Transverse Electromagnetic Waves Research Articles

Influence of the Angular Distribution of Langmuir Waves on the Directivity of Radio Emission at Double Plasma Frequency

The directivity of transverse electromagnetic waves generated in a plasma at a double plasma frequency during the coalescence of plasma waves is calculated for various angular distributions of these waves. It is shown that the directivity of the generated electromagnetic waves is determined by the angular distribution of the spectral energy density of the Langmuir waves and is practically independent of the turbulence spectrum. The case of axial symmetry of emitting area is considered. If the angular distribution of Langmuir waves is proportional to cosδ ϑ, where ϑ is the angle between the direction of the wave vector of the Langmuir wave and the axis of the symmetry of the emitting region, the maximum of the generated transverse waves corresponds to viewing angles of α = 30°–45°, where the viewing angle is the angle between the line of sight and the axis of the emitting-area symmetry. In this case, the ratio of the maximum intensity of the generated radiation to the minimum can reach 3. If the angular distribution of turbulence is proportional to sinδ ϑ, then the radio-emission maximum corresponds to viewing angles of α = 60°–120°. This anisotropy of the solar plasma radiation can be measured with radio observations, which will make it possible to draw a conclusion about the nature and source of Langmuir turbulence in the solar plasma.

Enabling High‐Speed Computing with Electromagnetic Pulse Switching

AbstractCommunication and transfer of information from one block to another within a system is fundamental for high‐speed and efficient computing. Herein, a simple approach for computing, without using conventional electrical charge/discharge‐based primitive operations, in which information is represented in electromagnetic energy steps travelling in sections of transmission lines, is proposed. These steps are formed by transverse electromagnetic (TEM) square pulses with a polarity representing the values of Boolean variables. Logical operations between variables are realized at the crossing point of inter‐connected transmission lines by exploiting the known laws of reflection and transmission of TEM waves allowing power division and/or recombination. A series and parallel configurations for at‐will square pulse manipulation are discussed, offering new possibilities for future electromagnetic pulse‐based computing systems.

Realization of acoustic spin transport in metasurface waveguides

Spin angular momentum enables fundamental insights for topological matters, and practical implications for information devices. Exploiting the spin of carriers and waves is critical to achieving more controllable degrees of freedom and robust transport processes. Yet, due to the curl-free nature of longitudinal waves distinct from transverse electromagnetic waves, spin angular momenta of acoustic waves in solids and fluids have never been unveiled only until recently. Here, we demonstrate a metasurface waveguide for sound carrying non-zero acoustic spin with tight spin-momentum coupling, which can assist the suppression of backscattering when scatters fail to flip the acoustic spin. This is achieved by imposing a soft boundary of the π reflection phase, realized by comb-like metasurfaces. With the special-boundary-defined spin texture, the acoustic spin transports are experimentally manifested, such as the suppression of acoustic corner-scattering, the spin-selected acoustic router with spin-Hall-like effect, and the phase modulator with rotated acoustic spin.

Long‐Range Longitudinal Electric Wave in Vacuum Radiated by Electric Dipole: Part I

AbstractIn this work, by using the assumptions that wavelength is much smaller than charge separation distance of an electric dipole, which in turn is much smaller than a distance up to the point of observation, the new results for radiation of an electric dipole were obtained. These results generalize and extend the standard classical solution, and they indicate that under the above assumptions, the electric dipole emits both long‐range longitudinal electric and transverse electromagnetic waves. For a specific values of the dipole system parameters, the longitudinal and transverse electric fields are displayed. Total power emitted by electric and electromagnetic waves are calculated and compared. It was shown that under the standard assumption of charge separation distance being much smaller than wavelength, (a) classical solution correctly describes the transverse electromagnetic waves only; (b) longitudinal electric waves are nonnegligible; (c) total radiated power is proportional to the fourth degree of frequency and to the second degree of the charge separation distance; and (d) transverse component of our solution reduces to classical solution. In case wavelength is much smaller than charge separation distance, (a) the classical solution is not valid, and it overestimates the total radiated power; (b) longitudinal electric waves are dominant and transverse electromagnetic waves are negligible; (c) total radiated power is proportional to the third degree of frequency and to the charge separation distance; and (d) most of the power is emitted in a narrow beam along the dipole axis; thus, emission of waves is focused as with lasers.

4π-spherically focused electromagnetic wave: diffraction optics approach and high-power limits.

The focused field and its intensity distribution achieved by the 4π-spherical focusing scheme are investigated within the framework of diffraction optics. Generalized mathematical formulas describing the spatial distributions of the focused electric and magnetic fields are derived for the transverse magnetic and transverse electric mode electromagnetic waves with and without the orbital angular momentum attribute. The mathematical formula obtained shows no singularity in the field in the focal region and satisfies the finite field strength and electromagnetic energy conditions. The 4π-spherical focusing of the transverse magnetic mode electromagnetic wave provides the highest field strength at the focus and the peak intensity reaches 1026 W/cm2 for the laser power of 100 PW at 800 nm wavelength. As an example of using the mathematical formula, the electron-positron pair production via the Schwinger mechanism is analyzed and compared with previous results.

On the Calculation of the Spectral Bands of One-Dimensional Photonic Crystals

In this work we consider the propagation of transverse electromagnetic waves in one-dimensional photonic crystals consisting of periodic arrays of slabs. On the basis of the Floquet theory we obtain the characteristic function of the periodic medium, which defines the photonic bands of the crystal. The characteristic function is constructed from the monodromy matrices of the slabs. Entries of monodromy matrices are explicitly given as power series of the spectral parameter. The present analysis can be applied not only to homogeneous slabs, but also to slabs with varying refractive indexes. The power series representation of the entries of monodromy matrices leads to an effective numerical method for the calculation of the spectral bands of one-dimensional photonic crystals.

Control of ordinary and extraordinary waves excitation by an axial magnetic field in motional plasma

The propagation of transverse Electromagnetic (EM) waves along a high energy relativistic electron beam passing through a neutralizing heavy ion background is investigated in the presence of an external axial magnetic field. By making use of the linearized fluid equations coupled with Maxwell’s equations the dielectric tensor and the dispersion relation of excited modes are derived. Since the electron motion is considered relativistic and fluid theory of plasma is used to describe the system, the obtained results are applicable to a vast range of high energy density regime. The mutual interaction between EM and Electron Plasma Waves (EPWs) is studied numerically. In the absence of the axial magnetic field, the EPWs and the Extraordinary Electromagnetic (EOEM) waves interact due to the existence of the self-generated magnetic field. The instability caused by this interaction has already been reported [Phys. Plasma.16, 062107 (2009) ]. We found that applying an axial magnetic field will cause deflection to plasma oscillations which enables coupling between EPWs and Ordinary Electromagnetic (OEM) waves as well. The results show that increasing the external magnetic field strength suppresses the growth rate caused by the coupling of EPWs-EOEM and passes it to the growth of EPWs-OEM. Therefore by adjusting the external magnetic field strength, the growth of EOEM and OEM modes can be controlled.

Ion-scale Electromagnetic Waves in the Inner Heliosphere

Abstract Understanding the physical processes in the solar wind and corona that actively contribute to heating, acceleration, and dissipation is a primary objective of NASA’s Parker Solar Probe (PSP) mission. Observations of circularly polarized electromagnetic waves at ion scales suggest that cyclotron resonance and wave–particle interactions are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of circularly polarized events in the first perihelion encounter of PSP demonstrates that transverse electromagnetic waves at ion resonant scales are observed in 30–50% of radial field intervals. Average wave amplitudes of approximately 4 nT are measured, while the mean duration of wave events is on the order of 20 s; however, long-duration wave events can exist without interruption on hour-long timescales. Determination of wave vectors suggests propagation parallel/antiparallel to the mean magnetic field. Though ion-scale waves are preferentially observed during intervals with a radial mean magnetic field, we show that measurement constraints, associated with single spacecraft sampling of quasi-parallel waves superposed with anisotropic turbulence, render the measured coherent ion-wave spectrum unobservable when the mean magnetic field is oblique to the solar wind flow; these results imply that the occurrence of coherent ion-scale waves is not limited to a radial field configuration. The lack of radial scaling of characteristic wave amplitudes and duration suggests that the waves are generated in situ through plasma instabilities. Additionally, observations of proton distribution functions indicate that temperature anisotropy may drive the observed ion-scale waves.

On accelerative mechanism of nuclear fusion in the Sun

An explanation of an existence of sunspots on the surface of the photosphere is given. They are caused by the presence of current-plasma channels between the surplus negatively charged nucleus and the surplus positively charged photosphere of the Sun. In current-plasma channels and in prominences that appear during electrical breakdown between electric islands on the surface of the photosphere, electrical domains are generated due to presence of runaway electrons. The generation of electrical domains accompanied by the generation of transverse electromagnetic waves. Charged particles in the electromagnetic wave field gain energy that is sufficient to overcome the Coulomb potential barrier.

Influence of Inhomogeneity on Transformation and Radiation Processes in Plasma with Upper Hybrid Pump

On the basis of the kinetic theory of fluctuations, the processes of the longitudinal Langmuir wave transformation into a transverse electromagnetic wave in the turbulent inhomogeneous plasma have been studied. The plasma turbulence is assumed to arise owing to the parametric decay of the upper hybrid pump wave into a daughter wave and electron-drift oscillations. The transformation coefficient under the parametric instability saturation conditions is determined. The intensity of the electromagnetic radiation emission from the plasma is calculated, and its dependence on the plasma and pump wave parameters is found.

Co- and counter-propagating wave effects in an absorbing medium

In this semi-tutorial paper, we revisit the interference phenomena caused by pairs of co-propagating or counter-propagating transverse electromagnetic waves by letting the host medium be absorbing. We first consider plane waves in an unbounded medium, summarize the standing-wave solution of the Maxwell equations, and discuss specific effects caused by nonvanishing absorption. We then consider the superposition of plane and spherical waves in the context of far-field electromagnetic scattering by a particle. To this end we modify the classical Jones lemma by allowing nonzero absorption in the host medium and consider its most obvious consequences such as forward- and backscattering interference. The physical similarity of the two scenarios (superpositions of plane waves and superpositions of plane and spherical waves) is discussed.

Ion and Electron Dynamics in the Presence of Mirror, Electromagnetic Ion Cyclotron, and Whistler Waves

Abstract The wave–particle cyclotron interaction is a basic process in collisionless plasmas, which results in the redistribution of the energy between plasma waves and charged particles. This paper presents an event observation in order to explore the dynamics of charged particles and plasma waves, i.e., mirror, electromagnetic ion cyclotron (EMIC), and whistler waves, in the Earth’s magnetosheath. It shows that when ions have a high-speed streaming velocity parallel to the magnetic field, EMIC waves arise. We also find that the frequency distribution of nearly parallel and nearly antiparallel whistler waves depends on the parallel streaming velocity of electrons. Based on the linear kinetic theory and the fitting plasma parameters, we show that the differential flows among ion components can enhance the ion cyclotron anisotropy instability that is even stronger than the mirror instability. The differential electron flows induce an asymmetry of the growth rate of counter-propagating whistler waves in the electron cyclotron anisotropy instability. On the other hand, the low-frequency EMIC and transverse electromagnetic waves modulate the ion pitch angle distribution. Moreover, when charged particles flow across the magnetic field, both low- and high-energy electrons are deeply trapped by mirror waves. These results illustrate new features of the observed plasma waves and charged particles in the Earth’s magnetosheath, which could inspire improvement of the wave models therein.

LOSSY TRANSMISSION LINES TERMINATED BY PARALLEL CONNECTED RLC-ELEMENTS WITHOUT THE HEAVISIDE’S CONDITION

The paper deals with analysis of propagation of transverse electromagnetic waves along lossy transmission lines terminated by a circuit consisting of parallel connected RLCelements. Using the Kirchhoff’s laws we derive boundary conditions and formulate the mixed problem for hyperbolic system describing the lossy transmission line. Without the Heaviside's condition, we cannot guarantee the distortionless propagation of waves and hence we cannot apply the known methods. That is why we apply a different method and obtain conditions for existence-uniqueness of generalized solution. We change variables and formulate a mixed problem for the hyperbolic system with respect to the new variables. The nonlinear characteristics of the RLC-elements generate nonlinearity in the equations of neutral type on the boundary. We propose an operator presentation of the mixed problem for transmission line system and by means of fixed point technique we prove existence-uniqueness of a generalized solution.

LOSSY TRANSMISSION LINES TERMINATED BY PARALLEL CONNECTED RLC-ELEMENTS WITHOUT THE HEAVISIDE’S CONDITION

The paper deals with analysis of propagation of transverse electromagnetic waves along lossy transmission lines terminated by a circuit consisting of parallel connected RLCelements. Using the Kirchhoff’s laws we derive boundary conditions and formulate the mixed problem for hyperbolic system describing the lossy transmission line. Without the Heaviside's condition, we cannot guarantee the distortionless propagation of waves and hence we cannot apply the known methods. That is why we apply a different method and obtain conditions for existence-uniqueness of generalized solution. We change variables and formulate a mixed problem for the hyperbolic system with respect to the new variables. The nonlinear characteristics of the RLC-elements generate nonlinearity in the equations of neutral type on the boundary. We propose an operator presentation of the mixed problem for transmission line system and by means of fixed point technique we prove existence-uniqueness of a generalized solution.

Development of an Exactly Solvable Model of Resonance Tunneling of Electromagnetic Waves through Gradient Barriers in a Nonuniform Magnetoactive Plasma

An exactly solvable one-dimensional model describing resonance tunneling (reflectionless transmission) of a transverse electromagnetic wave through wide layers of magnetoactive plasma is developed on the basis of the Helmholtz equation. The plasma layers include a set of spatially localized density structures the amplitudes and thicknesses of which are such that approximate methods are inapplicable for their analysis. The profiles of the plasma density structures strongly depend on the choice of the free parameters of the problem that determine the amplitudes of plasma density modulation, characteristic scale lengths of the density structures, their number, and the total thickness of the nonuniform plasma layer. The plasma layers can also include a set of random inhomogeneities. The propagation of electromagnetic waves through such complicated plasma inhomogeneities is analyzed numerically within the proposed exactly solvable model. According to calculations, there are a wide set of inhomogeneous structures for which an electromagnetic wave incident from vacuum can propagate through the plasma layer without reflection, i.e., the complete tunneling of thick plasma barriers takes place. The model also allows one to exactly solve a one-dimensional problem on the nonlinear transillumination of a nonuniform plasma layer in the presence of cubic nonlinearity. It is important that, due to nonlinearity, the thicknesses of the evanescent plasma regions can decrease substantially and, at a sufficiently strong nonlinearity, such regions will disappear completely. The problem of resonance tunneling of electromagnetic radiation through gradient wave barriers is of interest for various applications, such as efficient heating of dense plasma by electromagnetic radiation and transmission of electromagnetic signals from a source located in the near-Earth plasma or deep in the plasma of an astrophysical object through the surrounding evanescent regions.

Metaparticles of Pulsed Wave Fields

Properties of elementary particles of pulsed (localized) electromagnetic and acoustic wave fields directionally radiated by aperture sources (antennas, lasers, acoustic diaphragms) in free space and homogeneous isotropic media, for which the term metaparticle is used, are considered. The structure of the wave field and the energy transferred by the metaparticles are presented. The results obtained for the presented scalar theory of metaparticles of pulsed transverse electromagnetic (TEM) waves and longitudinal elastic acoustic waves can be extended to vector pulsed wave modes guided by layered inhomogeneous guiding media and guiding technical devices (waveguides).

Pulse generation scheme for flying electromagnetic doughnuts

Transverse electromagnetic plane waves are fundamental solutions of Maxwell's equations. It is less known that a radically different type of solutions has been described theoretically, but has never been realized experimentally, that exist only in the form of short burst of electromagnetic energy propagating in free-space at the speed of light. They are distinguished from transverse waves by a donut-like configuration of electric and magnetic fields with a strong field component along the propagation direction. Here, we report that such 'Flying Donuts' can be generated from conventional pulses using a singular metamaterial converter designed to manipulate both the spatial and spectral structure of the input pulse. The ability to generate Flying Donuts is of fundamental interest, as they shall interact with matter in unique ways, including non-trivial field transformations upon reflection from interfaces and the excitation of toroidal response and anapole modes in matter, thus offering new opportunities for telecommunications, sensing, and spectroscopy.

An Effective Permittivity Tensor of Cylindrically Perforated Dielectrics

In the letter, we propose a simple analytical effective permittivity model of perforated dielectrics composed of through-hole cylindrical perforations. As the perforated dielectrics are uniaxial media, the model respects the anisotropic properties of the material and the results are simple engineering formulas for effective permittivities of ordinary and extraordinary wave for polarization corresponding to parallel and perpendicular orientation with respect to the axis of perforations. The model is based on the 2-D Maxwell Garnett approximation of inhomogeneous media valid for circularly shaped perforations. The analytical results obtained for propagation of transverse electromagnetic wave are verified by unit-cell full-wave simulations of triangular perforations lattice, and a very good agreement is obtained.

Terahertz emission from the intrinsic Josephson junctions of high-symmetry thermally-managed Bi2Sr2CaCu2O8+δ microstrip antennas

We show for high-symmetry disk, square, or equilateral triangular thin microstrip antennas of any composition respectively obeying C∞v, C4v, and C3v point group symmetries, that the transverse magnetic electromagnetic cavity mode wave functions are restricted in form to those that are one-dimensional representations of those point groups. Plots of the common nodal points of the ten lowest-energy non-radiating two-dimensional representations of each of these three symmetries are presented. For comparison with symmetry-broken disk intrinsic Josephson junction microstrip antennas constructed from the highly anisotropic layered superconductor Bi2Sr2CaCu2O8+δ (BSCCO), we present plots of the ten lowest frequency orthonormal wave functions and of their emission power angular distributions. These results are compared with previous results for square and equilateral triangular thin microstrip antennas.

Optical characteristics of finite temperature quantum electron gas

In this paper we study the propagation of elliptically polarized transverse electromagnetic waves in a quasineutral plasma with arbitrary degenerate electron fluid ranging from classical dilute to fully degenerate density regimes by using the appropriate collisional magnetohydrodynamics model, which incorporates the adiabatic quantum equation of states for high-frequency electron fluid compression and the Bohm quantum potential responsible for the collective quantum diffraction effect. Three distinct propagation modes are categorized corresponding to electron density regimes of dilute, intermediate, and fully degenerate plasmas. One of these modes is found to be purely of quantum mechanical origin and disappears in the absence of the quantum diffraction effect. The present generalized magnetohydrodynamics theory qualitatively describes key features of optical parameters and experimental data of dilute classical, semiconducting, and in fully degenerate plasmas. Different optical parameters, such as the refractive and absorption index of the new mode are investigated. It is shown that the optical response of the magnetized plasma with arbitrary degeneracy is essentially governed by three characteristic frequencies, namely, collision, plasmon, and cyclotron frequencies. The profound experimental minimum in the refractive index of arbitrary degenerate quantum plasmas and its dependence on the characteristic frequencies is studied in detail. Current investigation is of fundamental importance in high energy density and fusion plasma diagnostics and may provide key knowledge on the characteristics of astrophysical dense matter.