Propagation Of Extraordinary Waves Research Articles

Locally resonant metamaterials utilizing dynamic directional amplification: An application for seismic mitigation

Locally resonant metamaterials (LRMs), with unit-cells exhibiting local resonance, present extraordinary wave propagation properties as a result of their spatial periodicity. However, these structures present certain limitations when wide bandgaps are sought, such as the need of heavy resonating masses. In this paper, a simple dynamic directional amplification (DDA) mechanism is proposed as a means to artificially increase inertia of the resonating mass. The DDA is realized by imposing kinematic constraints to the model's degrees of freedom (DoFs), hence inertia is increased by coupling the horizontal and vertical motion of a reference two-dimensional (2D) mass-in-mass lattice. A discrete element lattice model based on mass, stiffness, and damping elements, is used to establish dispersion behavior and frequency response, while results indicate broader bandgaps and significant improvements compared to the reference LRM. At last, a preliminary design of a DDA-metabarrier is presented as a proof of concept, showcasing the potential application of the mechanism as a seismic wave mitigation measure.

Extraordinary and upper-hybrid waves in spin quantum magnetoplasmas with vacuum polarization effect

The propagation of extraordinary and upper-hybrid waves in spin quantum magnetoplasmas with vacuum polarization effect is investigated. Based on the quantum magnetohydrodynamics model including Bohm potential, arbitrary relativistic degeneracy pressure and spin force, and Maxwell's equations modified by the spin current and vacuum polarization current, the dispersion relations of extraordinary and upper-hybrid waves are derived. The analytical and numerical results show that quantum effects (Bohm potential, degeneracy pressure and spin magnetization energy) and the vacuum polarization effect modify the propagation of the extraordinary wave. Under the action of a strong magnetic field, the plasma frequency is obviously increased by the vacuum polarization effect.

Elliptically polarized electromagnetic waves in a magnetized quantum electron-positron plasma with effects of exchange-correlation

The dispersion properties of elliptically polarized electromagnetic waves in a magnetized electron-positron-pair (EP-pair) plasma are studied with the effects of particle dispersion associated with the Bohm potential, the Fermi degenerate pressure, and the exchange-correlation force. Two possible modes of the extraordinary or X wave, modified by these quantum effects, are identified and their propagation characteristics are investigated numerically. It is shown that the upper-hybrid frequency and the cutoff and resonance frequencies are no longer constants but are dispersive due to these quantum effects. It is found that the particle dispersion and the exchange-correlation force can have different dominating roles on each other depending on whether the X waves are of short or long wavelengths (in comparison with the Fermi Debye length). The present investigation should be useful for understanding the collective behaviors of EP plasma oscillations and the propagation of extraordinary waves in magnetized dense EP-pair plasmas.

Dynamic regimes of cyclotron instability in the afterglow mode of minimum-B electron cyclotron resonance ion source plasma

The paper is concerned with the dynamic regimes of cyclotron instabilities in non-equilibrium plasma of a minimum-B electron cyclotron resonance ion source operated in pulsed mode. The instability appears in decaying ion source plasma shortly (1–10 ms) after switching off the microwave radiation of the klystron, and manifests itself in the form of powerful pulses of electromagnetic emission associated with precipitation of high-energy electrons along the magnetic field lines. Recently it was shown that this plasma instability causes perturbations of the extracted ion current, which limits the performance of the ion source and generates strong bursts of bremsstrahlung emission. In this article we present time-resolved diagnostics of electromagnetic emission bursts related to cyclotron instability in the decaying plasma. The temporal resolution is sufficient to study the fine structure of the dynamic spectra of the electromagnetic emission at different operating regimes of the ion source. It was found that at different values of magnetic field and heating power the dynamic spectra demonstrate common features: Decreasing frequency from burst to burst and an always falling tone during a single burst of instability. The analysis has shown that the instability is driven by the resonant interaction of hot electrons, distributed between the electron cyclotron resonance (ECR) zone and the trap center, with slow extraordinary wave propagation quasi-parallel with respect to the external magnetic field.

The effect of the electron sound speed on wave propagation in the ionospheric plasma

In this study, the effect of the electron sound speed on the extraordinary wave propagation is calculated without an approximation for either collisional or collisionless cases in the ionospheric plasma by using the real geometry of the Earth’s magnetic field for the Northern Hemisphere. It is observed that there is no remarkable effect on the propagation of the extraordinary wave, especially at reflection altitudes. But it is also observed that the magnitudes of k2 (the square of the wave number) have changed every season, and the phase velocity of wave in warm ionospheric plasma has increased.

Optical breathers in uniaxial crystals

Anisotropic crystals are shown to have three different mechanisms of the formation of breathers depending on the direction of the extraordinary wave propagation and on the symmetry of the medium. All uniaxial crystals with quadratic susceptibilities can be divided into three different groups, according to the crystal classes (CC). Each group is characterized by a universal structure of the breather zones (SBZ). The SBZ of the media with cubic susceptibilities does not depend neither on the crystal systems nor on the CC and coincides with the SBZ of the crystals with quadratic susceptibilities and the CC 3, 3m, 4, 4mm, 6, 6mm.

An approximate theory of electromagnetic wave propagation in a weakly relativistic plasma

An approximate analysis of different types of electromagnetic wave propagation in a weakly relativistic electron plasma is presented. The particular case of wave propagation near the cold plasma cut-offs is considered, and possible applications of the results to diagnostics of magnetospheric parameters are discussed. It is pointed out that wave propagation near plasma resonances in some cases requires relativistic consideration, especially for extraordinary waves. Almost parallel right- and left-hand polarized waves as well as almost perpendicular ordinary and extraordinary wave propagation are considered in detail. It is shown that, in the vicinity of certain frequencies, relativistic effects on the refractive index of these waves cannot be disregarded even when the electron energy is quite small. The problem of wave energy focusing along and perpendicular to the magnetic field is considered with relativistic effects taken into account.

Wave Propagation in Layered-Inhomogeneous Planar Anisotropic Media: Geometrical-Optics Approximation and Its Application

Abstract The geometrical-optics approximation for describing the propagation of extraordinary waves in layered-inhomogeneous planar anisotropic media can be expressed as a series of laws. The results are applied to study the optical properties of spatially, inhomogeneous nematic liquid crystal structures.

Observation of extraordinary wave propagation near the lower hybrid resonance frequency

Measurements of k ⊥ for an extraordinary wave near the lower hybrid frequency have been carried out by means of propagation between two dipole antennas into a plasma column. Resonance-like behavior have been observed when plasma parameters and frequency fulfil the condition ω ≈ ω LH.

Cyclotron Harmonic Resonances in an Electrodeless Discharge

Electron-cyclotron harmonic resonances in rf-excited, electrodeless, helium discharges have been investigated experimentally. The discharge simulates a plasma slab of relatively uniform electron density in a uniform magnetic field. Measurements were made at 9.15 GHz of both incoherent emission and coherent fundamental wave propagation, the microwaves propagating in a direction perpendicular to the magnetic field and normal to the slab boundaries. Emission resonances were found for both ordinary and extraordinary wave propagation. Precise measurements of the magnetic field at corresponding peaks for the ordinary and extraordinary waves show that the former occur at magnetic fields about 0.3% lower than that of the latter, independent of harmonic number, electron density and pressure. The ordinary wave resonances occur at the cyclotron harmonic within experimental error (0.1%). Resonances were found in the coherent fundamental transmitted and reflected waves and are due to resonance absorption. Their magnetic field positions always occur on the high magnetic field side of the cyclotron harmonic (by as much as 2.5%).