Showing papers on "Electromagnetic field published in 1975"
TL;DR: In this paper, a numerical method for the solution of the electromagnetic fields within an arbitrary dielectric scatterer of the order of one wavelength in diameter is described, and an error of less than /spl plusmn/10 percent in locating and evaluating the standing wave peaks within the cylinder is achieved for a program execution time of 1 min.
Abstract: A numerical method is described for the solution of the electromagnetic fields within an arbitrary dielectric scatterer of the order of one wavelength in diameter. The method treats the irradiation of the scatterer as an initial value problem. At t = 0, a plane-wave source of frequency f is assumed to be turned on. The diffraction of waves from this source is modeled by repeatedly solving a finite-difference analog of the time-dependent Maxwell's equations. Time stepping is continued until sinusoidual steady-state field values are observed at all points within the scatterer. The envelope of the standing wave is taken as the steady-state scattered field. As an example of this method, the computed results for a dielectric cylinder scatterer are presented. An error of less than /spl plusmn/10 percent in locating and evaluating the standing-wave peaks within the cylinder is achieved for a program execution time of 1 min. The extension of this method to the solution of the fields within three-dimensional dielectric scatterers is outlined.
1,300 citations
TL;DR: The theory of random electrodynamics as mentioned in this paper is a classical electron theory involving Newton's equations for particle motion due to the Lorentz force, and the equations for the electromagnetic fields with point particles as sources.
Abstract: The theory of classical electrodynamics with classical electromagnetic zero-point radiation is outlined here under the title random electrodynamics. The work represents a reanalysis of the bounds of validity of classical electron theory which should sharpen the understanding of the connections and dinstinctions between classical and quantum theories. The new theory of random electrodynamics is a classical electron theory involving Newton's equations for particle motion due to the Lorentz force, and Maxwell's equations for the electromagnetic fields with point particles as sources. However, the theory departs from the classical electron theory of Lorentz in that it adopts a new boundary condition on Maxwell's equations. It is assumed that the homogeneous boundary condition involves random classical electromagnetic radiation with a Lorentz-invariant spectrum, classical electromagnetic zero-point radiation. The scale of the spectrum of random radiation is set by Planck's constant $\ensuremath{\hbar}$. In the limit $\ensuremath{\hbar}\ensuremath{\rightarrow}0$, the theory of random electrodynamics becomes Lorentz's theory of electrons. Thus, random electrodynamics stands between two well-known theories\char22{}traditional classical electron theory with $\ensuremath{\hbar}=0$ on the one hand and quantum electrodynamics with its noncommuting operators on the other. The paper discusses the role of boundary conditions in classical electrodynamics, the motivation for choosing a new boundary condition involving classical zero-point radiation, and the assumed random character of the radiation. Also, the implications of the theory of random electrodynamics are summarized, including the detection of zero-point radiation, the calculation of van der Waals forces, and the change of ideas in statistical thermodynamics. In these cases the summary accounts refer to published calculations which yield results in agreement with experiment. The implications of random electrodynamics for atomic structure, atomic spectra, and particle-interference effects are discussed on an order-of-magnitude or heuristic level. Some detailed mathematical connections and some merely heuristic connections are noted between random electrodynamics and quantum theory.
272 citations
Book•
01 Jan 1975
TL;DR: The Poynting Theorem and Electromagnetic Power Mode Theory of Waveguides TEM Waves on Two-Conductor Transmision Lines Phasor Analysis of Reflective Transmison Lines Radiation from Antennas in Free Space Appendixes as mentioned in this paper.
Abstract: Vector Analysis and Electromagnetic Fields in Free Space Vector Differential Relations and Maxwell's Differential Relations in Free Space Maxwell's Equations and Boundary Conditions for Material Regions at Rest Static and Quasi-Static Electric Fields Static and Quasi-Static Magnetic Fields Wave Reflection and Transmission at Plane Boundaries The Poynting Theorem and Electromagnetic Power Mode Theory of Waveguides TEM Waves on Two-Conductor Transmision Lines Phasor Analysis of Reflective Transmision Lines Radiation from Antennas in Free Space Appendixes Index.
243 citations
01 Jan 1975
TL;DR: In this article, the electromagnetic fields within a detailed model of the human eye and its surrounding bony orbit are calculated for two different frequencies of plane-wave irradiation: 750 MHz and 1.5 GHz.
Abstract: The electromagnetic fields within a detailed model of the human eye and its surrounding bony orbit are calculated for two different frequencies of plane-wave irradiation: 750 MHz and 1.5 GHz. The computation is performed with a finite-difference algorithm for the time-dependent Maxwell's equations, carried out to the sinusoidal steady state. The heating potential, derived from the square of the electric field, is used to calculate the temperatures induced within the eyeball of the model. This computation is performed with the implicit alternating-direction (IAD) algorithm for the heat conduction equation. Using an order-of-magnitude estimate of the heat-sinking capacity of the retinal blood supply, it is determined that a hot spot exceeding 40.4/spl deg/C occurs at the center of the model eyeball at an incident power level of 100 mW/cm/sup 2/ at 1.5 GHz.
238 citations
TL;DR: In this paper, a form of quantum electrodynamics is developed which allows us to treat a number of problems involving dielectric and conducting surfaces, the presence of which leads to new observable effects.
Abstract: A form of quantum electrodynamics is developed which allows us to treat a number of problems involving dielectric and conducting surfaces, the presence of which leads to a number of new observable effects. A number of suitably defined response functions play a basic role in the present approach, as these in conjunction with the fluctuation-dissipation theorem lead to electromagnetic field correlation functions, which describe physical effects such as lifetimes, frequency shifts of the excited states, dispersion forces, etc. The quantization of the electromagnetic field is only implicitly used. A large part of the present paper is devoted to the calculation of the response functions involving different geometries and various types of dielectrics. Both spatially dispersive and spatially nondispersive dielectrics are considered. The response functions are calculated using Maxwell's equations and the usual boundary conditions at the interface adjoining the two mediums. As a first application of the present approach, the black-body fluctuations in finite geometries and the influence of surfaces on its temporal and spatial coherence are studied. An interesting theorem is also proved which enables us to calculate the normally ordered (antinormally ordered) correlation functions from the symmetrized correlation functions.
237 citations
TL;DR: In this article, the electromagnetic fields within a detailed model of the human eye and its surrounding bony orbit are calculated for two different frequencies of plane-wave irradiation: 750 MHz and 1.5 GHz.
Abstract: The electromagnetic fields within a detailed model of the human eye and its surrounding bony orbit are calculated for two different frequencies of plane-wave irradiation: 750 MHz and 1.5 GHz. The computation is performed with a finite-difference algorithm for the time-dependent Maxwell's equations, carried out to the sinusoidal steady state. The heating potential, derived from the square of the electric field, is used to calculate the temperatures induced within the eyeball of the model. This computation is performed with the implicit alternating-direction (IAD) algorithm for the heat conduction equation. Using an order-of-magnitude estimate of the heat-sinking capacity of the retinal blood supply, it is determined that a hot spot exceeding 40.4/spl deg/C occurs at the center of the model eyeball at an incident power level of 100 mW/cm/sup 2/ at 1.5 GHz.
225 citations
01 Nov 1975
Abstract: A recently developed formulation of the inverse source problem as a Fredholm integral equation of the first kind provides motivation for the development of analytical characterizations of the nonuniqueness in the inverse source problem. Nonradiating sources, i. e., sources for which the field is identically zero outside a finite region, are introduced. It is then shown that the null space of the Fredholm integral equation is exactly the class of nonradiating sources.
219 citations
194 citations
Patent•
24 Feb 1975
TL;DR: In this article, the maximum intensity vector of a magnetic field produced by the currents in the coils nutates about a mean axis called the pointing vector direction of the field, which is used to both track or locate an object in addition to determining the relative orientation of this object.
Abstract: A field (e.g., a magnetic field) which nutates about a pointing vector is used to both track or locate an object in addition to determining the relative orientation of this object. Apparatus for generating such a field includes mutually orthogonal coils and circuitry for supplying an unmodulated carrier, hereafter called DC signal, to one coil and an AC modulated carrier signal, hereafter called AC signal, to at least one (usually two) other coil, such that the maximum intensity vector of a magnetic field produced by the currents in the coils nutates about a mean axis called the pointing vector direction of the field.
184 citations
TL;DR: In this paper, the process of vacuum polarization in the field of a "bare" Kerr-Newman geometry is studied and the value of the critical strength of the electromagnetic fields is given together with an analysis of the feedback of the discharge on the geometry.
Abstract: Following the classical approach of Sauter, of Heisenberg and Euler and of Schwinger the process of vacuum polarization in the field of a "bare" Kerr-Newman geometry is studied. The value of the critical strength of the electromagnetic fields is given together with an analysis of the feedback of the discharge on the geometry. The relevance of this analysis for current astrophysical observations is mentioned.
TL;DR: In this article, the Lagrangian equations of motion for a spinning particle having arbitrary multipole structure in arbitrary external fields are derived and the complete system of field equations can be recovered from a fourdimensional action integral representing a polarized dust-like medium interacting with an arbitrary set of fields.
Abstract: The general form of the Lagrangian equations of motion is derived for a spinning particle having arbitrary multipole structure in arbitrary external fields. It is then shown how these equations, together with the complete system of field equations can be recovered from a fourdimensional action integral representing a polarized dustlike medium interacting with an arbitrary set of fields. These general results are then specialized to the case of Einstein-Maxwell fields in order to obtain the general-relativistic extension of Lorentz's dielectric theory.
TL;DR: In this article, one-loop effective potentials for elementary systems placed in a strong magnetic or a laser-produced electromagnetic environment are computed for the case where the system can make transitions from a spontaneously broken asymmetric phase to restored symmetry.
01 Jan 1975
TL;DR: In this article, the Coulomb law states that the field produced by a point charge is inversely proportional to the square of the distance from the charge to the point of interest.
Abstract: Publisher Summary
This chapter discusses constant electromagnetic fields. For a constant electric field, the Coulomb law states that field produced by a point charge is inversely proportional to the square of the distance from the charge. If there is a system of charges, then the held produced by this system is equal, according to the principle of superposition, to the sum of the fields produced by each of the particles individually. In determining the energy of a system of charges, it is started from the energy of the field, that is, from the expression for the energy density. From the Larmor's theorem, the derivative of average angular momentum (M) of the system is equal to the moment (K) of the forces acting on the system. If the e/m ratio is the same for all particles of the system, the angular momentum and magnetic moment are proportional to one another. The vector M¯ (and with it the magnetic moment m¯) rotates with angular velocity –Ω around the direction of the field, while its absolute magnitude and the angle that it makes with this direction remain fixed.
01 Dec 1975
TL;DR: In this article, a general 3-dimensional medium may be represented by a simple model made up of generalised 2-dimensional nodes, which is then used for the numerical solution of electric and magnetic vector fields within the medium, without any mathematical formulation of the problem.
Abstract: The paper shows how a general 3-dimensional medium may be represented by a simple model made up of generalised 2-dimensional nodes. It is then shown how this model may be used for the numerical solution of electric and magnetic vector fields within the medium, without any mathematical formulation of the problem. Results for the resonant frequencies and power decay times of some cavities partially filled with dielectric are given using this method. There has been an excellent agreement in all cases where comparisons could be made.
TL;DR: In this article, a detailed experimental and theoretical study into the response of a 2-layer, plane-stratified, low-loss dielectric earth is presented, and the experimental results are useful in turn in demonstrating the reliability of approximate theoretical solutions for the electromagnetic fields about the dipole obtained by normal mode and geometrical optics methods.
Abstract: The use of the radio interferometry method requires a detailed understanding of the nature of electromagnetic wave propagation in structures composed of materials with low electrical loss. This paper contains the results of a detailed experimental and theoretical study into the response of a 2-layer, plane-stratified, low-loss dielectric earth. The technique used to construct a scale model with microwave equipment to experimentally simulate the 2-layer structure response is discussed. The wave nature of the response derived from the theoretical investigations is used to interpret the features of the experimental results. The experimental results are useful in turn in demonstrating the reliability of approximate theoretical solutions for the electromagnetic fields about the dipole obtained by normal mode and geometrical optics methods. Such features as (1) the modification of the dipole radiation pattern seen when the antenna is placed at the interface between media of differing electrical properties, and (2) the development of guided and leaky modes in the layered structure are examined in detail.
TL;DR: In this paper, the linear theory of a cold relativistic electron beam propagating parallel to an external magnetic field and through a cold, homogeneous plasma is investigated, and the electromagnetic dispersion relation is solved numerically and compared with analytical predictions based on the electrostatic approximation.
Abstract: The linear theory of a cold relativistic electron beam propagating parallel to an external magnetic field and through a cold, homogeneous plasma is investigated. The electromagnetic dispersion relation is solved numerically and compared with analytical predictions based on the electrostatic approximation. It is found that electromagnetic effects are important for determining the entire unstable spectrum. However, except for the strong magnetic field regime, the maximum growth rates and corresponding frequencies are in agreement with those predicted by the electrostatic approximation. In the strong magnetic field regime the two−stream spectrum is found to be much narrower in angle than predicted by the electrostatic approximation. In the moderate and strong magnetic field regime the growth rate of waves propagating at large angles with respect to the beam are independent of beam energy.
TL;DR: In this article, a theory is presented that describes the time evolution of the diffraction properties of holographically formed thick phase gratings in ferroelectrics, particularly in iron-doped lithium niobate, based upon a model that relates the instantaneous electromagnetic fields in a grating to the refractive index in a manner consistent with the work of Young et al.
Abstract: A theory is presented that describes the time evolution of the diffraction properties of holographically formed thick phase gratings in ferroelectrics, particularly in iron‐doped lithium niobate. The theory is based upon a model that relates the instantaneous electromagnetic fields in a grating to the refractive index in a manner consistent with the work of Young et al.; that is, the index modulation amplitude is proportional to the product of the amplitudes of the writing fields, while index maxima and intensity maxima are spatially shifted by some fraction of a fringe. The model leads to coupled nonlinear equations for the writing fields that are analogous to the linear equations of Kogelnik, and in certain limits, yield identical results. Closed‐form solutions of the coupled nonlinear equations are found to describe the interaction between writing beams observed by Staebler and Amodei, as well as the time evolution of diffraction efficiency observed by Amodei et al. In conjunction with the latter exper...
TL;DR: In this paper, a tensor tensor formalism and associated exterior calculus are developed for the electromagnetic case, on which a discussion of the treacherous character of the continuum limit is based.
Abstract: The ’’Regge calculus’’ approach is extended to the electromagnetic case. To this end an ’’affine’’ tensor formalism and associated exterior calculus are developed. The simplicial approach to linear field equations is illustrated by the two‐dimensional scalar wave equation, on which also a discussion of the treacherous character of the continuum limit is based.
TL;DR: In this article, the propagation and radiation of electromagnetic waves from oscillating sources in a suddenly created plasma are studied in detail and field expressions are derived through the use of Laplace transformations.
Abstract: Propagation and radiation of electromagnetic waves from oscillating sources in a suddenly created plasma are studied in this investigation. Field expressions are derived through the use of Laplace transformations. The spatial distribution of sources is taken to be arbitrary but confined. Two cases are considered in detail: 1) plane wave propagation in a source-free region and 2) electric point dipole radiation. In the case of plane wave propagation, various aspects such as wave split, frequency shift, phase and group velocities, amplitude changes, power flows, and energy relations are discussed. In the case of electric dipole radiation, the electromagnetic fields and instantaneous radiated power are calculated and expressed in terms of Lommel functions of two variables. Asymptotic expressions and graphical results of numerical calculations of these quantities are presented. Many interesting properties of the spherical waves and power radiation are discussed.
TL;DR: The sensitivity of the electrooptic and magnetooptic methods is analyzed and new figures of merit for materials used as sensors in these applications are derived.
Abstract: Vector components of alternating electric and magnetic fields can be measured with excellent sensitivity and time resolution using a laser system employing Pockels effect or Faraday effect materials as field sensors. This technique offers the advantages of being passive and remote; the sensor material requires no power source and can be interrogated by a remotely located laser transmitter and receiver with no connecting wires or electrodes. This paper analyzes the sensitivity of the electrooptic and magnetooptic methods and derives new figures of merit for materials used as sensors in these applications. Experiments evaluating the temperature coefficients of sensitivity and demonstrating that sensitivities of 0.06 V/cm and 0.5 G can be achieved easily are described.
TL;DR: In this paper, the surface-dependent correction terms for the case of a small blackbody bounded by two plane conducting surfaces are derived and a straightforward perturbation theory is used to obtain one-photon transition probabilities in terms of the surfacedependent response functions.
Abstract: In this paper the physical entities such as transition probabilities and the density of states are related to appropriate electromagnetic-field correlation functions and to appropriate response functions. Such response functions have already been computed in a previous paper and therefore these can be used to obtain surface-dependent corrections. It is shown how the density of states and hence Planck's law depends on the presence of surfaces. I explicitly calculate the correction terms for the case of a small blackbody bounded by two plane conducting surfaces. An appreciable correction occurs if the linear dimensions of the blackbody are of the order of a wavelength. Next electric-dipole-type transitions in atomic systems are considered and a straightforward perturbation theory is used to obtain one-photon transition probabilities in terms of the surface-dependent response functions. As an illustration of the surface-dependent terms, the transitions in presence of a conducting surface are considered. The transition probabilities show a marked increase or decrease depending on whether the dipole transition is parallel or perpendicular to the surface. Both stationary and nonstationary fields are considered. As a special case of nonstationary fields, the transitions in a coherent field are considered in detail. It is also shown how the coherent radiation field in presence of dielectrics can be realized. It is found that if the radiation field, in arbitrary geometries, is initially in vacuum state then at later times it would be found in a coherent state if perturbed by an external ($c$-number) electromagnetic field.
TL;DR: In this paper, a previously developed electromagnetic field perturbation analysis is used to calculate the electric fields in tissue prolate spheroids irradiated by plane waves with long wavelength compared to the spheroid dimensions.
Abstract: A previously developed electromagnetic (EM) field perturbation analysis is used to calculate the electric fields in tissue prolate spheroids irradiated by plane waves with long wavelength compared to the spheroid dimensions. This theory is applied to prolate spheroid models of man and animals to obtain internal electric field strength, absorbed power distribution, and total absorbed power. These data are of value in estimating tissue EM power absorption in experimental animals and man. The theory may be used to help extrapolate animal biological effects data to man, and as a guide to establishing an EM radiation safety standard.
TL;DR: In this article, the concept of minimal coupling, which leads to the Schrodinger equation of a particle in an external electromagnetic field, is reformulated within the theory of complex line bundles.
Abstract: The concept of minimal coupling, which leads to the Schrodinger equation of a particle in an external electromagnetic field, is reformulated within the theory of complex line bundles. The possible generalizations are discussed, and the case of the magnetic monopole is investigated with the help of the new formalism.
TL;DR: In this paper, an exact solvable model describing the interaction between a two-level system and the electromagnetic field is presented, and the model is shown to be exactly solvable for long interaction times.
Abstract: We present an exactly solvable model describing the interaction between a two-level system and the electromagnetic field. For long interaction times we evidence some purely quantum-mechanical effects, such as the destruction of coherence of radiation and the Gaussian envelope of the transition probability.
TL;DR: In this paper, the authors proposed a method to measure the magnetic field strength above an ocean surface by measuring the wave spectra of a progressive ocean wave in a horizontally stratified ocean, which is a summation of a transverse electric type field, transverse magnetic type field and an electrostatic type field.
Abstract: The electromagnetic field generated by a progressive ocean wave in a horizontally stratified ocean is a sum of a transverse electric type field, a transverse magnetic type field, and an electrostatic type field. Seawater velocity components in a vertical plane containing the direction of wave propagation generate the transverse electric part of the field, and the velocity component normal to the plane generates the transverse magnetic part of the field, which vanishes above an ocean surface. The electrostatic part of the field results from surface charges that halt vertical electric currents at an ocean surface. Gradients of magnetic fields generated at the surface by both surface and internal waves provide sensible signals for recently developed magnetic gradiometers based on the Josephson effect, provided surface speeds exceed 1 cm/s or so. Vertically spaced measurements of noise spectra of magnetic field gradients above an ocean surface offer a unique and promising means of obtaining a measure of surface and internal wave spectra for three reasons: (1) magnetic field strengths above the surface are proportional to a weighted average of seawater speed over an ocean depth, which provides a response depending on the mode structure of internal waves; (2) field strengths decrease exponentially with height above the surface as e−kh, where k denotes wave number, which provides means of wave number discrimination and, together with frequency discrimination, offers means of resolving internal wave spectra mode by mode; and (3) noise spectra of magnetic field gradients are effectively cross spectra and so provide directional information on wave spectra from an effective point measurement.
01 Oct 1975
TL;DR: In this paper, a simple matrix equation for the currents induced in arbitrary termination networks is obtained for a two-wire transmission line illuminated by a non-uniform electromagnetic field, which is extended to multiconductor lines.
Abstract: A well-known result [1], [2] for the response of a two-wire transmission line illuminated by a nonuniform electromagnetic field is extended to multiconductor lines. A simple matrix equation for the currents induced in arbitrary termination networks is obtained. Air Development Center.
TL;DR: In this article, the elastic scattering amplitude, taking into account the mass correction to the propagation function, is found for electrons interacting with an intense electromagnetic field characteristic of nonlinear quantum electrodynamics.