Electric Field Components Research Articles

EMC Impact of Disturbances Generated by Multiple Sources

In this paper, the impact of an increasing number of arbitrary electrical/electronic devices on the overall radiated emissions is investigated. Understanding and quantifying such an impact are prerequisites to the proper evaluation of electromagnetic compatibility (EMC) of various electronic systems and devices and, if needed, to revisiting the international standards. To evaluate the radiated emissions from multiple electronic devices, each arbitrary electronic device is characterized using an equivalent Huygens’s surface, in which the tangential components of electric and magnetic near fields are calculated (or measured). The radiated emission from the arbitrary electronic device can be calculated using the electric and magnetic near fields for an arbitrary phase (correlated or uncorrelated), position, and orientation. The influence of several parameters affecting the radiated emissions from multiple arbitrary electronic devices, including the number of disturbance sources, the polarization of each device, the radiation pattern of each device, the location and orientation of each device, and the phase shifts between devices, are analyzed. The numerical results show that the mentioned parameters have a significant effect on the radiated emissions, and cannot be neglected in EMC considerations. In general, increasing the number of electronic devices leads to an increase in the level of radiated emissions. However, the increase depends on other parameters such as the arrangement (the radiation pattern for each device, the distance between the devices, and the orientation and/or polarization of each device). The proposed method can be straightforwardly applied to devices characterized by near-field measurements or multimodular large equipment with long cables.

Global Modeling of the Inner Magnetosphere Under the Influence of a Magnetic Cloud Associated With an Interplanetary Coronal Mass Ejection: Energy Conversion and Ultra‐Low Frequency Wave Activity

AbstractThe interaction and response of the magnetic cloud‐type structure with Earth's magnetosphere were modeled by the SWMF/BATS‐R‐US code. The conversion of magnetic (Em), kinetic (Ek), and internal (Ei) energies was analyzed as well as the wave power integrated in the ultra‐low frequency (ULF) range of the poloidal (Eϕ) and toroidal (Er) electric field components in the equatorial region of the magnetosphere, in seven 2‐hr long intervals, namely, I1 through I7. The intensity of energy conversion and wave activity for I1 and I7 intervals was negligible. The energy conversion started in the I2 interval and extended to the I3, I4, and I5 intervals. The power of the Eϕ and Er components in the dayside and nightside regions is clearly observed. The I4 corresponds to interplanetary magnetic field (IMF) Bz mostly southward and the I5 has similar amplitudes of the Bz and By components, corresponding to the period of the high geomagnetic activity. The conversion rate for the I4 and I5 was similar, however, the integrated power spectral density (IPSD) of the Eϕ and Er components is more intense in I5. During the I6 interval, with predominant IMF By, the energy conversion rate is intensified mostly for inner radial distances R < 6 RE, and the Ek component becomes close to zero for outer regions. The energy conversion regions are located spatially close to or overlapping with regions where the IPSD in the ULF range is intensified. The energy conversion in the inner magnetosphere occurred preferentially between Em and Ei, with the Ek energy component always present but with lower intensities.

Newly Formed Dawnside, Duskside, and Nightside Subauroral Flows Developed During Magnetically Active Times

AbstractWe study the newly formed (with an upper limit of ∼101 min) subauroral flows in the topside ionosphere. These include the dawnside subauroral flows observed at ∼5–6 magnetic local time (MLT), the duskside sub‐auroral polarization streams (SAPS) at ∼15 MLT, and the nightside sub‐auroral ion drifts (SAID) at ∼19–20 MLT. We employ the same types of observations for investigating the various underlying magnetospheric processes related to the development of the newly formed subauroral flows. These processes include (a) the stretching of magnetic field lines (leading to plasma density dropouts) due to the unfolding magnetotail reconnection, (b) the dawnside and nightside diversions of the magnetotail‐reconnection—related earthward plasma flows, (c) the ongoing particle injections, and (d) the trapping of ring current protons at subauroral and auroral latitudes. Based on these processes (a–d), we found strong similarities in the development of the newly formed dawnside and duskside/nightside subauroral flows investigated. At the dawnside plasmapause in the inner magnetosphere equatorial plane, the outward and duskward electric (E) field components provide observational evidence that the newly formed dawnside rapid narrow subauroral flows were SAID developing in the dawn sector. Evidence shows that the newly formed dawnside broad subauroral flow channel was associated with upward Region 2 (R2) field‐aligned currents (FACs) and equatorward subauroral polarization E field, and thus, was the dawnside equivalent of the duskside SAPS associated with downward R2 FACs and poleward subauroral polarization E field. Further evidence includes the inner magnetosphere observations of the hot zone both on the dusk/nightside and on the dawnside.

Surface excitation of focused shear wave beams in soft elastic media: Theory

Shear wave propagation is employed in medical ultrasound imaging, because it reveals variation in the viscoelastic properties of tissue. Frequencies below 1 kHz are required for imaging with shear waves in soft tissue due to their high attenuation and low propagation speeds, compared to compressional waves with frequencies above 1 MHz used for ultrasound imaging. Shear waves exhibiting particle motion in the direction of propagation, referred to as longitudinally polarized shear waves, can be generated by applying longitudinal motion of a circular disk to the surface of a soft elastic medium. This approach is used in practice because it permits imaging of the longitudinal shear wave with a conventional ultrasound transducer that is coaxial with the source of the shear wave. Presented here are the theoretical framework and numerical simulations that illustrate effects of focusing on longitudinally polarized shear waves. Longitudinal, transverse, radial, and torsional source polarizations are considered. The present investigation was motivated initially by an experimental study in optics due to Dorn et al. [Phys. Rev. Lett. 91, 233901 (2003)]. Our predictions for shear wave beams support their measurements of light beams revealing that the longitudinal electric field component produces a smaller focal spot than the transverse field component.

Numerical analysis of the spatial structure of Alfvén waves in a finite pressure plasma in a dipole magnetosphere

We have carried out a numerical analysis of the spatial structure of Alfvén waves in a finite pressure inhomogeneous plasma in a dipole model of the magnetosphere. We have considered three magnetosphere models differing in maximum plasma pressure and pressure gradient. The problem of wave eigenfrequencies was addressed. We have established that the poloidal frequency can be either greater or less than the toroidal frequency, depending on plasma pressure and its gradient. The problem of radial wave vector component eigenvalues was considered. We have found points of Alfvén wave reflection in various magnetosphere models. The wave propagation region in the cold plasma model is shown to be significantly narrower than that in models with finite plasma pressure. We have investigated the structure of the main Alfvén wave harmonic when its polarization changes in three magnetosphere models. A numerical study into the effect of plasma pressure on the structure of behavior of all Alfvén wave electric and magnetic field components has been carried out. We have established that for certain parameters of the magnetosphere model the magnetic field can have three nodes, whereas in the cold plasma model there is only one. Moreover, the longitudinal magnetic field component changes sign twice along the magnetic field line.

Численный анализ пространственной структуры альфвеновских волн в плазме конечного давления в дипольной магнитосфере

We have carried out a numerical analysis of the spatial structure of Alfvén waves in a finite pressure inhomogeneous plasma in a dipole model of the magnetosphere. We have considered three magnetosphere models differing in maximum plasma pressure and pressure gradient. The problem of wave eigenfrequencies was addressed. We have established that the poloidal frequency can be either greater or less than the toroidal frequency, depending on plasma pressure and its gradient. The problem of radial wave vector component eigenvalues was considered. We have found points of Alfvén wave reflection in various magnetosphere models. The wave propagation region in the cold plasma model is shown to be significantly narrower than that in models with finite plasma pressure. We have investigated the structure of the main Alfvén wave harmonic when its polarization changes in three magnetosphere models. A numerical study into the effect of plasma pressure on the structure of behavior of all Alfvén wave electric and magnetic field components has been carried out. We have established that for certain parameters of the magnetosphere model the magnetic field can have three nodes, whereas in the cold plasma model there is only one. Moreover, the longitudinal magnetic field component changes sign twice along the magnetic field line.

Fundamental Studies on Electron Dynamics in Exact Paraxial Beams with Angular Momentum

Classical electromagnetic radiation with orbital angular momentum (OAM), described by nonvanishing vector and scalar potentials (namely, Lorentz gauge) and under Lorentz condition, is considered. They are employed to describe paraxial laser beams, thereby including non-vanishing longitudinal components of electric and magnetic fields. The relevance of the latter on electron dynamics is investigated in the reported numerical experiments. The lowest corrections to the paraxial approximation appear to have a negligeable influence in the regimes treated here. Incoherent Thomson scattering (TS) from a sample of free electrons moving subject to the paraxial fields is studied and investigated as a beam diagnosis tool. Numerical computations elucidate the nature and conditions for the so called trapped solutions (electron motions bounded in the transverse plane of the laser and drifting along the propagation direction) in long quasi-steady laser beams. The influence of laser parameters, in particular, the laser beam size and the non-vanishing longitudinal field components, essential for the paraxial approximation to hold, are studied. When the initial conditions of the electrons are sufficiently close to the origin, a simplified model Hamiltonian to the full relativistic one is introduced. It yields results comparing quite well quantitatively with the observed amplitudes, phase relationships and frequencies of oscillation of trapped solutions (at least for wide laser beam sizes). Genuine pulsed paraxial fields with OAM and their features, modeling true ultra-short pulses are also studied for two cases, one of wide laser beam spot (100 μm) and other with narrow beam size of 6.4 μm. To this regard, the asymptotic distribution of the kinetic energy of the electrons as a function of their initial position over the transverse section is analyzed. The relative importance of the transverse structure effects and the role of longitudinal fields is addressed. By including the full paraxial fields, the asymptotic distribution of kinetic energy of an electron population distributed across the laser beam section, has a nontrivial and unexpected rotational symmetry along the optical propagation axis.

Structured Vector Field Manipulation of Terahertz Wave along the Propagation Direction Based on Dielectric Metasurfaces

AbstractThe generation and manipulation of vector light fields are of great significance for both fundamental research and industrial applications of polarized optics. In recent years, the spatial domain control of structured vector fields has gradually expanded from two‐ to three‐dimensional, including traditional optics and meta‐optics. Here, a new method to generate and manipulate structured vector light fields along the propagation direction is proposed, and the functionality in terahertz band using all‐silicon metasurfaces is demonstrated. The coherent superposition of orthogonal circularly polarized terahertz waves through long focal depth and multifocal metalens is completed, and varying phase differences between them in the propagation direction via path accumulation or initial phase design are introduced, thereby continuous variation or independently designed vector polarization distributions in multiple planes are obtained. It is worth mentioning that the proposed scheme is not only for the design of transverse electric field components, but also shows a strong ability for manipulation of the longitudinal component. This scheme realizes the polarization distribution designs of three‐dimensional vector fields in three‐dimensional space, and provides a new inspiration for the generation and manipulation of vector beams based on meta‐optics.

Concise and explicit expressions for typical spatial-structured light beams beyond the paraxial approximation.

Structured light beams with distinct spatial inhomogeneity of amplitude, phase, and polarization have garnered tremendous attention in recent years. A better understanding of the vectorial structure of such beams is helpful to reveal their important and interesting features for further applications. In this paper, explicit analytical expressions for the electric field components of typical spatial-structured light beams, including fundamental Gaussian beams, Hermite-Gaussian beams, Laguerre-Gaussian beams, Bessel/Bessel-Gaussian beams, and Airy beams, beyond the paraxial approximation are derived on the basis of the vectorial Rayleigh-Sommerfeld diffraction integrals. Compared with the existing expressions in the literature, the expressions given in this paper are very concise. Using the derived analytical expressions, distributions of the electric field components of these typical structured light beams are displayed and analyzed.

Surface-standing-wave formation via resonance interaction of a finite-length conductive rod with microwaves

The resonant response of a thin conducting rod with a finite length irradiated by microwaves polarized along its axis is observed. By using a thermoelastic optical indicator microscope it is shown that rod with a length of several half- wavelengths can serve as a resonator for axial surface waves. It is facilitated by noticeable reflections (approximately 30%) from the rod edges conditioned by the unique distributions of Sommerfeld wave fields along a rod. The presence of a weak axial electric field component of surface waves ensures an easy coupling with the incident plane wave polarized along the rod axis and excites the resonator. Visualization of distributions of the near-field magnetic component of surface standing waves in the vicinity of a rod allows the exploration of three longitudinal modes of a resonator with low orders. The possibility of controlling the resonant frequency by changing the length and diameter of the rod, as well as the electromagnetic characteristics of the environment, are studied. The phenomenon under study can be used to create wavefront shaping metasurfaces and for studies of the properties of a dielectric medium in the microwave region. As Sommerfeld waves propagate on the surface of a cylindrical resonator, the resonant properties are sensitive to the dielectric permittivity of the surrounding medium, which will open up the potential for using the suggested resonator in sensing applications, which is experimentally demonstrated.

Characterisation of surface charge density and net electric field during parallel-plate dielectric barrier discharge generated in atmospheric-pressure air

We measured the surface charge density in a parallel-plate dielectric barrier discharge (DBD) using the Pockels effect, and the axial and lateral components of the net electric field were evaluated for different gap lengths and applied voltages. The DBD was driven by a 5 kHz sinusoidal voltage in gap lengths of 0.5, 0.3, and 0.1 mm at atmospheric pressure with Bi4Ge3O12 crystal as a dielectric. Typical microdischarges (MDs) were observed for every gap length, and the number of MDs increased with the increasing applied voltage. As the gap length decreased, the spot radius of a single MD decreased, whereas the peaks of charge density were almost the same, indicating that the amount of charge transported per unit MD is limited for short gaps. The spatial memory effect, in which MDs occur at the same position in successive cycles, was not always observed under the experimental conditions, and it was evaluated considering the surface charge density distributions. Whether the memory effect works is determined by the surface charge density, and it is likely to occur under a balance between positive and negative charges across successive half-cycles. The net electric field was estimated from surface charge measurements. The axial component of the net electric field strength increased up to 150–170 Td before the MD occurred, and it decreased below 100 Td by the surface charge deposited by MD, being approximately 50%–60% of the external field amplitude. The maximum value of the lateral component of the electric field was approximately 150 Td at the edge of the MD spot with a gap length of 0.5 mm, and it decreased as the gap length decreased. As a negative surface charge generated a weaker lateral field than a positive one, the electric field distribution differed between anodic and cathodic dielectrics.

Statistical Analysis of Pi2 Pulsations Observed by Van Allen Probes

AbstractThe relative importance of propagating and cavity mode waves remains an important question regarding the generation of Pi2 pulsations detected on the ground. To determine the wave mode, we statistically generate spatial maps of magnetospheric oscillations that are coherent with ground Pi2 pulsations. The magnetospheric observations were made by the two Van Allen Probes spacecraft over a 7‐year period. The amount and quality of the spacecraft data allow us to investigate the mode structure of Pi2 pulsation in ways that were not possible in previous studies. We use the H component of low‐latitude ground Pi2 pulsations detected in the 22–02 magnetic local time (MLT) sector as the reference signal to generate L‐MLT and meridional maps of the coherence, amplitude, and phase of the magnetospheric electric and magnetic field components defined in magnetic field aligned coordinates. We identify low‐frequency and high‐frequency components in Pi2 power spectra, and we are able to determine the mode structure of the high‐frequency events for the first time. The maps demonstrate that the poloidal components have higher coherence than the toroidal components. For each frequency component, the maps of the poloidal components agree with those of cavity mode oscillations obtained in a numerical simulation using realistic models for the magnetospheric mass density and magnetic field. This result is conclusive evidence of the cavity mode nature of Pi2 pulsations detected in the inner magnetosphere.

Results of the Study of Variations in the Surface Electric Field and Secondary Components of Cosmic Rays in a Seismic Active Zone

Results of the Study of Variations in the Surface Electric Field and Secondary Components of Cosmic Rays in a Seismic Active Zone

Investigation of electromagnetic plasma waves in the process of formation and growth of plasmoid instability in solar corona in two regimes ωce>< ωpe

Using two-dimensional particle-in-cell simulation of collisionless plasmoid instability, the waves generated during formation and growth of plasmoids are investigated. Magnetic reconnection is recognized as a fundamental phenomenon in the conversion of magnetic energy into heating energy and particles acceleration in space and astrophysical plasmas. In this phenomenon stored magnetic energy abruptly released in form of violent plasma jets and non-thermal particles acceleration and relativistic particle acceleration. In large systems such as solar systems that the length of the current layer is much greater than its thickness ,current sheets are affected by complex photospheric motion or external disturbances such as the eruption motion of magnetic structures. This violent plasma instability results in the breakup, fragmentation and formation of multiple current sheets. Therefore reconnection happens at several X points and magnetic islands or plasmids appear. Plasmoid chains are highly dynamic configurations and can fastly grow by coalescence bounce and repel smaller plasmoids. Understanding of the effects of charged particles on the earth's atmosphere depends on a better understanding of the plasmoid instability that we have addressed an aspect of it in this article. The acceleration of charged particles toward the earth's atmosphere is one of the most important consequences of magnetic reconnection and the formation of plasmids in the solar corona as well as in magnetopause and in the magnetotail. The study of electric field components, which are the most important factor of particle acceleration, is very important in recognizing these charged particles. Fourier analysis of electric field components shows different types of electromagnetic and electrostatic waves during the formation and growth of plasmoid instability in both states ωce> ωpe and ωce< ωpe. This analysis reveals that two electromagnetic right and left-hand polarized modes and whistler wave parallel to the initial magnetic field and also the extraordinary mode, ordinary mode and magnetosonic wave perpendicular to the current sheet are excited.

Quasibound states in a one-dimensional grating for electro-optic modulation

For modulation in free space using the linear electro-optic effect, a narrow-linewidth resonance is favorable when a minimal voltage is preferred to fully shift the resonance. Here a method is proposed to engineer the quasibound states in a slab waveguide consisting of electro-optic polymer and metal gratings, in order to achieve narrow-linewidth resonances for electro-optic modulation. This quasibound state features a strong out-of-plane electric field component located at the position of the metal strips constituting the grating, which also work as the interdigitated electrodes, and thus, the optical mode can interact with the electrostatic field efficiently. The radiation damping of the quasibound state can be controlled by changing the relative position of the neighboring metal strips, while the optical mode can maintain the same periodicity as the electrostatic field. This method also offers prospects for engineering narrow-linewidth resonances for other applications.

Implementation of typical structured light beams in discrete dipole approximation for scattering problems

In this work, we report an implementation of typical structured light beams, including the Hermite-Gaussian beams, Laguerre-Gaussian beams, Bessel beams, and Airy beams, in the discrete dipole approximation (DDA) for scattering problems of small particles. The analytical expressions for the electric field components of these beams are presented, and the detailed processes for the implementation of these beams in DDA are given, with particular emphasis on the explicit codes. The calculated result for our codes of Gaussian beams is compared with that from the Amsterdam DDA codes, and very good agreement is observed. The internal and near-surface fields of a sphere illuminated by the typical structured light beams with different beam parameters are illustrated and discussed. Also, the intensity distributions of internal and near-surface fields as well as the scattering efficiency factor for the scattering of structured light beams as mentioned above by sphere, spheroid, and cylinder are presented. The proposed codes can be directly used for the investigation of scattering of typical structured light beams by complex particles within the framework of the DDA.

Exploring a Directional Measurement Method of Three-Dimensional Electric Field Intensity in the Atmosphere

The traditional process of measuring a three-dimensional (3D) electric field in the atmosphere may suffer from limited accuracy of the electric field component intensity due to multiple factors, such as the 3D electric field sensor’s pose change due to the sensor-carrier motion and the non-parallel positions between the 3D electric compass and field sensor’s measurement axes. Thus, this paper proposes a modified 3D electric field directional decomposition algorithm to overcome this problem. Specifically, the developed solution utilizes a parameter identification and fine-tuning scheme that solves the inaccurate measurement problem caused by the non-coaxial 3D positions between the electric field sensor and the compass. The measurement results highlight that the proposed method eliminates the instability of the electric field intensity measurement errors caused by the 3D electric field sensor changes because the measurement accuracy of the corrected electric field component intensity does not change with the sensor’s rotation angle. Our technique reduces the measurement error of the electric field intensity originating from the non-parallel position 3D electronic compass and field sensor measurement axes, further improving the measurement accuracy of the atmospheric field intensity.

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%.

Transmission-type reconfigurable metasurface for linear-to-circular and linear-to-linear polarization conversions

We present a transmission-type polarization conversion metamaterial (PCM) whose functions can be dynamically switched among the linear-to-circular (LTC) and linear-to-linear (LTL) polarization conversions. The proposed PCM consists of a grating, a polarization conversion surface and a reconfigurable polarization selective surface incorporated with PIN diodes. By changing the states of diodes, the PCM can achieve the reconfigurable manipulations for incident waves. The Fabry–Pérot (F–P) resonances excited by the PCM contribute to the polarization conversions, as is illustrated. Moreover, through establishing the F–P-like cavity model and analyzing the electric field components of the transmitted waves, the conditions for realizing LTC polarization conversion are revealed, which can guide the construction of PCM. The prototype of PCM is fabricated and measured, which can achieve LTC and LTL polarization conversions within 3.31–3.56 GHz and 2.76–4.24 GHz, respectively, the polarization conversion ratios of two functions are higher than 0.95. The measurement results are in agreement with the simulation data.

An Electrohydrodynamic analysis for the characterisation of fluid flow within conducting and non-conducting channels

This paper presents a generalized non-dimensional theoretical formulation with boundary conditions to analyze the EHD flow within the conducting and non-conducting channels. The substantial effect of normal and tangential components of electric field on fluid flow within the channel is presented through simulation results based on the non-dimensional parameters of strength, penetration, and repulsion of electric forces. The simulation results reveal that the normal component of induced electric field transits the flow regime within surfaces of a channel. The tangential component of applied electric field increases the thickness of viscous boundary layer, leading to skewed velocity profiles.