Horizontal Electric Field Components Research Articles

A stable analytical expression for magnetotelluric/radiomagnetotelluric impedances in anisotropic layered Earth models

Previous closed-form solutions of impedances on layered Earth models were only available for the anisotropic conductivity case under the plane wave electromagnetic incidence. Here, we have developed a numerically stable impedance formula for both magnetotelluric and radiomagnetotelluric problems in layered media with arbitrarily anisotropic conductivity and dielect permittivity. Maxwell equations are first transformed into a set of coupled second-order partial differential equations with the horizontal components of electric field as the variables. Then, the recursive formula of surface impedance is obtained by using the general solutions of the second-order partial differential equations and the tangential continuity condition of electromagnetic fields at each layer interface. To avoid the numerical overflow in both the nominator and denominator of the recursive impedance formula due to large layer thickness or high working frequency, an artificial exponential function with positive exponential factor is used to regularize both the nominator and denominator. It leads numerically stable recursive formula for any layer thickness and working frequency. At the end, a four layered magnetotelluric model with anisotropic conductivities is adopted to validate the newly derived analytical formula and another two synthetic layered Earth models are used to study the effects of conductive anisotropy and dielectric anisotropy on radiomagnetotelluric responses.

New Concept Ocean-Bottom Multiphysics (OBMP) Nodes for Reservoir Monitoring

Marine-controlled source electromagnetics (CSEM) have been extensively applied to various exploration scenarios worldwide. However, its perceived value and cost relative to seismic and the scarcity of realistic case studies have limited the industry’s interest in time-lapse reservoir-monitoring (4D) applications. A feasible way to make demand for CSEM for 4D-monitoring programs would be to increase the value of information and reduce survey costs by performing joint operations where seismic and CSEM data are acquired during the same survey and at equivalent spatial densities. To this end, we propose a new multiphysics ocean-bottom nodes (OBN) concept and show the industry that CSEM can be a cost efficient and effective integrators to 4D seismic projects. To this end, we conducted a feasibility study demonstrating that horizontal magnetic field components have the required sensitivities and can be used instead of horizontal electric field components in mapping the 3D resistivity distribution and 4D fluid change responses in a given reservoir. This makes engineering a new OBN class simpler and cheaper, as various miniaturized magnetic field sensors are available off-the-shelf or readily working along with packaging and coupling solutions.

New Insights into the Anomaly Genesis of the Frequency Selection Method: Supported by Numerical Modeling and Case Studies

The frequency selection method (FSM) is the further development of the audio frequency telluric electricity method (TEFM). However, debate continues regarding the mechanisms leading to anomaly genesis. Therefore, the present study intends to explore this using 2D forward modeling of magnetotelluric (MT) sounding and practical applications of FSM on three Chinese case studies in karst and granitic settings. In the first stage, the profile curves and pseudo-section of apparent resistivity ( $${\rho }_{s}$$ ) and horizontal electric field component $${(E}_{y})$$ in MT mode are obtained by forward calculation. As a result, the static shift in $${\rho }_{s}$$ is observed over the near-surface inhomogeneities, as documented in the literature. Additionally, the profile curves of $${E}_{y}$$ showed an obvious static shift in the rectangular coordinate system (i.e., the curve rises with the increase in frequency) which is a well-known phenomenon. The pseudo-sections of $${E}_{y}$$ also showed static shift characteristics at the horizontal position above the anomaly, referred to as the “noodles phenomenon.” The FSM results were obtained from case studies related to groundwater and low-resistivity clay-filled karst body identification. The $$\Delta V$$ section curves and pseudo-section showed a significant low potential, and a “noodles phenomenon,” respectively, above the low-resistivity anomalous body. These abnormal characteristics of $$\Delta V$$ are the basis for delineating the horizontal position of the groundwater aquifer by applying FSM. It is concluded that the anomaly of FSM is the reflection of the static shift in MT, and hence, the FSM can be categorized as a “static shift method.” Therefore, this inspired us to investigate whether the static shift feature of the surface $${E}_{y}$$ component could be utilized to explore near-surface geological bodies such as clay-filled or water-filled cavities.

Wideband and metal‐only linear to circular polarization converter using multi‐slot elements

A wideband, metal-only, and low-cost transmission-type polariser is proposed in which a plane wave with linear polarization impinging on the structure is converted to circular polarization wave on the other side and vice versa. The proposed structure is a quad-layer frequency selective surface that its unit cell is composed of two sets of multi-slot elements placed perpendicular to each other to achieve a wideband polariser. In this unit cell, by changing the length of the slots, the amplitude and phase of transmission coefficient can be controlled, which are used to create a 90-degree phase difference between vertical and horizontal components of the incident electric field. A 9 × 9 $9\times 9$ array of the proposed polariser with a quad-layer is simulated and fabricated that shows the bandwidth of 22% (11.7–14.7 GHz) for an axial ratio below −3 dB and a transmission efficiency of more than 85%.

The Whole-Space Modeling of the Hazardous Geological Body ahead of the Tunnel Face by the Transient Electromagnetic Method

Karst caves are widely distributed in southwest China, causing difficulties and disasters for tunnel construction. To better detect the krast caves in front of the tunnels under construction using the transient electromagnetic method, in this paper we propose a 3-D finite element method to simulate the multi-parameter transient electromagnetic response of unfavorable geological bodies in a whole-space. First, the models of vertical water-filled faults, water-filled caves and complex geological bodies in front of the tunnel face are established. The horizontal electric field component and the vertical magnetic field component at different time in the whole-space are researched. Secondly, the electromagnetic response features of the caves with different resistivity, buried depths and scales are studied. We found that the resistivity of the target body is 10 times larger than that of the surrounding rocks, and the anomaly amplitude increases obviously with the growing distance from the target body. The deeper the buried depth, the later the anomaly appears and the smaller the anomaly amplitude. The larger the target size, the longer the transient electromagnetic response delay and the larger the anomaly amplitude. We arranged a measuring line on the tunnel face. The full-time apparent resistivity section shows the position and characteristics of the low-resistivity anomalous body, indicating that the transient electromagnetic method (TEM) has obvious advantages in detecting the low-resistivity body in front of the tunnel face. Finally, the TEM is successfully applied to the advanced detection of a karst tunnel to get the electrical distribution of the surrounding rocks in front of the tunnel face. According to the geological conditions of the excavated tunnel, the validity of the TEM in the tunnel advanced prediction is verified.

Analysis of SEGR in Silicon Planar Gate Super-Junction Power MOSFETs

This article compares and analyzes the single-event gate rupture (SEGR) response of silicon planar gate super-junction (SJ) power metal oxide semiconductor field effect transistors (MOSFETs) and vertical double diffused power MOSFETs (VDMOSs). When an incident heavy-ion strike is perpendicular to the gate oxide, the SEGR tolerances of SJ power MOSFETs (SJMOSs) and VDMOSs are similar. But, for heavy-ion strikes that are at different angles, SJMOS has better SEGR tolerance than VDMOS. This improved performance of SJMOS is due to the presence of an additional horizontal electric field component in SJMOS devices. This is validated using the experimental data and simulation results in this article.

Dual Circularly Polarized Planar Four-Port MIMO Antenna with Wide Axial-Ratio Bandwidth.

A broadband compact-sized planar four-port multiple-input–multiple-output (MIMO) antenna with polarization diversity is presented. The proposed dual circularly polarized (CP) MIMO antenna consists of four G-shaped monopole elements, two of which are left-hand CP and the other two are right-hand CP. A vertical line strip in the G-shaped radiating element acts in balancing the vertical and horizontal electric field components to obtain 90° phase difference between them for circular polarization. Also, an I-shaped strip is incorporated between the ground planes of the G-shaped antenna elements to obtain equal voltage level in the proposed MIMO configuration. The dual circular polarization mechanism of the proposed MIMO/diversity antenna is analysed from the vector current distributions. The impedance bandwidth (S11 ≤ –10 dB) of the MIMO antenna is 105.9% (4–13 GHz) and the 3 dB axial ratio bandwidth (ARBW) is 67.7% (4.2–8.5 GHz), which is suitable for C-band applications. The overall size of the MIMO antenna is 70 × 68 × 1.6 mm3, and the minimum isolation between the resonating elements is 18 dB. The envelope correlation coefficient is less than 0.25, and the peak gain within the resonating band is 6.4 dBi.

All-optical orientation of linear molecules with combined linearly and elliptically polarized two-color laser fields.

We show that a combination of a fundamental pulse with linear polarization along the vertical direction and an elliptically polarized second harmonic pulse with both vertical and horizontal electric field components can be used to orient linear molecules efficiently, leading to higher degrees of orientation. Due to this specific combination of polarizations, the asymmetric hyperpolarizability interaction potential, which remains the same as that in a linearly polarized two-color laser field, is created along the vertical component of the elliptically polarized second harmonic pulse. On the other hand, the horizontal component suppresses the otherwise strong symmetric polarizability potential responsible for alignment, increasing the tunneling probability from the shallower potential well to the deeper one. As a result, the degree of orientation increases and can be controlled by changing the intensity of the horizontal component of the elliptically polarized second harmonic pulse. This study is the generalization of the all-optical molecular orientation technique based on the anisotropic hyperpolarizability interaction.

Compact Matrix Formulation for Calculating Lightning-Induced Voltages on Electromagnetic Transient Simulators

In this paper, a compact matrix formulation that simplifies the calculation of the lumped sources necessary to estimate lightning-induced effects using transmission line models available in electromagnetic transient programs is proposed. As opposed to an existing solution strategy that requires the sequential calculation of the convolution integrals involving the horizontal component of the incident electric field along multiple segments along the line, the proposed matrix solution allows such convolutions to be performed at once. This not only increases the model efficiency, but also simplifies the assembly of the solution in matrix-oriented simulation tools. The equations are described in both phase and modal domains, with formulations that are compatible with the universal line model and the frequency-dependent transmission line model proposed by Marti. It is shown that both formulations can be accurately used for calculating lightning-induced voltages on overhead lines.

All-Metal 3-D Frequency-Selective Surface With Versatile Dual-Band Polarization Conversion

A dual-band periodic structure is here proposed, which allows for versatile frequency selectivity and polarization conversion functionality. The structure is a monolithic full-metal piece, and it is built from the arrangement of unit cells consisting of waveguide sections at cutoff loaded with compound perforations. The topology of such unit cells enables the efficient and independent interaction with vertical and horizontal electric field components illuminating the periodic structure. A circuit model is proposed to characterize the cells and understand their behavior. Three different examples of cells are designed to illustrate the structure versatile functionality. One of these examples is manufactured, consisting of a dual-band structure that converts linear polarization into circular with orthogonal senses of rotation at each band. The experimental results are in good agreement with the theoretical predictions, thus validating the underlying operation mechanism and its practical feasibility.

Reflective blue phase liquid crystal display with triangular dielectric layer

ABSTRACT We propose a reflective blue-phase liquid-crystal display (LCD) with triangular dielectric layers and a diffuse reflector electrode. The triangular dielectric layers with a high dielectric coefficient on the top and bottom indium tin oxide glass substrates are equivalent to the conductive plates, forming a corrugated electrode structure. This type of reflective blue-phase LCD based on planar electrode and diffuse mirror electrode can offer relatively high reflectance (~74.5%) and low operation voltage (9.2 Vrms) compared to most other devices due to its fairly strong and uniform horizontal electric field component along the whole blue-phase liquid crystal bulk. This design has the advantages of fast response time, easy manufacturing process, a high resolution and full-colour capability. It is a promising future high-quality reflective full-colour microdisplay.

Algorithm for modeling electromagnetic channel of seismo-ionospheric coupling (SIC) and the variations in the electron concentration

We present in detail the algorithm of the electrostatic–quasi-stationary–electromagnetic/MHD approximations and equivalent external sources (EQUEMES method) to develop the quasi-stationary–electromagnetic models of seismo-ionospheric coupling. The penetration of the electromagnetic field created by near-Earth alternative currents of ULF range was simulated by solving equations for the horizontal electric field components Ex, Ey of the second order with respect to the vertical coordinate z. This system of two second-order equations is derived from the system of Maxwell equations. The penetration of rather strong horizontal electric field [of order of (1–10) mV/m] to the ionospheric E and F layers has been modeled. The corresponding variations in the electron concentration in the E and lower F layers of the ionosphere reach a value of order of (1–10)%. Farther increase in these variations can be connected with the related synergetic processes. A possibility of the effective initiation of electron concentration perturbations in the unstable near-equatorial plasma in the F layer of the ionosphere by the packet of atmospheric gravity waves radiated by the near-ground source is illustrated. A good correspondence of the results obtained on the basis of this model to the data of satellite observations is shown.

Elongated horizontal and vertical receivers in three‐dimensional electromagnetic modelling and inversion

ABSTRACTElectromagnetic geophysical methods often rely on measurements of naturally occurring or artificially impressed electric fields. It is technically impossible, however, to measure the electric field directly. Instead, the electric field is approximated by recording the voltage difference between two electrodes and dividing the obtained voltage by the distance between the electrodes. Typically, modelling and inversion algorithms assume that the electric fields are obtained over infinitely short point‐dipoles and thus measured fields are assigned to a single point between the electrodes. Such procedures imply several assumptions: (1) The electric field between the two electrodes is regarded as constant or being a potential field and (2) the receiver dimensions are negligible compared to the dimensions of the underlying modelling grid. While these conditions are often fulfilled for horizontal electric fields, borehole sensors for recordings of the vertical electric field have dimensions in the order of ≈100 m and span several modelling grid cells. Observations from such elongated borehole sensors can therefore only be interpreted properly if true receiver dimensions and variations of electrical conductivity along the receiver are considered. Here, we introduce a numerical solution to include the true receiver geometry into electromagnetic modelling schemes, which does not rely on such simplifying assumptions. The algorithm is flexible, independent of the chosen numerical method to solve Maxwell's equations and can easily be implemented in other electromagnetic modelling and inversion codes. We present conceptual modelling results for land‐based controlled source electromagnetic scenarios and discuss consideration of true receiver geometries for a series of examples of horizontal and vertical electric field measurements. Comparison with Ez data measured in an observation borehole in a producing oil field shows the importance of both considering the true length of the receiver and also its orientation. We show that misalignment from the vertical axis as small as 0.1° may seriously distort the measured signal, as horizontal electric field components are mapped into the desired vertical component. Adequate inclusion of elongated receivers in modelling and inversion can also help reducing effects of static shift when interpreting (natural source) magnetotelluric data.

Lunar surface potential and electric field**A contributed paper from the International Symposium on Lunar and Planetary Science (ISLPS) on 2018 June 12–15 at Macau University of Science and Technology.

The Moon has no significant atmosphere, thus its surface is exposed to solar ultraviolet radiation and the solar wind. Photoemission and collection of the solar wind electrons and ions may result in lunar surface charging. On the dayside, the surface potential is mainly determined by photoelectrons, modulated by the solar wind; while the nightside surface potential is a function of the plasma distribution in the lunar wake. Taking the plasma observations in the lunar environment as inputs, the global potential distribution is calculated according to the plasma sheath theory, assuming Maxwellian distributions for the surface emitted photoelectrons and the solar wind electrons. Results show that the lunar surface potential and sheath scale length change versus the solar zenith angle, which implies that the electric field has a horizontal component in addition to the vertical one. By differentiating the potential vertically and horizontally, we obtain the global electric field. It is found that the vertical electric field component is strongest at the subsolar point, which has a magnitude of 1 V m−1. The horizontal component is much weaker, and mainly appears near the terminator and on the nightside, with a magnitude of several mV m−1. The horizontal electric field component on the nightside is rotationally symmetric around the wake axis and is strongly determined by the plasma parameters in the lunar wake.

A possible mechanism of stimulation of seismic activity by ionizing radiation of solar flares

A possible mechanism of earthquake triggering by ionizing radiation of solar flares is considered. A theoretical model and results of numerical calculations of disturbance of electric field, electric current, and heat release in lithosphere associated with variation of ionosphere conductivity caused by absorption of ionizing radiation of solar flares are presented. A generation of geomagnetic field disturbances in a range of seconds/tens of seconds is possible as a result of large-scale perturbation of a conductivity of the bottom part of ionosphere in horizontal direction in the presence of external electric field. Amplitude-time characteristics of the geomagnetic disturbance depend upon a perturbation of integral conductivity of ionosphere. Depending on relation between integral Hall and Pedersen conductivities of disturbed ionosphere the oscillating and aperiodic modes of magnetic disturbances may be observed. For strong perturbations of the ionosphere conductivities amplitude of pulsations may obtain ~10² nT. In this case the amplitude of horizontal component of electric field on the Earth surface obtains 0.01 mV/m, electric current density in lithosphere –10^–6 A/m², and the power density of heat release produced by the generated current is 10^–7 W/m³. It is shown that the absorption of ionizing radiation of solar flares can result in variations of a density of telluric currents in seismogenic faults comparable with a current density generated in the Earth crust by artificial pulsed power systems (geophysical MHD generator " Pamir-2” and electric pulsed facility " ERGU-600”), which provide regional earthquake triggering and spatiotemporal variation of seismic activity. Therefore, triggering of seismic events is possible not only by man-made pulsed power sources but also by the solar flares. The obtained results may be a physical basis for a novel approach to solve the problem of short-term earthquake prediction based on electromagnetic triggering phenomena.

Inversion of a Thunderstorm Cloud Charging Model Based on a 3D Atmospheric Electric Field

The measurement of the atmospheric electric field is of great significance for the study of thunderstorm cloud charge models. Traditional electric field meters can only measure the vertical component of the atmospheric electric field, and thus it is difficult to invert the structure of the thunderstorm cloud. A three-dimensional atmospheric electric field meter was developed to simultaneously measure the horizontal and vertical components of the atmospheric electric field in this paper. The effective measurement linearly relates the measured electric field to the induced voltage, and the nonlinear equations of the three-dimensional atmospheric electric field and the thunderstorm cloud-charging model parameters were derived. The particle swarm optimization algorithm (PSO) and the three-dimensional atmospheric electric field were used to invert the thunderstorm clouds. Experimental observations of the three-dimensional electric field in a cloud during a thunderstorm were analyzed. Combined with the typical charged structure model, parameters such as the charge and relative distance of the thunderstorm cloud were determined. The results showed that the value of the inversion fitness function reached 0.7288, and the charge structure was even. The measurement of the three-dimensional atmospheric electric field provides a new means of observation for the study of atmospheric electricity.

Magnetic and electric field variations during geomagnetically active days over Turkey

Currents in the magnetosphere flow into the ionosphere during geomagnetic disturbances and are detected at the ground magnetic stations as Geomagnetically Induced Currents (GICs). In this paper, magnetic and electric field characteristics of the GICs at midlatitudes were studied using electric field and magnetic field observations in Turkey during the geomagnetically active intervals. A magnetotelluric station consisting of an electrometer and a magnetometer were set up in Bozcaada, Çanakkale (37.5°N, 106°E). Several cases that showed large electric and magnetic field fluctuations during geomagnetic disturbances were selected and the effects of geomagnetic activity were studied using the time derivatives of horizontal component of the magnetic field and the deviations in the magnetic and electric field components from the quiet background. In magnetic field data, quiet day Sq variations were removed using cubic spline fits. Similarly, the magnitude of the deviations in the electric field were determined by subtracting the background electric field determined by using cubic spline. Corresponding to the strong geomagnetic activity identified using Kp and Dst indices, high frequency, strong fluctuations in the magnetic field, its derivatives, and electric field were observed. These fluctuations in horizontal magnetic and electric field were compared with those seen during a magnetically quiet day. The close association between the fluctuations of the time derivatives of the horizontal magnetic field and electric field components were demonstrated. Two types of variations in the electric and magnetic fields corresponding to the different phases of the geomagnetic activity were identified: those corresponding to the initial phase including the sudden commencement and those to the main phase of the geomagnetic storm. The fluctuations in both magnetic field and electric field corresponding to the sudden commencement and the initial phase indicate the effects of magnetopause currents driven by the large solar wind dynamic pressure as associated with the coronal mass ejection (CME) events. Each event shows increased levels of ground level magnetic and electric field fluctuations corresponding to the CME compression at the subsolar magnetopause. High frequency, large fluctuations continue subsequently during the main phase in the presence of the geomagnetic storms. The fluctuations during the main phase were found to be different than those corresponding to the sudden commencements. GIC occurrences in our latitudes were shown to be associated with the sudden commencement and main phase of the geomagnetic storm activity. The time rate of change in horizontal component of the magnetic field showed perturbations on the order of 0.5nT/s in our region. The sources of the GICs based on these observations were discussed. This study presents our preliminary results on the characteristics of the GICs over Turkey based on the simultaneous measurements of electric and magnetic field during the geomagnetic storms. It is the first study of the GICs in Eurasia region and the results contribute to the worldwide understanding and modelling efforts on the GICs.

Enhanced plasmon coupling of partly embedded gold nanospheres with surrounding silicon

Gold nanospheres (AuNSs) were partly embedded into silicon through metal-assisted chemical etching, producing multiple-dimensional coupling of the plasmon resonances with the induced image charges in the surrounding medium. Rich plasmonic features of such coupling system were revealed by single particle dark-field scattering spectra, characterizing by two splitted multipolar resonances at short wavelength region and a mixed dipolar resonance extending to infrared region. Numerical electrodynamic calculations indicated that the multipolar modes arise from the in-plane and out-of-plane quadrupolar resonances, which are excited by the horizontal and verticle electric field components, respectively, of the incident light owing to the enhanced coupling interaction. As the embedding depth increases, the degree of symmetry breaking in such nanoparticles/substrate system changes, resulting in significantly modified optical response, which supplies a new way to modulate the optical properties of plasmonic nanoparticles.

Performance analysis of InGaAs/GaAsP heterojunction double gate tunnel field effect transistor

In this paper, analog/RF performance of InGaAs/GaAsP heterojunction double gate tunnel field effect transistor (HJTFET) has been explored. A highly doped n+ layer is placed at the Source-Channel junction in order to improve the horizontal electric field component and thus, improve the realiability of the device. The analog performance of the device is analysed by extracting current-voltage characteristics, transcondutance (gm), gate-to-drain capacitance (Cgd) and gate-to-source capacitance (Cgs). Further, RF performance of the device is evaluated by obtaining cut-off frequency (fT) and Gain Bandwidth (GBW) product. ION/IOFF ratio equal to ≈ 109, subthreshold slope of 27 mV/dec, maximum fT of 2.1 THz and maximum GBW of 484 GHz were achieved. Also, the impact of temperature variation on the linearity performance of the device has been investigated. Furthermore, the circuit level performance of the device is performed by implementing a Common Source (CS) amplifier; maximum gain of 31.11 dB and 3-dB cut-off frequency equal to 91.2 GHz were achieved for load resistance (RL) = 17.5 KΩ.

Transient surface impedance (TranSIM) measurements using discrete lightning for electromagnetic mapping at audio frequencies

The paper describes the first field measurements using recently developed TranSIM instrumentation. The method is based on registering horizontal components of electric and magnetic field of distant lightning strokes (sferics). In fact it is an expansion of classical MT method in the VLF frequency range of 3 to 30 kHz thus providing information about conductivity distribution at the depths of approximately 50 to 300 meters. Measurements are conducted atop basalt body in the vicinity of Ipswich (Queensland) over 16 sites on 2 parallel profiles. From 20 to 50 sferics were registered at every site. Data was processed using short time Fourier transform obtaining spectrograms of electric and magnetic field. Apparent resistivity was calculated and frequency pseudo sections are presented. The apparent resistivity sections were matched with geological scheme of the site. Highly resistive zones correlate with high thickness of a basalt layer and conductive zones show where the underlying basalt sandstone is closest to the surface.