Electric Field Components Research Articles

Accurate Time-Domain Modeling of Arbitrarily Shaped Graphene Layers Utilizing Unstructured Triangular Grids

The accurate modeling of curved graphene layers for time-domain electromagnetic simulations is discussed in the present work. Initially, the advanced properties of graphene are presented, focusing on the propagation of strongly confined surface plasmon polariton waves at the far-infrared regime. Then, the implementation of an unstructured triangular grid was examined, based on the Delaunay triangulation method. The electric-field components were placed at the edges of the triangles, while two different techniques were proposed for the sampling of the magnetic ones. Specifically, the first one suggests that the magnetic component is placed at the triangle’s circumcenter providing more accurate results, although instability may occur for nonacute triangles. On the other hand, the magnetic field was sampled at the triangle’s centroid, considering the second technique, ensuring the algorithm’s stability, but further approximations were required, leading to a slight accuracy reduction. Moreover, the updating equations in the time-domain were extracted via an appropriate approximation of Maxwell equations in their integral form. Finally, graphene was introduced in the computational domain as an equivalent surface current density, whose location matches the corresponding electric components. The validity of our methodology was successfully performed via the comparison of graphene surface wave propagation properties to their theoretical values, whereas the global error determination indicates the minimal triangle dimensions. Additionally, an instructive setup comprising a circular graphene scatterer was analyzed thoroughly, to reveal our technique’s advantages compared to the conventional staircase discretization.

Nonreciprocal and Non-Hermitian Material Response Inspired by Semiconductor Transistors.

Here, inspired by the operation of conventional semiconductor transistors, we introduce a novel class of bulk materials with nonreciprocal and non-Hermitian electromagnetic response. Our analysis shows that material nonlinearities combined with a static electric bias may lead to a linearized permittivity tensor that lacks the Hermitian and transpose symmetries. Remarkably, the material can either dissipate or generate energy, depending on the relative phase of the electric field components. We introduce a simple design for an electromagnetic isolator based on an idealized "MOSFET-metamaterial" and show that its performance can in principle surpass conventional Faraday isolators due to the material gain. Furthermore, it is suggested that analogous material responses may be engineered in natural media in nonequilibrium situations. Our solution determines an entirely novel paradigm to break the electromagnetic reciprocity in a bulk nonlinear material using a static electric bias.

Reflection Characteristics of Airy Beams Impinging on Graphene-Substrate Surfaces

In this work, we analytically and numerically investigate the reflection characteristics of the airy beams impinging on graphene-substrate surfaces. The explicit analytical expressions for the electric and magnetic field components of the airy beams reflected from a graphene-substrate interface are derived. The local-field amplitude, Poynting vector, and spin and orbital angular momentum of the reflected airy beams with different graphene structure and beam parameters are presented and discussed. The results show that the reflection properties of the airy beams can be flexibly tuned by modulating the Fermi energy of the graphene and have a strong dependence on the incident angle and polarization state. These results may have potential applications in the modulation of airy beams and precise measurement of graphene structure parameters.

Lower hybrid drift wave motion at a dayside magnetopause x-line with energy conversion dominated by a parallel electric field

On December 4, 2017 at approximately 6:15:38 UTC, magnetospheric multiscale (MMS) encountered a reconnecting current sheet near the dayside magnetopause. MMS2 passed through the current sheet just sunward of the southward-moving x-line and observed the crescent-shaped electron velocity distributions associated with reconnection. Additionally, MMS2 observed anti-correlated oscillations in the Hall electric field EN and in the parallel electric field Eǁ at a frequency just below the lower hybrid (LH) frequency. These oscillations appear to be LH drift waves (also called corrugations), which have previously been observed along the dayside magnetopause but were not seen to cause the same kinds of oscillations in the electric field components as observed in this event. It appears that MMS2 periodically crosses a separatrix between the region where EN dominates and a different region where Eǁ dominates at the wave frequency likely due to the wave motion. We also observe energy conversion dominated by Eǁ and veǁ, mostly in the L-direction, in this region as opposed to the reconnection electric field EM and meandering electrons moving in the M-direction as is typically observed during reconnection near an x-line.

Anomaly Detection of Pipeline Leakage Based on Electric Field Component Imaging Using Ground Penetrating Radar

Ground penetrating radar (GPR) is an effective method that can be applied in pipeline leakage detection. However, when the distribution of the underground medium is complex, it becomes difficult to accurately identify the abnormal leakage area directly from the GPR data profile. In this paper, based on the characteristics of high water content in the abnormal leakage area and according to the relationship between the reflected wave coefficient and the dielectric constant, the electric field component imaging technology of GPR data is proposed. Next, the electromagnetic wave responses of geological models with different dielectric parameters are simulated by finite difference time domain (FDTD). It can be seen from the forward modeling results that the greater the difference is in the dielectric constants of the media on both sides of the interface, the stronger the reflected wave energy will be. Finally, the electric field component imaging technology of GPR data is applied to pipeline leakage detection in an industrial area. The test results show that the abnormal area of pipeline leakage appears as a high‐amplitude area in the electric field component map.

Holographic detection of pulsed terahertz waves in terahertz time-domain spectroscopy

In the study of the interaction of terahertz (THz) wave with material, the traditional THz time-domain spectroscopy (THz-TDS) usually only detects the changes in amplitude and phase information of pulsed THz in a certain polarization direction before and after the interaction with the sample to be tested. However, in the detection of material such as anisotropic material and chiral material, only the amplitude and phase information of the sample cannot give the complete internal structure of the sample material. Anisotropic material and chiral material are very sensitive to pulsed THz of different polarization states. In order to reflect the configurations and conformations of these chiral substances through THz spectrum, it is necessary to detect the amplitude, phase and polarization state of the sample before and after pulse THz waves. The pulsed terahertz holographic detector (PTHD) in this work is composed of photoconductive antenna elements that are perpendicular to each other. The quadrature component of the pulsed THz electric field in any direction can be detected by one-time scanning, so that the changes in amplitude, phase and polarization state before and after the pulsed THz wave acts on the sample can be detected at the same time, so it is called pulsed THz wave holographic detection. Both experiments and theoretical analyses verify the reliability of the PTHD for measuring the polarization state of pulsed THz waves. At the same time, the response matrix is used to analyze that the PTHD has good symmetry in a spectral range of 0.1–2.2 THz.

Analysis and Experimental Verification of the Peaking Capacitor’s Flashover Process in an EMP Simulator

The flashover process of the peaking capacitor in the electromagnetic pulse (EMP) simulator is studied based on theoretical analyses and experimental verification in this paper. There are deeper and denser ablation spots on the film surface near the inner core of the destroyed peaking capacitor, while the damage of the outer film is relatively slight, which indicates that the flashover current along the inner film is larger. Besides, the circuit simulation analyses show that the earlier the flashover occurs on the film of the peaking capacitor, the smaller the flashover current. The electric field on the non-conical surface of the capacitor is mainly occupied with normal component. Differently, for the conical surface, the electric field on the outer layer is dominated by the normal component and the parallel component is the main part on the inner layer. It is considered that the flashover on the conical surface originates from outer layers and develops gradually to the inner until the flashover penetrates through all layers. Furthermore, the images of flashover show that the flashover firstly occurs on the outermost layers and develops to the inner layers with the increase of the voltage. For such special structure of the peaking capacitor, the parallel component of electric field is more likely to facilitate the flashover under nanosecond pulse. These results may exhibit specific reference implication in the design of insulation for the peaking capacitor used in EMP simulator.

Large Horizontal Near-Field Scanner Based on a Non-Tethered Unmanned Aerial Vehicle

A horizontal planar scanner with an approximate size of 40 m <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times40$ </tex-math></inline-formula> m has been implemented using the Unmanned Aerial Vehicle (UAV) technology. The UAV is not wired to the ground to maintain the flexibility and short setup time of a non-tethered flight. In this configuration, the UAV-mounted continuous-wave source is not phase-locked to the on-the-ground receiver. A dual-polarized reference antenna placed on the ground is hence used to retrieve the relevant phase information. The presented approach has been applied on the Pre - Aperture Array Verification System (Pre -AAVS1) of the Square Kilometre Array, which is a digital beamformed array with 16 active elements. An inverse source technique has been applied on measured Near-Field (NF) data acquired on two different sets of points (one for each electric field component) from all the receiver channels. In this way, Embedded Element Patterns (EEPs), array calibration coefficients and pattern have been determined from NF data only. The achieved results have been validated using a complementary set of Far-Field (FF) measurements and simulations.

ОПЕРАТОРНИЙ МЕТОД В ЗАДАЧІ ПРО ДИФРАКЦІЮ ПЛОСКОЇ ХВИЛІ НА НЕСКІНЧЕННО ТОНКИХ ІДЕАЛЬНО ПРОВІДНИХ НАПІВПЛОЩИНІ ТА ДВОХ ДИСКАХ

Subject and Purpose. Considered in the paper is diffraction of a plane wave by a structure involving a half-plane and two disks. The disks and the half-plane, lying within parallel planes, are assumed to be infinitely thin and perfectly conducting. The problem is to be analyzed for two cases, namely for that of both disks located on the same side with respect to the half-plane, and for the other where they are placed on opposite sides against the half-plane. The purpose of the paper is to develop a suitable operator method for performing the analysis of the structure described. Methods and Methodology. The solution to the problem has been sought for within the operator method suggested. The electric field components tangential to the half-plane and the disks are expressed, with the aid of Fourier integrals, via some unknown functions having the sense of amplitudes. The unknown amplitudes shall obey the operator equations formulated in terms of wave scattering operators for individual disks and the sole half-plane. Results. When subjected to certain transformations, the operator equations allow obtaining integral equations relative amplitudes of the spherical waves involved. The integral equations permit investigating scattered wave fields for the cases where the disks stay in the shadow region behind the half-plane or in the penumbra, or else in the region which is illuminated by the incident wave. As has been shown, in the case of plane wave scattering at the edge of the half-plane the resulting cylindrical waves possess non-zero amplitudes even with the disks placed totally in the shadow region, hence not illuminated by the incident plane wave. Conclusions. Making use of an operator method, an original solution has been obtained for the problem of plane wave diffraction by a structure consisting of a perfectly conducting, infinitely thin half-plane and two disks. The operator equations of the problem have been shown to be reducible to integral equations, further solvable numerically with the use of discretization based on quadrature rules. The behavior of far and near fields relative to the disks has been studied for a variety of values of the disk radii and their positions relative to the half-plane.

Graphene fibre film/polydimethylsiloxane nanocomposites for high-performance electromagnetic interference shielding.

Exploration of high-performance electromagnetic interference (EMI) shielding materials has become a trend to address the increasing electromagnetic (EM) wave pollution environment. In this paper, oriented graphene fibre film (GFF)/polydimethylsiloxane (PDMS) nanocomposites with one-ply unidirectional, two-ply cross-ply, and two-ply unidirectional configurations were prepared using wet-spinning and hot-pressing techniques in a two-step process. Due to the anisotropic electrical performance of GFF, the one-ply laminate exhibits EMI shielding anisotropy that is affected by fibre orientation relative to the electric field component in EM waves. The maximum shielding difference at 8.8 GHz is up to 32.0 dB between the fibre orientation parallel to and perpendicular to the electric field component. In addition, we found that adding a layer of GFF is an intuitive method to enhance the shielding efficiency (SE) of GFF/PDMS nanocomposites by providing more interfaces to enhance absorption losses. An optimal EMI shielding performance of a two-ply unidirectional laminate is observed with an SE value of 50.6 dB, which shields 99.999% of EM waves. The shielding mechanisms are also discussed and clarified from the results of both experimental and theoretical analyses by adjusting the GFF structural parameters, such as the fibre orientation, areal density, number of plies and stacking sequence.

A Decoupled Calibration Method Based on the Multi-Output Support Vector Regression Algorithm for Three-Dimensional Electric-Field Sensors.

Aiming at the problem that the measured accuracy of the electric field intensity which is affected by the coupling interference by sensor output signal from the component of a three dimensional electric field, the causes of the coupling error was analyzed, and a decoupled calibration method based on support vector regression algorithm for three-dimensional electric field sensor is proposed. The solution of the decoupled calibration matrix was regarded as a multi-objective optimization process, and the optimal decoupling calibration matrix was obtained by the ν-SVR algorithm. The complex inverse calculation of the matrix was avoided, and the calculation error was reduced. A rotary calibration device was designed to accurately measure the angle between the induction electrode of the sensor and the electric-field vector, and an accurate calculation model of the theoretical electric field was established. The experimental results showed that the error between the calculated and theoretical values of the electric-field components obtained by the proposed method were smaller than those obtained by the traditional inverse matrix calibration method, the accuracy of the calibration was improved, the rationality of the calibration method was proven, and the accuracy of the three-dimensional electric-field intensity measurements was further improved.

3D non-driven magnetic reconnection at multiple separators

Separators are important topological features of magnetic configuration for magnetic reconnection, commonly found in the solar plasma. They are located at the boundary shared among four distinctive flux domains; therefore, current layers easily build up around them. This paper aims to explore non-driven magnetic reconnection at multiple separators since little information is available about it. We have done two sets of experiments: non-resistive magnetohydrodynamic (MHD) relaxation and resistive MHD reconnection of a magnetic configuration consisting of two null points alongside their associated spines and three non-potential separators, which connect the same two null points. We used the LARE3D code for this purpose. The main current layers are formed along these separators where reconnection takes place. The reconnection occurs in two distinct phases: fast–strong and slow–weak. Most of the current dissipates at a fast rate, through Ohmic heating, during the fast–strong phase. The short-lived impulsive bursty reconnection events occur randomly in the slow–weak phase, while viscous heating exceeds Ohmic heating in this phase. The electric field component is parallel to field lines along the separators; likewise, the rate of reconnection along each of them evolved over time. However, work on separator reconnection has a strong potential to understand the underlying physics.

Role of Parallel Solenoidal Electric Field on Energy Conversion in 2.5D Decaying Turbulence with a Guide Magnetic Field

Abstract We perform 2.5D particle-in-cell simulations of decaying turbulence in the presence of a guide (out-of-plane) background magnetic field. The fluctuating magnetic field initially consists of Fourier modes at low wavenumbers (long wavelengths). With time, the electromagnetic energy is converted to plasma kinetic energy (bulk flow+thermal energy) at the rate per unit volume of J · E for current density J and electric field E . Such decaying turbulence is well known to evolve toward a state with strongly intermittent plasma current. Here we decompose the electric field into components that are irrotational, E ir, and solenoidal (divergence-free), E so. E ir is associated with charge separation, and J · E ir is a rate of energy transfer between ions and electrons with little net change in plasma kinetic energy. Therefore, the net rate of conversion of electromagnetic energy to plasma kinetic energy is strongly dominated by J · E so, and for a strong guide magnetic field, this mainly involves the component E so,∥ parallel to the total magnetic field B . We examine various indicators of the spatial distribution of the energy transfer rate J ∥ · E so,∥, which relates to magnetic reconnection, the best of which are (1) the ratio of the out-of-plane electric field to the in-plane magnetic field, (2) the out-of-plane component of the nonideal electric field, and (3) the magnitude of the estimate of current helicity

Effects of gas adsorbed on solid surface during gas breakdown in electron cyclotron resonance discharges

The microwave breakdown power (P wb) in an ECR plasma source was not merely determined by pressure (gas flow rate), but found to vary with the time interval between two successive breakdowns. The measured P wb dropped rapidly from a high value at a short time interval to a low level at a long time interval. The obtained dependence of P wb on pressure (gas flow rate) exhibited distinct features: the normal monotonicity and abnormal non-monotonicity at the short and long time intervals, respectively. The effective zone in the antenna’s surface, bombarded by hot electrons heated in the ECR layer, was validated by (1) masking the antenna with a film having a variable radius; (2) calculating the distribution of the vertical component of the microwave electric field with respect to the static magnetic field; and (3) imaging glows of transient breakdown discharges with a fast camera. The reduction in P wb was mainly attributed to the enhanced emission of δ-electrons from the gas-adsorbed antenna under the bombardment of energetic electrons coming from the ECR layer. The correlation between the dynamic gas coverage and the emission coefficient of δ-electrons was established to understand the abnormal ECR breakdown features.

Ground-based measurements of microwave brightness temperature and electric field fluctuations for clouds with a different level of electrical activity

Simultaneous measurements of the brightness temperature and short-period electric field fluctuations were carried out to reveal possible connections between the electrification rate and turbulence intensity in clouds. The measurements were conducted in Nizhny Novgorod, Russia (56°19′37″N 44°00′27″E) in 2013 and 2018. The 8 mm radiometer was used to measure the brightness temperature of thermal radiation, and the vertical component of the atmospheric electric field were carried out using an electrostatic fluxmeter. With the use of meteorological data and electric field measurements the state of analyzed events has been classified into 4 types: cloudless atmosphere and high-level clouds (Cs), cumulus clouds (Cu), cumulonimbus clouds without lightning that cause strong electrical field disturbances near the ground surface (Cb), cumulonimbus thunderstorm clouds with lightning discharges (Cb+). Detailed statistical characteristics of brightness temperature fluctuations and short-period electric field fluctuations are obtained for the first time for the indicated types of events.It is shown that measured spectral densities of the atmosphere brightness temperature and electric field fluctuations correspond well enough in the considered frequency range to the results of presented theoretical consideration. Precipitation particles in clouds can be considered herewith as passive scalar, and the movement of inhomogeneities in the particle density can be described by Kolmogorov theory. Since electric charges are located on the precipitation with small droplet and ice particles, an increase in the inhomogeneities of the water content means likely an increase in the inhomogeneities of the electric charge. For thunderclouds the estimates of the relative fluctuations of liquid water content give values of the order of tens of percent. There is a tendency towards a relative increase in brightness temperature fluctuations at high frequencies in the band around f ≈ 10−2 Hz (and possibly higher than fmax ≈ 0.05 Hz) for the sequence of cloud types Cu, Cb, Cb+.

Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands

In this article we aim to investigate the kinetic turbulence in a reconnecting current sheet (RCS) with X- and O-nullpoints and to explore its link to the features of accelerated particles. We carry out simulations of magnetic reconnection in a thin current sheet with 3D magnetic field topology affected by tearing instability until the formation of two large magnetic islands using particle-in-cell (PIC) approach. The model utilizes a strong guiding field that leads to the separation of the particles of opposite charges, the generation of a strong polarization electric field across the RCS, and suppression of kink instability in the “out-of-plane” direction. The accelerated particles of the same charge entering an RCS from the opposite edges are shown accelerated to different energies forming the “bump-in-tail” velocity distributions that, in turn, can generate plasma turbulence in different locations. The turbulence-generated waves produced by either electron or proton beams can be identified from the energy spectra of electromagnetic field fluctuations in the phase and frequency domains. From the phase space analysis we gather that the kinetic turbulence may be generated by accelerated particle beams, which are later found to evolve into a phase-space hole indicating the beam breakage. This happens at some distance from the particle entrance into an RCS, e.g. about 7di (ion inertial depth) for the electron beam and 12di for the proton beam. In a wavenumber space the spectral index of the power spectrum of the turbulent magnetic field near the ion inertial length is found to be −2.7 that is consistent with other estimations. The collective turbulence power spectra are consistent with the high-frequency fluctuations of perpendicular electric field, or upper hybrid waves, to occur in a vicinity of X-nullpoints, where the Langmuir (LW) can be generated by accelerated electrons with high growth rates, while further from X-nullponts or on the edges of magnetic islands, where electrons become ejected and start moving across the magnetic field lines, Bernstein waves can be generated. The frequency spectra of high- and low-frequency waves are explored in the kinetic turbulence in the parallel and perpendicular directions to the local magnetic field, showing noticeable lower hybrid turbulence occurring between the electron’s gyro- and plasma frequencies seen also in the wavelet spectra. Fluctuation of the perpendicular electric field component of turbulence can be consistent with the oblique whistler waves generated on the ambient density fluctuations by intense electron beams. This study brings attention to a key role of particle acceleration in generation kinetic turbulence inside current sheets.

Electrodynamic Contributions to the Hall‐ and Parallel Electric Fields in Collisionless Magnetic Reconnection

AbstractIn collisionless magnetic reconnection, the Hall electric field and the parallel electric field play important roles because they are responsible for acceleration of charged particles, especially electrons. Using particle‐in‐cell simulations, we study electrodynamic nature of the two electric fields in two‐dimensional collisionless reconnection. We find that the Hall electric field is predominantly () electrostatic; its electromagnetic (induced) component is small but nonzero (). The parallel electric field or potential is contributed comparably by its electrostatic and induced components. In the electron inflow region, along the separatrix, and at the X‐line, the electrostatic component of the parallel electric field (or potential) is larger; while in the electron outflow region, the electromagnetic (induced) component is larger. An initial guide field does not change the electrodynamic nature of the Hall electric field but does change that of the parallel electric field. In the guide field case, the parallel electric field is contributed predominantly by the electromagnetic component from the electron inflow region to the X‐line and by the electrostatic component in the electron outflow region.

Fermi acceleration in relativistic collisionless plasma shocks correlates with anisotropic energy gains

Collisionless shocks generated by two colliding relativistic electron-positron plasma shells are studied using particle-in-cell simulations. Shocks are mediated by the Weibel instability (WI), and the kinetic energy of the fastest accelerated particles is found to be anisotropically modified by WI-induced electric fields. Specifically, we show that all particles interacting with the shock bifurcate into two groups based on their final relativistic Lorentz factor γ: slow (γ&amp;lt;γbf) and fast (γ&amp;gt;γbf), where γbf is the bifurcation Lorentz factor that was found to be approximately twice the initial (upstream) Lorentz factor γ0. We have found that the kinetic energies of the slow particles are equally affected by the longitudinal and transverse components of the shock electric field, whereas the fast particles are primarily accelerated by the transverse field component.

The properties of mid infrared surface modes at the interface of air and one dimensional ternary photonic crystal

In the present manuscript, theoretical design of truncated one dimensional ternary photonic crystal is proposed for analyzing the properties of transverse electric (TE) surface modes viz. band structures, its localization in photonic band gaps (PBGs), field profiles and energy carried by these modes. The periodicity of the structure (comparable to the wavelength of incident electromagnetic waves) is chosen as such the modes are localized in mid-infrared frequency domain (600cm−1 to 1800cm−1 or 5μm to 16μm). The dispersion relation of surface modes is derived by using continuity condition of tangential components of electric and magnetic fields and transfer matrix method. It is found that by varying the cap layer thicknessdc and thickness of first layerdt of each unit cell, surface modes are either strongly (near center of PBG with decay length ~8.8μm) or weakly (near edge of PBG with decay length ~42.5μm) bounded to the interface. The energy carried by the surface modes along the interface plane is around 3.3mJ while across the interface plane it is of the order of10−14. It has been proved that the material rich modes (~2V/m) have high field enhancement compared to material deficient modes (~1V/m). The study stresses on different aspects of the proposed model that can be sought for suitable practicable applications in mid-infrared photonics, especially in design of mid-infrared bio-chemical sensors, mid-infrared temperature sensors, waveguides, omnidirectional reflectors, optical filters, band edge lasers, multiplexers, mitigators, compensators, etc.

Analysis of non-idealities in rhomb compensators.

In-line rotatable rhombs that are only weakly chromatic are desired as compensators for a wide variety of applications in spectroscopic polarimetry and Mueller matrix spectroscopic ellipsometry. These devices employ multiple total internal reflections to generate differences in the phase shifts upon reflection for orthogonal fast and slow axis optical electric field components. A framework has been developed for characterization of non-idealities in the performance of rhombs due to dissipation and associated dichroism upon each reflection as well as stress-induced birefringence along each beam path. External oblique reflection measurements by spectroscopic ellipsometry for the internally reflecting interface structures has enabled characterization of the dichroic effects and retardance generated by the reflections. The framework for analysis of the effects of stress relies on simulations demonstrating that the contributions to polarization modification from each beam path depend only on the accumulated stress-induced retardance and average azimuthal angle of the fast principal stress axis along the given path. The overall approach has been applied to straight-through Mueller matrix measurements of a three-reflection rhomb in its operational configuration to establish the set of stress parameters for each of the four beam paths needed to fit the measurements. Thus, device geometry and optical structure, including layer thicknesses and component media optical properties, as well as stress-induced retardances and average stress azimuthal angles, which are all deduced in the analysis, enable a complete description of the polarization modifying properties of the rhomb when serving as a compensator.