Emission Of Electromagnetic Waves Research Articles

Novel particle-based model of negative corona in oxygen for investigation on emission of electromagnetic waves

In recent years, the ultrahigh frequency (UHF) partial discharge (PD) measurement technique has gained more attention as an effective approach towards condition monitoring of power transformers. In this contribution, a novel model for the simulation of negative corona, based on particles' movement, is presented and implemented in COMSOL Multiphysics. Unlike existing models of PD, this model aims at an accurate representation of the phenomenon from an electromagnetic (EM) viewpoint. Following a discussion on the theoretical fundamentals of PD, the model containing the mechanisms and processes that occur during the PD phenomenon and lead to propagation of EM waves is discussed. Subsequently, simulation results are analyzed and previously ambiguous properties of negative corona are interpreted and some efforts are done to validate the theory using experimental measurement.

A first proof of principle booster setup for the MADMAX dielectric haloscope

Axions and axion-like particles are excellent low-mass dark matter candidates. The MADMAX experiment aims to directly detect galactic axions with masses between 40 and 400,upmu mathrm{eV} by using the axion-induced emission of electromagnetic waves from boundaries between materials of different dielectric constants under a strong magnetic field. Combining many such surfaces, this emission can be significantly enhanced (boosted) using constructive interference and resonances. We present a first proof of principle realization of such a booster system consisting of a copper mirror and up to five sapphire disks. The electromagnetic response of the system is investigated by reflectivity measurements. The mechanical accuracy, calibration process of unwanted reflections and the repeatability of a basic tuning algorithm to place the disks are investigated. We find that for the presented cases the electromagnetic response in terms of the group delay predicted by one-dimensional calculations is sufficiently realized in our setup. The repeatability of the tuning is at the percent level, and would have small impact on the sensitivity of such a booster.

Scattering and Emission of Electromagnetic Waves From Random Layered Media With Random Rough Interfaces: A Partially Coherent Cascading Approach

A partially coherent approach for computing the electromagnetic response of a layered medium having random rough interfaces and a random dielectric profile is presented as an alternative to the full-wave solution of the problem. The statistical nature of this problem, in particular, the random dielectric profile, introduces randomness in the phase of the electromagnetic field such that the field loses its phase coherency after traveling in the layered medium for a few correlation lengths of the permittivity. In this situation, there is a coherency length within which a coherent solution of Maxwell’s equation is required. For the distances beyond this coherency length, a combined coherent–incoherent cascading approach can be applied to reduce the computational complexity of the problem. The coherent response of each “block” within the medium (with a length approximately the coherency length) can be cascaded incoherently ignoring the phase response without losing accuracy. Cascading equations for block bistatic scattering are applied, and solutions of the equivalent block parameters are obtained by iteration up to the second order of multiple scattering. The proposed method is described in this article, and the numerical results are shown to compare the proposed cascading approach with the results obtained from the fully coherent solution.

Evidence for Magnetar Precession in X-Ray Afterglows of Gamma-Ray Bursts

Abstract Many gamma-ray bursts are followed by periods of extended emission. At least in some cases, the burst afterglow may be powered by a rapidly rotating, highly magnetized neutron star, which spins down due to electromagnetic and gravitational-wave emission. Such a remnant is likely to strongly precess in the early stages of its life, which would lead to modulations in the X-ray luminosity as the triaxiality of the system evolves over time. Using a radiation profile appropriate for a precessing, oblique rotator, we find that Swift-XRT data of a long (080602) and a short (090510) burst matches the model with significantly higher accuracy (mean-square residuals dropping by ≳200% in the early stages of the extended emission) than for an orthogonal rotator. We interpret this as evidence for precession in newborn magnetars.

A Study on Transverse Magnetic Wave Propagation Characteristics of Dielectric Wrapped Wire

The transverse magnetic wave propagation characteristics of the dielectric wrapped wires are studied. The transverse magnetic wave transmission model of a dielectric wrapped wire is revised based on the variable seperation method. The spatial relationship between electromagnetic wave emission and reflection is obtained. An experiment is developed using the new actuator and coupler. The results show that the surface wave guide formed by a single wire wrapped in a low loss medium can ben used as a high speed data transmission channel.

Microwave source with enhanced radiation power based on orbitron MASERs

We have proposed the design of high power microwave source in a vacuum tube based on the theory of negative mass instability. The proposed source does not operate based on a slow-wave structure but instead makes use of accelerated charged particles. In our structure, an electron emitter injects the charged particles into to the cavity. Emitted particles move around the anode, which leads to electron acceleration and emission of electromagnetic waves with a specific frequency. In this paper, we have enhanced the output power and frequency of microwave source by variation of particles initial energy and the number of anodes incorporating their specific arrangement and applied voltages. Working at room temperature, compactness, wide bandwidth, and tunability of output frequency are among the advantages of the proposed source.

Estimation of the Power of the Anomalous Microwave Emission

Context and Background: The product of the electromagnetic (EM) wave’s power P times its period τ, i.e. Pτ, is the amount of energy conserved in EM wave’s absorption in matter. Whether Pτ is the amount of energy conserved in the emission of EM waves from matter is not assessed. Motivation: In this research, we perform a computational study to explore the ability of Pτ to represent the amount of energy conserved in EM wave’s emission from matter. Hypothesis: Since the magnitude of the power P of emitted EM waves computed through Larmor’s formula for a rotating dipole is excessively small, we alternatively hypothesize that Pτ and the law of conservation of energy can lead to a realistic estimation of P. Methods: We estimate the power PAME of the anomalous microwave emission (AME), a well-characterized radiation generated in the interstellar medium (ISM) by spinning dust grains, and one possible source of contamination of the cosmic microwave background (CMB). For our estimation of PAME, we assume the AME to be generated in a molecular cloud mostly populated by spinning silicate nanoparticles (SSNs) or polycyclic aromatic hydrocarbon (PAH) spinning dust grains. Indeed, SSNs and PAHs are listed among the most probable sources of AME, and their characteristics are well-known. We discriminate between realistic and non-realistic values of PAME based upon the magnitude of two parameters that depend on PAME: the significant distance z, and the time of photon production T. The parameter z is the space interval from the spinning dust grain within which the spinning dust grain’s electric field is effective. Results: Using the information available for AME, SSNs and PAHs, we estimate the power PAME using both Larmor’s formula and Pτ. We compare and comment the results obtained for z and T. Conclusions: Our study highlights the effectiveness of Pτ over Larmor’s formula in providing a realistic value of PAME. This finding might have consequences in quantum technology of single photon detection and production.

Radiation in the Optical and UHF Range Emitted by Partial Discharges

This paper presents the results of analysis of a solid dielectric’s influence on the phenomena associated with the signals emitted by surface partial discharges. Three types of electrode systems were tested, in which solid dielectrics made of pressboard, Teflon, and glass were used. The emission of such signals as radio waves in the Ultra high frequency (UHF) range and optical radiation was analyzed. The measurements were carried out in the insulation systems most commonly used in electrical power equipment, i.e., mineral oil and air. UHF and optical spectrophotometry methods were used to register the emitted signals. The obtained results indicate that the type of material from which the dielectric solid is made may have a potential impact on some ranges of emitted electromagnetic waves during the surface electrical discharges. The research topic undertaken is important in issues associated with high-voltage insulation systems and in particular with surface discharges, which are often the cause of their damage.

Precursor Wave Amplification by Ion–Electron Coupling through Wakefield in Relativistic Shocks

Abstract We investigated electromagnetic precursor wave emission in relativistic shocks by using two-dimensional particle-in-cell simulations. We found that the wave amplitude is significantly enhanced by a positive feedback process associated with ion–electron coupling through the wakefields for high magnetization. The wakefields collapse during the nonlinear process of the parametric decay instability in the near-upstream region, where nonthermal electrons and ions are generated. The intense coherent emission and the particle acceleration may operate in high-energy astrophysical objects.

Emission of electromagnetic waves from walls of esophagus under domination of wall slip effect

Abstract On explanation of biomedical applications and its complexity, the contraction and relaxation of Eyring-Powell fluid in esophagus has turned out to be notable amongst the challenging research fields of fluid mechanics. Therefore, the main idea of this paper is to classify the simultaneous significances of compliant walls and emission of electromagnetic waves from walls of electrically conducting Eyring-Powell fluid. Conductivity of the fluid is increased by adding the Brownian motion and thermophoresis effects. Moreover, the velocity of the channel and the fluid particles near the surfaces are assumed to be different. Due to vertical contraction and relaxation, the body forces are taken in the form of mixed convection. The dimensionless variables are utilized to convert the required partial differential equations including mass, momentum and energy into dimensionless form. The solutions of the reduced partial differential equations subject to the given boundary conditions are calculated by using Mathematica. Moreover, the various solutions for dimensionless fluid concentration, velocity, and temperature distributions are captured for different values of embedded parameters. The different dimensionless parameters governing the flow, heat and mass transfer characteristics are the Schmidt number, radiation parameter, Hartmann number, local temperature Grashof number, slip parameters, local nanoparticles Grashof number, thermophoresis parameter, Brownian motion parameter, fluid parameters and Prandtl number. Maximum velocity is noted an increasing function of velocity slip parameter. Further maximum temperature enhances by increasing Brownian motion and thermophoresis parameters. More specifically the effects of slip parameters, Brownian motion and thermophoresis parameters on the flow stream have been examined. The velocity profile shows enhance behavior for large values of velocity parameter and mixed convection, whereas, reverse impact is noticed for magnetic field. Increasing concentration slip parameter causes reduction in nanoparticle volume fraction, while temperature of the fluid rises by increasing thermal slip parameter.

A Study on the Effects of Cellular Mobile Networks on People in Tikrit City Based on Power Density Measurements and Calculations

In this paper, the emitted electromagnetic waves (EMW) from different cellular mobile base stations (BSs) have been measured and calculated in order to study their effects on public health. Moreover, a comparison between the effect of radiated power from the BSs on people who live near them and those who live away has been made by using OpenSignal software and calculated theoretically. The values of power density for different cells were also calculated to compare them with the maximum permissible exposure limit-the acceptable range values of power density. The measurements were done in Tikrit City considering ten cells and various locations and distances. The results show that most of the power density and EMV for the tested cells are within the acceptable range. However, power density and EMV for two of tested cells have hurtful effects in the long term for people who live near the BSs.

Telecommunications on Earth and their possible relation with the anthropic principle

The society of the information is based on the ability of humans to communicate in real time. This is possible thanks to the emission of electromagnetic waves. In this work it is discussed, by analyzing the round trip time (RTT) parameter, if it is possible to expand the society of the information out of the Earth. The results show that the value of the speed of light limits this expansion. Real time applications, such as videogaming, remote surgery, or voice conversations, are only possible on Earth and its proximities, which indicates that there could be a relation between real time telecommunications on Earth and the anthropic principle.

Estimation of radio emission from neutrino induced showers in rock salt above 1018 eV

Emission of electromagnetic waves from high energy particle showers is a powerful tool that can be used to detect the most elusive cosmic neutrinos of astrophysical or cosmogenic origin. We present here simulations of showers with a primary energy in the range 1018−1021 eV initiated by νe, νμ and ντ neutrinos. A medium that is both dense and transparent in the low radio frequencies part of the electromagnetic spectrum, like rock salt, is used as active medium where the shower develops. The calculation of the radio signal was performed by approximating the shower with a current density using the longitudinal profile of the charge excess, for estimation at low frequencies, below 500 MHz.The aim of this work is to give estimates of the amplitude of the signal induced by νe, νμ and ντ neutrinos.

Supermassive Binaries in Quasars and BL Lac Objects: Electromagnetic and Gravitational Wave Emissions

Abstract The search in active galactic nuclei (AGNs) for supermassive binary systems with total mass M ∼ 108–109 M ⊙ is intertwined with the observational efforts aimed at their contributions to the stochastic background of gravitational waves (GWs). Here we discuss and compare two classes of AGNs that are outstanding in electromagnetic bands: bright, relatively distant and massive quasars, and closer jetted and less massive BL Lac objects (BL Lacs). Among the latter, we focus on the source PG 1553+113 at redshift z ≃ 0.5, one of the best periodic candidates so far, that features a five-fold repetitive pattern of period P = 2.2 yr recurring in its gamma-ray light curve, as continuously monitored by Fermi-LAT for over 9 yr and updated here to 2018 March 15. We discuss this object as an interesting candidate for hosting a supermassive binary source of GWs, and explore the possible contributions to the GW stochastic background from it and similar sources in the BL Lac class. We find the possible contributions of such sources to lie below the limits set by the current Pulsar Timing Arrays, but well within the reach of the upcoming Square Kilometer Array.

Spectral dynamics of shift current in ferroelectric semiconductor SbSI

Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells.

Квадрупольное излучение незаряженной капли, осциллирующей в однородном электростатическом поле

AbstractCapillary oscillations of an uncharged spheroid droplet of nonviscous conducting uncompressible liquid in the presence of uniform electric field are analyzed in the first order of smallness with respect to the ratio of the oscillation amplitude to a linear size of the droplet and in the second order of smallness with respect to the squared ratio of the linear size to the radiation wavelength. It is shown that the electric quadrupole moment of the droplet is time-dependent due to surface oscillations, which lead to the emission of quadrupole electromagnetic waves. A mathematical model of the quadrupole electromagnetic radiation of an uncharged droplet that oscillates in the presence of electrostatic field is constructed, and the radiation intensity and frequency are estimated.

Innovations in polymer nanocomposite coatings for EMI Shielding applications

Start Excessive usage of electronic gadgets, telecommunication devices and electrical appliances has led to unwanted electromagnetic interference (EMI) as side effect. The EMI pollution interferes with the performance and functioning of the electrical equipments, which is generated through the conduction or radiation of emitted electromagnetic (EM) waves. In addition to affecting the quality of electrical appliances, EMI has a huge negative impact on the health and life of living organisms. Moreover, microwave frequency operated functions such as radar surveillance systems; weather radar, military aviation, radar guns, wireless technology and satellite communication are more prone to EMI pollution and specifically with regard to stealth purposes. In this paper carbon nanomaterial based polyurethane nanocomposites have been synthesized and investigated for decreasing the EM wave pollution due to their light weight, flexibility, optimum conductivity and good dielectric properties. Three different types of graphene sheets such as thermally reduced and exfoliated graphene (TRG); chemically reduced graphene (CRG) and Polyvinyl-pyyrolidone stabilized silver nanoparticles based graphene nanohybrid (Ag-PVP-CRG) have been synthesized and characterized for EMI shielding properties. Further, TRG, CRG and Ag-PVP- CRG sheets have been dispersed in thermoplastic polyurethane (TPU) polymeric matrix to create multifunctional nanocomposite films with properties such as EMI shielding, electrically conductivity and dielectric behavior. The study presents for the first time a comparative evaluation of three different types of graphene sheets in both neat and nanocomposite form. The synthesis of Ag-PVP-CRG nanohybrids and its application for EMI shielding is novel and reported for the first time for such an application.

Electromagnetic Wave Emissions from a Turbulent Plasma with Density Fluctuations

Abstract In the solar wind, Langmuir turbulence can generate electromagnetic waves at the fundamental plasma frequency ω p . This process can likely result from either linear wave transformations on the ambient random density inhomogeneities or resonant three-wave interactions involving Langmuir waves and ion acoustic oscillations. In the presence of sufficiently intense plasma density fluctuations of scales much larger than the Langmuir wavelengths, the first mechanism may be more efficient than the second one. A new approach to calculate the electromagnetic wave emissions by Langmuir wave turbulence in plasmas with background density fluctuations is developed. The evolution of the Langmuir turbulence is studied by numerically solving the Zakharov equations in such a two-dimensional plasma. The dynamics of the spatial distributions of the electric currents with frequencies close to ω p is calculated, as well as their emission into electromagnetic waves. The efficiency of this radiation is determined as a function of the level of the Langmuir turbulence, the characteristics of the density fluctuations, the background plasma temperature, the position of the satellite receiver, and the durations of the source’s emissions and spacecraft’s observations. The results obtained by the theoretical modeling and numerical simulations are successfully compared with space observations of electromagnetic waves radiated during Type III solar radio bursts.

Microwave emission from superconducting vortices in Mo/Si superlattices

Most of superconductors in a magnetic field are penetrated by a lattice of quantized flux vortices. In the presence of a transport current causing the vortices to cross sample edges, emission of electromagnetic waves is expected due to the continuity of tangential components of the fields at the surface. Yet, such a radiation has not been observed so far due to low radiated power levels and lacking coherence in the vortex motion. Here, we clearly evidence the emission of electromagnetic waves from vortices crossing the layers of a superconductor/insulator Mo/Si superlattice. The emission spectra consist of narrow harmonically related peaks which can be finely tuned in the GHz range by the dc bias current and, coarsely, by the in-plane magnetic field value. Our findings show that superconductor/insulator superlattices can act as dc-tunable microwave generators bridging the frequency gap between conventional radiofrequency oscillators and (sub-)terahertz generators relying upon the Josephson effect.

Broadband Terahertz Generation via the Interface Inverse Rashba-Edelstein Effect.

Novel mechanisms for electromagnetic wave emission in the terahertz frequency regime emerging at the nanometer scale have recently attracted intense attention for the purpose of searching next-generation broadband THz emitters. Here, we report broadband THz emission, utilizing the interface inverse Rashba-Edelstein effect. By engineering the symmetry of the Ag/Bi Rashba interface, we demonstrate a controllable THz radiation (∼0.1-5 THz) waveform emitted from metallic Fe/Ag/Bi heterostructures following photoexcitation. We further reveal that this type of THz radiation can be selectively superimposed on the emission discovered recently due to the inverse spin Hall effect, yielding a unique film thickness dependent emission pattern. Our results thus offer new opportunities for versatile broadband THz radiation using the interface quantum effects.