Electromagnetic Field Components Research Articles

Proposal for the generation of an ion vortex beam and study of its electromagnetic fields

We propose a scheme for the generation of an ion vortex beam and we study the properties of its electromagnetic field on a plane transverse to its propagation direction. The ion vortex is created by the diffraction of an ionic beam by a light mask with a spiral-like transverse intensity pattern. The diffraction is a result of a short time optical dipole interaction between the light mask and the ion which results to a phase imprint on the ionic wave function. It is shown that as the order of the vortex states that are generated by the various diffraction gets higher the electromagnetic field components have reduced magnitudes. The properties of these fields are studied against the various parameters of the problem.

THE ELECTROMAGNETIC FIELD AT THE FLAT SURFACE OF CONDUCTING BODY CAUSED BY BASIC SOURCES OF A NON-UNIFORM EXTERNAL FIELD

The purpose of the work is to obtain the expressions for the intensities of the electric and magnetic components of electromagnetic field at the action of two types of the basic sources of external field located near conducting half-space, where the eddy currents flow. The basic sources are the rectilinear current of infinite length, parallel to the interface between the dielectric and conducting media, and the magnetic moment, oriented along normal to the interface. The solution for electromagnetic field at surface between the media is applied. It is valid for strong skin effect in the form of expansion into an asymptotic series. Each term of the series is proportional to the derivative of corresponding order of external field components. This allows taking into account the external field non-uniformity. It is shown that the mathematical models with ideal skin effect have limited application. Then it is necessary to use more correct mathematical models for non-uniform field and a bounded depth of skin layer. The obtained expressions for electromagnetic field at the action of the basic sources of non-uniform external field allow us to use the principle of superposition to determine the field distributions in electromagnetic systems with more complex three-dimensional configuration. References 25, figures 5.

Research note: A comparison between normalized controlled‐source electromagnetic field components and transfer functions as input data for three‐dimensional non‐linear conjugate gradient inversion

AbstractControlled‐source electromagnetic methods are applied to survey the electrical resistivity distribution of the subsurface. This work compares normalized electromagnetic field components and transfer functions such as impedance tensors and vertical magnetic transfer functions generated by two independent source polarizations as input data for three‐dimensional inversion. As most other available inversion codes allow for inverting only one of the mentioned input data types, it is unclear which data type is preferable for controlled‐source electromagnetic inversion. Our three‐dimensional non‐linear conjugate gradient inversion code can handle both input data types, facilitating a comparison of normalized electromagnetic field components and transfer functions inversion. Examining inversion results for a three‐dimensional synthetic model with two anomalies, we infer that the transfer functions inversion is favourable for recovering the overall resistivity distribution below the receiver sites in fewer iterations. The inversion of normalized electromagnetic field components produces a sharper image of the anomalies and may be capable of detecting the resistivity distribution below the extended sources, which comes at the price of introducing a more heterogeneous background resistivity in the model.

Subwavelength dielectric waveguide for efficient travelling-wave magnetic resonance imaging

Magnetic resonance imaging (MRI) has diverse applications in physics, biology, and medicine. Uniform excitation of nuclei spins through circular-polarized transverse magnetic component of electromagnetic field is vital for obtaining unbiased tissue contrasts. However, achieving this in the electrically large human body poses a significant challenge, especially at ultra-high fields (UHF) with increased working frequencies (≥297 MHz). Canonical volume resonators struggle to meet this challenge, while radiative excitation methods like travelling-wave (TW) show promise but often suffer from inadequate excitation efficiency. Here, we introduce a new technique using a subwavelength dielectric waveguide insert that enhances both efficiency and homogeneity at 7 T. Through TE11-to-TM11 mode conversion, power focusing, wave impedance matching, and phase velocity matching, we achieved a 114% improvement in TW efficiency and mitigated the center-brightening effect. This fundamental advancement in TW MRI through effective wave manipulation could promote the electromagnetic design of UHF MRI systems.

On-chip spatiotemporal optical vortex generation using an integrated metal–dielectric resonator

We theoretically demonstrate the possibility of generating a spatiotemporal optical vortex (STOV) beam in a dielectric slab waveguide. The STOV is generated upon reflection of a spatiotemporal optical pulse from an integrated metal–dielectric structure consisting of metal strips “buried” in the waveguide. For describing the interaction of the incident pulse with the integrated structure, we derive its “vectorial” spatiotemporal transfer function (TF) describing the transformation of the electromagnetic field components of the incident pulse. We show that if the TF of the structure corresponds to the TF of a spatiotemporal differentiator with a π/2 phase difference between the terms describing temporal and spatial differentiation, then the envelope of the reflected pulse will contain an STOV in all nonzero components of the electromagnetic field. The obtained theoretical results are in good agreement with the results of rigorous numerical simulation of the STOV generation using a three-strip metal–dielectric integrated structure. We believe that the presented results pave the way for the research and application of STOV beams in the on-chip geometry.

3D Polarisation of a Structured Laser Beam and Prospects for its Application to Charged Particle Acceleration

A Structured Laser Beam (SLB) is a type of optical beam with spatially inhomogeneous 3D polarisation structures. Generating SLBs from vector beams allows the creation of Hollow Structured Laser Beams (HSLB) with a dark central core. In this way, atypical electric and magnetic field vectors, which are purely longitudinally polarized in the dark zones of the beam, are obtained. The SLB spatial distribution can also include regions with both the electric and magnetic fields longitudinally polarized and oriented in the same or opposite directions. The SLB has a transverse distribution similar to that of a Bessel beam but can theoretically propagate to infinity, therefore giving the potential to generate strong, longitudinally oriented electric fields over long distances, which could possibly allow the acceleration of charged particles. The results of the study of this phenomenon, including simulations of the spatial distribution of the electromagnetic field components, are presented in this paper.

One-Dimensional Inverse Problem for Nonlinear Equations of Electrodynamics

For the system of nonlinear electrodynamics equations, we consider the problem of determining the medium conductivity coefficient multiplying the nonlinearity. It is assumed that the permittivity and permeability are constant and the conductivity depends only on one spatial variable, with this conductivity being zero on the half-line x . For a mode in which only two electromagnetic field components participate, the wave propagation process caused by the incidence of a plane wave with a constant amplitude from the domain x0 onto an inhomogeneity localized on the half-line x0 is considered. With a given conductivity coefficient, the conditions for the solvability of the direct problem and the properties of its solution are studied. To solve the inverse problem, the trace of the electrical component of the solution of the direct problem is specified on a finite segment of the axis x=0. A theorem on the local existence and uniqueness of the solution of the inverse problem is established, and a global estimate of the conditional stability of its solutions is found.

Computation of unsteady electromagnetic scattering about 3D complex bodies in free space with high-order difference potentials

We extend the previously developed high-order accurate method for acoustic scattering to electromagnetic scattering, i.e., from the scalar setting to a vector setting. First, the governing Maxwell's equations are reduced from their original first-order form to a system of second-order wave equations for the individual Cartesian components of electromagnetic field. In free space, these wave equations are uncoupled. Yet at the boundary of the scatterer, the variables that they govern (i.e., Cartesian field components) remain fully coupled via the boundary conditions that account for the specific scattering mechanism. Next, the wave equations are equivalently replaced with Calderon's boundary equations with projections obtained using the method of difference potentials and a compact high-order accurate scheme. The Calderon's boundary equations are combined with the boundary conditions and the overall system is solved by least squares. The resulting vector methodology (electromagnetic) inherits many useful properties of the scalar one (acoustic). In particular, it offers sub-linear computational complexity, does not require any special treatment of the artificial outer boundary, and has the capacity to solve multiple similar problems at a low individual cost per problem. We demonstrate the performance of the new method by computing the scattering of a given impinging wave about a double-cone hypersonic shape.

Feasibility of Tunnel TEM Advanced Prediction: A 3D Forward Modeling Study

The transient electromagnetic (TEM) method has long been applied in tunnel advanced prediction. However, it remains questionable to what extent a geologic anomaly body will influence the induced electromagnetic response in front of the heading face. The dilemma is partly because observed TEM data are frequently interpreted by empirical formulas or proportional relationships, and a quantitative measurement has not been established. In this paper, we strive to understand the TEM characteristics from a 3D finite-element time-domain (FETD) modeling aspect. The modeling algorithm is based on unstructured space meshing and unconditional stable time discretization, which ensures its accuracy and stability. The modeling algorithm is verified by a half-space model, in which the misfit of late-time channels that we are concerned with is generally below 1%. The algorithm has also been utilized to carry out the TEM response of tunnel models with different types of TEM devices. Through model studies, we find that both the traditional central-loop device and the recently developed weak-coupling opposing-coil device are feasible in tunnel advanced detection. Nevertheless, the latter type of device better distinguishes low-resistivity anomalies at 30 m ahead of the heading face with a relative difference (between models with and without the anomaly) of more than 1000% at certain time channels, compared with only a 10% difference of the central-loop device. Also, we conclude that the vertical electromagnetic field component should be recorded and interpreted together with the horizontal field to provide more convincing results.

METHODS AND MEANS OF INCREASING THE EFFICIENCY OF COMPOSITE MATERIALS FOR SHIELDING ELECTROMAGNETIC FIELDS

The main principles of increasing the shielding coefficients of electromagnetic fields by composite materials are considered. It is shown that the protective properties in the low-frequency and high-frequency regions of the electromagnetic spectrum are provided by different physical mechanisms. Therefore, to ensure acceptable protective properties, it is necessary to coordinate the ratio of electrophysical and magnetic properties of materials based on compromise solutions. The main condition in the process of designing materials is to take into account the strong frequency dependence of the dielectric and magnetic permeability of filler particles. To predict the required volume content of the shielding filler in the dielectric matrix, it is possible to use the Maxwell-Garnett, Odelevsky, and Lorentz formulas. At the same time, it should be taken into account that the differences between calculated and experimental results are at least 20 %. For simultaneous effective shielding of ultra-low-frequency and ultra-high-frequency electromagnetic fields, the material must have both sufficient magnetic properties and acceptable electrical conductivity. This can be achieved by treating the original mixture containing ferromagnetic particles with a constant magnetic field of 200–300 A/m. By arranging the arrangement of shielding particles in the body of the composite, conduction circles are formed. With a shielding material content of 12–16 % by volume, a percolation effect is achieved - a sharp increase in the electrical conductivity of the material and an increase in protective properties. The amount of filler depends not only on the total volume, but also on the size of individual particles. In this way, simultaneous shielding of both the magnetic component of the industrial frequency electromagnetic field and ultrahigh and higher frequency electromagnetic fields is achieved. It is shown that it is expedient to investigate the possibility of arranging non-magnetic particles in the body of the composite by treating the initial mixture with an electric field.

Non-equilibrium dynamics of dipole-charged fields in the Proca theory

We discuss the dynamics of field configurations encoded in the certain class of electric (magnetic) dipole-charged states in the Proca theory of the real massive vector field. We construct such states so as to ensure that the long-distance structure of the mean electromagnetic field in them is initially set by the formula describing the electromagnetic field of the electric (magnetic) dipole. We analyze then how such a mean electromagnetic field evolves in time. We find that far away from the center of the initial field configuration, the long-range component of the mean electromagnetic field harmonically oscillates, which leads to the phenomenon of the periodic oscillations of the electric (magnetic) dipole moment. We also find that near the center of the initial field configuration, the mean electromagnetic field escapes from its initial arrangement and a spherical shock wave propagating with the speed of light appears in the studied system. A curious configuration of the axisymmetric mean electric field is found to accompany the mean magnetic field in magnetic dipole-charged states.

Analysis and Application of the Electromagnetic Wave Propagation, Fields, and Dispersion Relation in an Elliptical Chiro Plasma Waveguide Immersed in Magnetized Plasma

AbstractThis research proposes and investigates an elliptical waveguide filled with chiro plasma as its core and magnetized plasma as its clad region. The clad region is in the constant infinite magnetic field, and its direction is the same as the wave propagation in the chiro plasma elliptical waveguide. The electromagnetic wave propagation in the considered waveguide is studied. The expressions for electromagnetic field components in the chiro plasma core and magnetized plasma cladding are derived. The dispersion relations for the hybrid modes are calculated considering appropriate boundary conditions at the chiro plasma and magnetized plasma interface. The behavior of the energy flux and the dispersion curves are numerically and graphically studied. It is seen that the magnitude of the power density decreases with the increase of the cyclotron frequency and it increases with the increase of the plasma frequency and supports power flow in the backward direction for the considered mode. Furthermore, it is shown higher values of the chirality parameter cause the magnitude of the power flux to increase in the backward direction.

Mechanism of action of the low-frequency electromagnetic field on aqueous solutions of biopolymers

This paper presents the mechanism of signal transformation by which a signal from the magnetic component of the low-frequency electromagnetic field with extremely low energy is changed into chemical and biochemical signals which elicit a biological response in aqueous solutions of biopolymers based on nucleic acids and proteins. A theoretical model developed shows that the basis of oxidative DNA damage and conformational transitions of proteins is a universal mechanism associated with a change in the amount of the most long-lived form - hydrogen peroxide in a chemical oscillator of mutual transformations of reactive oxygen species under the influence of low-intensity electromagnetic field exposure. It has been experimentally established that the quantitative content of hydrogen peroxide in solutions of biopolymers resonantly depends on the frequency of applied field. Conformational changes in proteins are accompanied by an increase in the availability and activity of the nucleophilic centers that are potential targets for reactive oxygen species. Complete unfolding and denaturation of the amino acid chain of the protein under the influence of low-frequency electromagnetic field exposure do not occur. It has been shown that enhanced hydrogen peroxide formation at 3 Hz and 50 Hz leads to oxidative modification of nitrogenous bases in DNA.

A matrix differential operator for passage from scalar to vector wave optics

One possible way to generalize scalar to wave optics, thus including polarization in the treatment consistent with the Maxwell equations was shown by Mukunda, Simon and Sudarshan (MSS) for paraxial systems, based on a group theoretical analysis. Later, the MSS theory for the passage from the Helmholtz scalar wave optics to the Maxwell vector wave optics was derived by casting the basic formalism in a framework very similar to the Dirac electron theory. Here, we show that the elegant MSS substitution rule is equivalent to a second-order 6 × 6 matrix differential operator for passage from scalar to vector wave optics. We explicitly obtained this matrix differential operator in a series and exponential forms respectively. Expressions for the electromagnetic field components are derived without making any assumptions on the form of the transverse beam profile. It is observed that all types of beams have certain characteristic relations among their field components. The power of the formalism is demonstrated by considering five specific beams.

Vectorial EM Propagation Governed by the 3D Stochastic Maxwell Vector Wave Equation in Stratified Layers

The modeling and processing of vectorial electromagnetic (EM) waves in inhomogeneous media are important problems in physics and engineering, and new methods need to be developed to incorporate novel vector sensor technology. Vectorial phenomena of EM waves in stratified atmospheric layers can be incorporated into governing equations by retaining the gradient of the refractive index when deriving the Maxwell Vector Wave Equation (MVWE) from Maxwell’s equations. The MVWE, as opposed to the scalar wave, Helmholtz, and paraxial equations, couples the EM field components in inhomogeneous media and thus captures important physics phenomena such as depolarization. Here, recent developments are reviewed on using sensor time series data to reconstruct electromagnetic waves that propagate through stratified media. In modern applications, often many sensors can be deployed simultaneously to observe electromagnetic waves. These networks of sensors can be used to improve the quality of the reconstructed EM wave fields and cross-validate the observed sensor time series. Lastly, the effects of noisy current densities on sensor time series are considered. Generally, as the sensor observes for longer periods of time, the variance of estimates of the wave field obtained from sensor time series data increases. As a result, longer sensor observation times do not always result in better estimates of the EM wave fields, and an optimal observation time can be obtained.

ASSESSMENT OF THE ADEQUACY OF COMPUTER SIMULATION OF THE ELECTROMAGNETIC ENVIRONMENT USING FREE SOFTWARE

Computer simulation of the electromagnetic environment makes it possible to determine the sources of the electromagnetic field and radiation at the object under study, accelerates the process of determining the degree of danger of the electromagnetic environment, forms pictures of the distribution in space of the components of the electromagnetic field and creates maps of the permissible time of human stay. Free software (openEMS, MEEP) significantly simplifies the solution of these tasks. The article considers the issues of assessing the adequacy of computer models of the distribution of electromagnetic field components formed using these modeling packages. The results of experimental measurements and computer simulation of the electric field at frequencies of 50 Hz, 30 kHz, 3 MHz, 30 MHz and 50 MHz are presented. The results of measurements and computer simulation of the electromagnetic field at frequencies of 800 MHz, 25 Khz and 40 GHz are presented. The adequacy of modeling the components of the electromagnetic field using openEMS and MEEP, sufficient for practical application, has been confirmed.

Methodological Foundations Protective Structures Development for Shielding Electromagnetic and Acoustic Fields

In many cases the simultaneous protection against electromagnetic and acoustic fields of wide frequency ranges is required. The complexity of such a task lies in the impossibility of significantly reducing low-frequency sound levels with traditional sound-absorbing materials, as well as the different requirements for materials that shield low-frequency and high-frequency electromagnetic fields. It is proposed to solve this problem by creating a two-layer structure, the front surface of which is solid, and the inner surface is perforated. The front panel can be made of non-conductive material. It is a variant of the Bekeshi panel and is mainly intended to reduce the level of low-frequency sound of a certain frequency with high amplitude. The perforation of the internal (metal) panel is chosen based on the need to provide shielding of electromagnetic and acoustic fields of certain frequencies or frequency bands. A calculator is provided for calculating the required panel parameters (linear dimensions, thickness, hole diameters, their number per unit of surface area). It is advisable to fill the space between the panels with a sound-absorbing material, for example, granulated polystyrene. It provides sound absorption of medium and high frequencies and makes the design broadband. The use of ferromagnetic material of the inner panel provides protection against the magnetic component of the ultra-low frequency electromagnetic field (mainly industrial). The perforation of the panel is calculated based on the waveguide theory of high-frequency electromagnetic waves. The results of tests of the effectiveness of facing metal-polymer material in the form of tiles are presented. The performance of the material is satisfactory for most industrial and domestic conditions. Determination of the mechanical properties of the material (Young's modulus, shear modulus and Poisson's ratio) showed that it is not inferior to known materials even with a large content of shielding substance. In order to rationalize the design of the structure, a priority factor and frequency (frequency band) is selected on the basis of live measurements of the electromagnetic and acoustic spectra. It is shown that the calculations have large volumes, and the solution of two-factor optimization problems is not always possible. Appropriate creation of application software to simplify the process of designing protective structures and rationalizing panel parameters based on the principles of reasonable sufficiency.

Electromagnetic field theory in superluminal spacetime

Recently, a number of experimental observations on the superluminal group velocities of pulses propagating in dispersive media have led to reconsidering electromagnetism theory in an unconventional framework. To consider faster-than-light phenomena, it is not necessary to replace the current relativistic theory, but it is sufficient to extend it to superluminal motions in a way that preserves the principle of causality. In the present paper, a new approach to study superluminal motions is proposed, which avoids introducing unphysical complex quantities and allows for the formulation of equations that are covariant according to a hyperbolic metric. In the framework of this formalism, Maxwell equations and the single-photon wave equation are obtained through superluminal transformations of ordinary equations. It is shown that the covariant and contravariant components of the superluminal electromagnetic field determine its magnitude and direction, respectively. Furthermore, the solutions of the transformed Maxwell equations are X-shaped ways propagating in the superluminal spacetime region that is delimited by the infinite light cone and the two-sheeted hyperboloid perpendicular to it. Instead, in quantum mechanics, the covariant and contravariant components of the electromagnetic field are proportional to the right- and left-handed helicities of the single photon, respectively.

Enhancement of the microwave photon-magnon coupling strength for a planar fabricated resonator

Planar resonators have a wide usage in modern microwave technologies and perspectives in novel quantum technologies development. As was demonstrated earlier, their utilization allows to achieve high values of microwave photon-magnon coupling strength—an important parameter in technologies of information coherent transfer from electromagnetic GHz range to the optical range. In the present work, the achievement of the high value of the microwave photon-magnon coupling strength by exploiting the increase of the spatial concentration of the magnetic component of the planar resonator electromagnetic field is reported. Starting from the conventional planar split-ring resonator design we increased the coupling strength up to 40% by modifying the resonator shape. The numerical simulation and experimental verification showed a predicted increase in the spatial concentration of the microwave magnetic component and showed the increased value of the microwave photon-magnon coupling strength as a sequence.

New approach to monitoring and characterizing the directionality of electromagnetic radiation generated from rock fractures

Electromagnetic radiation (EMR) is a common phenomenon widely used in engineering and geology fields for detection and monitoring. Although there are some attempts to monitor the directionality of electromagnetic radiation, they are limited by the inability to perform multi-directional measurements at the same time. As a result, the directionality of electromagnetic radiation induced by rock fracture is less involved. Here, four symmetrical three-axis antennas are used to monitor the fracture-induced electromagnetic radiation signals and characterize directionality during uniaxial compression experiments of limestone and granite. The synthesized signals of the four antennas are obtained based on the principle of vector synthesis. Signals monitored on the three axes differ significantly with the direction as the three electromagnetic field components are at the same position. The resultant vectors at the maximum intensities and the equivalent vectors calculated by energy ratio are used to characterize the directionality of electromagnetic radiation caused by fractures. The direction of those vectors shows an obvious correlation with the crack surface. Based on the above research, a new approach using electromagnetic radiation directionality to monitor the stress state and failure in engineering and geological sites is established.