well as to the Zenneck wave. Application is made to the specific problem of communication with submerged submarines by means of transmitters consisting of electrically short monopoles in air and horizontal traveling-wave antennas and directional arrays in sea water. The properties of the antennas are evaluated in the frequency range 10 ≤ f ≤ 30 kHz which is optimum for receiver depths near 10 m, and at f = 1 kHz which is optimum for depths up to 50 m. The effects of reflections from the ionosphere and of the earth's curvature are not included.
TL;DR: In this paper, two stability criteria for discretization of the source type integrals are formulated to guarantee that the instability can be controlled by reducing the discretisation step, if they are met, and analyzed the solution of two two-dimensional electromagnetic scattering problems.
Abstract: The transient scattering of two-dimensional electromagnetic fields by an obstacle of finite extent is investigated with the aid of the time domain integral equation technique. In solving such equations with the marching-on-in-time method, numerical instabilities form a major problem. These instabilities can be attributed to errors in the discretization of the source type integrals that occur in the equations. In this paper, we formulate two so-called stability criteria for such a discretization that, if they are met, guarantee that the instability can be controlled by reducing the discretization step. With the aid of these criteria, we analyze the solution of two two-dimensional electromagnetic scattering problems, namely the scattering of a pulsed plane wave by a perfectly conducting and an inhomogeneous, lossy dielectric cylinder. Numerical results are presented and discussed.
TL;DR: In this paper, a nonlinear analysis of electromagnetic devices supplied by a sinusoidal alternating current or voltage source is presented, where the saturation effect is not taken into account for the design but does not affect widely the waveform of the current.
Abstract: A nonlinear analysis of electromagnetic devices supplied by a sinusoidal alternating current or voltage source is presented. In numerous apparatus like motors, generators, traveling field induction furnaces, etc., the saturation effect must be taken into account for the design but does not affect widely the waveform of the current which may be assumed sinusoidal. We shall present here a complex analysis based on the assumption of sinusoidal fields on two-dimensional geometries in Cartesian or axisymmetric coordinates.
25 Jun 1984
TL;DR: In this paper, simple and accurate formulas for the complete electromagnetic field generated by vertical and horizontal dipoles located on or near the boundary between two electrically different half-spaces such as air and water or rock and sea water are presented.
Abstract: Relatively simple and accurate formulas are now available for the complete electromagnetic field generated by vertical and horizontal dipoles located on or near the boundary between two electrically different half-spaces such as air and water or rock and sea water. The principal part of the field is an outward-traveling lateral wave with useful properties. The formulas are given and their application to a variety of problems reviewed briefly. These include: radio communication over the surface of the earth or sea, the wave antenna, communication with submarines using vertical dipoles in air and horizontal dipoles in the sea, the location of buried objects using horizontal dipoles on the surface of the earth, and the measurement of the conductivity of the sea floor.
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