scholarly journals Modulation of Ion and Electron Pitch Angle in the Presence of Large-amplitude, Low-frequency, Left-hand Circularly Polarized Electromagnetic Waves Observed by MMS

2018 ◽  
Vol 867 (1) ◽  
pp. 58 ◽  
Author(s):  
J. S. Zhao ◽  
T. Y. Wang ◽  
M. W. Dunlop ◽  
J. S. He ◽  
X. C. Dong ◽  
...  
Keyword(s):  
Large Amplitude ◽  
Pitch Angle ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Circularly Polarized ◽  
Left Hand

scholarly journals Numerical study of upper hybrid to <i>Z</i>-mode leakage during electromagnetic pumping of groups of striations in the ionosphere

2015 ◽  
Vol 33 (8) ◽  
pp. 1019-1030 ◽  
Author(s):  
B. Eliasson ◽  
T. B. Leyser
Keyword(s):  
High Frequency ◽  
Large Amplitude ◽  
Electromagnetic Waves ◽  
Ionospheric Plasma ◽  
Numerical Study ◽  
Lower Hybrid ◽  
Loss Mechanism ◽  
Circularly Polarized ◽  
Left Hand ◽  
Mode Wave

Abstract. We investigate numerically the interaction between ionospheric magnetic field-aligned density striations and a left-hand circularly polarized (L)-mode wave. The L-mode wave is scattered into upper hybrid (UH) waves which are partially trapped in the striations, but leak energy to electromagnetic waves in the Z-mode branch. For small-amplitude (1 %) striations, this loss mechanism leads to a significant reduction in amplitude of the UH waves. For several striations organized in a lattice, the leaking of Z-mode waves is compensated by influx of Z-mode radiation from neighboring striations, leading to an increased amplitude of the weakly trapped UH waves. For large-amplitude (10 %) striations the trapped UH waves rapidly increase in amplitude far beyond the threshold for parametric instabilities, and the Z-mode leakage is less important. The results have relevance for the growth of striations and the onset of UH and lower hybrid turbulence during electromagnetic high-frequency pumping of ionospheric plasma, which require large-amplitude UH waves.

scholarly journals WAVEGUIDE FEED NETWORK FOR HORN ANTENNA WITH CIRCULAR POLARIZATION

2021 ◽  
Author(s):  
Stepan Piltyay
Keyword(s):  
Circular Polarization ◽  
Electromagnetic Waves ◽  
Metal Structure ◽  
Horn Antenna ◽  
Variable Cross ◽  
Circularly Polarized ◽  
Maximum Gain ◽  
Left Hand ◽  
Right Hand ◽  
Feed Network

The article presents the methodology for designing and optimizing of feed network for a circularly polarized horn antenna. A horn antenna has a metal structure and consists of a waveguide that has a variable cross-section and an open radiating end. Electromagnetic waves in such antenna are excited by a waveguide that is connected to a horn antenna in through the narrow wall. The proposed feed network of the horn antenna consists of a rectangular waveguide with a slot. In order to obtain the excitation of signals with circular polarization at the output, a slot was cut in the waveguide at an angle of 45º. As a result, the network makes it possible to form the signals with right-hand circular polarization and left-hand circular polarization. The presented design of the horn antenna feed network eliminates the need to develop a separate waveguide device of polarization processing. The designed feed network of the circularly polarized horn antenna can be used at an operating frequency of 8.0 GHz. At these frequency the reflection coefficient is less than −19 dB. The proposed horn antenna provides a maximum gain of 21 dB for right-hand circular polarization and a maximum gain of 10 dB for left-hand circular polarization. Cross-polarization isolation is higher than 10 dB. Therefore, the developed feed network of the horn antenna provides narrowband operating mode at the circular polarization with satisfying electromagnetic polarization characteristics and matching at the frequency of 8 GHz. Developed feed network of the horn antenna with circular polarization can be used in radio engineering systems, which carry out polarization processing of signals.

Large-amplitude circularly polarized electromagnetic waves in magnetized plasma

2014 ◽  
Vol 21 (5) ◽  
pp. 054501 ◽  
Author(s):  
I. Y. Vasko ◽  
A. V. Artemyev ◽  
L. M. Zelenyi
Keyword(s):  
Large Amplitude ◽  
Electromagnetic Waves ◽  
Magnetized Plasma ◽  
Circularly Polarized

Singularities in the transverse fields of electromagnetic waves. II. Observations on the electric field

1987 ◽  
Vol 414 (1847) ◽  
pp. 447-468 ◽  
Keyword(s):  
Electric Field ◽  
Free Space ◽  
Electromagnetic Waves ◽  
Structural Features ◽  
Circularly Polarized ◽  
Left Hand ◽  
Right Hand ◽  
Transverse Fields

Electromagnetic waves propagating in free space contain three kinds of singularities called C lines, S surfaces and disclinations. The paper describes observations of these singularities in two different mono-chromatic microwave fields. The observations confirm all the theor­etically predicted properties of the singularities that could be tested. As expected, the singularities were found to be prominent structural features of the fields and in consequence to provide an economical means of characterizing their structure. A notable result is the observation of both right-hand and left-hand C lines in a field that is nominally uniformly left-hand circularly polarized. This is in agreement with the previous assertion that, in general, electromagnetic wavefields contain both right-hand and left-hand polarized regions.

Acceleration of charged particles by large-amplitude electromagnetic waves

1994 ◽  
Vol 52 (2) ◽  
pp. 339-342 ◽  
Author(s):  
S. P. Kuo ◽  
M. C. Lee
Keyword(s):  
Lorentz Force ◽  
Analytical Solutions ◽  
Large Amplitude ◽  
Electromagnetic Waves ◽  
Charged Particles ◽  
Wave Fields ◽  
Circularly Polarized ◽  
Exact Analytical Solutions ◽  
Fundamental Process ◽  
Low Energies

The fundamental process of acceleration of charged particles by large-amplitude electromagnetic waves is investigated. Exact analytical solutions can be derived from the nonlinear equations that govern the motion of charged particles in wave fields. It is found that circularly polarized electromagnetic waves can act on the charged particles via α d.c. Lorentz force imposed by the wave fields. This process can effectively energize charged particles that may initially have low energies.

scholarly journals Geometric phase for multidimensional manipulation of photonics spin Hall effect and helicity-dependent imaging

Nanophotonics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1501-1508 ◽  
Author(s):  
XiaoFei Zang ◽  
BingShuang Yao ◽  
Zhen Li ◽  
Yang Zhu ◽  
JingYa Xie ◽  
...  
Keyword(s):  
Hall Effect ◽  
Geometric Phase ◽  
Electromagnetic Waves ◽  
Spin Hall Effect ◽  
Spin States ◽  
Terahertz Waves ◽  
Circularly Polarized ◽  
Left Hand ◽  
Terahertz Region ◽  
Spin Orbit Interactions

AbstractThe spin Hall effect of light, associated with spin-orbit interactions, describes a transport phenomenon with optical spin-dependent splitting, leading to a plethora of applications such as sensing, imaging, and spin-controlled nanophotonics. Although geometric meatsurfaces can mimic photonic spin Hall effect by spatially splitting left-hand circularly polarized and right-hand circularly polarized states of electromagnetic waves with anomalous refraction or reflection angles, the geometric phase generated by metasurfaces hinders metalenses to realize simultaneous focusing of different spin states, limiting further applications. Here, we propose and experimentally demonstrate an approach to realizing a spin Hall metalens that can focus terahertz waves with different spin states and flexibly manipulate spin-dependent focal points in multiple spatial dimensions based on a pure geometric phase. A dielectric metasurface consisting of micropillars with identical shape and different in-plane orientations is designed to realize the multidimensional manipulation of photonics spin Hall effect in terahertz region. Furthermore, helicity-dependent imaging is demonstrated by the terahertz spin Hall metalens. The uniqueness and robust approach for manipulating spin photons may have a significant impact on designing ultra-compact and multifunctional devices and spin photonics devices.

scholarly journals Strong Waves from Pulsars and Morphologies in SNRs

1983 ◽  
Vol 101 ◽  
pp. 499-501
Author(s):  
Gregory Benford ◽  
Attilio Ferrari ◽  
Silvano Massaglia
Keyword(s):  
Large Amplitude ◽  
Crab Nebula ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Optical Emission ◽  
Amplitude Wave ◽  
Surface Magnetic Field ◽  
Plasma Absorption ◽  
The Crab Nebula ◽  
Large Amplitude Wave

Canonical models for pulsars predict the emission of low–frequency waves of large amplitudes, produced by the rotation of a neutron star possessing a strong surface magnetic field. Pacini (1968) proposed this as the basic drain which yields to the pulsar slowing–down rate. The main relevance of the large amplitude wave (LAW) is the energetic link it provides between the pulsar and the surrounding medium. This role has been differently emphasized (Rees and Gunn, 1974; Ferrari, 1974), referring to absorption effects by relativistic particle acceleration and thermal heating, either close to the pulsar magnetosphere or in the nebula. It has been analyzed in the special case of the Crab Nebula, where observations are especially rich (Rees, 1971). As the Crab Nebula displays a cavity around the pulsar of dimension ∼1017cm, the function of the wave in sweeping dense gas away from the circumpulsar region is widely accepted. Absorption probably occurs at the inner edges of the nebula; i.e., where the wave pressure and the nebular pressure come into balance. Ferrari (1974) interpreted the wisps of the Crab Nebula as the region where plasma absorption occurs, damping the large amplitude wave and driving “parametric” plasma turbulence, thus trasferring energy to optical radiation powering the nebula. The mechanism has been extended to interpret the specific features of the “wisps” emission (Benford et al., 1978). Possibly the wave fills the nebula completely, permeating the space outside filaments with electromagnetic energy, continuously accelerating electrons for the extended radio and optical emission (Rees, 1971).

Bilayer split-ring chiral metamaterial based reconfigurable antenna for polarization conversion

Frequenz ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Preet Kaur ◽  
Pravin R. Prajapati
Keyword(s):  
Low Cost ◽  
Axial Ratio ◽  
Center Frequency ◽  
Impedance Bandwidth ◽  
Split Ring ◽  
Circularly Polarized ◽  
Left Hand ◽  
Rectangular Patch ◽  
Mode 2 ◽  
Chiral Metamaterial

Abstract A bilayer split-ring chiral metamaterial converts the linearly polarized wave, into a nearly perfect left or right-handed circularly polarized wave. The proposed antenna is intended to operate at center frequency of 5.80 GHz with switchable polarization capability. The polarization re-configurability is achieved by electronically switching of two PIN-diode pairs, which are embedded into bilayer split-ring Chiral Metamaterial. The optimized length of rectangular patch is 16 mm and width is 12.1 mm. Two types of radiation characteristics offered by the proposed antenna; left hand circularly polarized in mode 1 and right hand circularly polarized in mode 2. Measured results show that its impedance bandwidth is 155 MHz from 5.70 to 5.855 GHz for both mode 1 and mode 2. The measured axial-ratio bandwidth is 100 MHz from 5.75 to 5.85 GHz for mode 1 and 110 MHz from 5.73 to 5.84 GHz for mode 2. Antenna has LHCP gain of 2.52 dBi and RHCP gain of −23 dBi in mode 1. RHCP gain of 2 dBi and polarization purity of about −20 dBi is obtained in mode 2. The proposed antenna has simple structure, low cost and it has potential application in field of wireless communication (i.e., WiMax, WLAN etc.).

Multiple-S-Shaped Critical Manifold and Jump Phenomena in Low Frequency Forced Vibration with Amplitude Modulation

2019 ◽  
Vol 29 (05) ◽  
pp. 1930012 ◽  
Author(s):  
Yue Yu ◽  
Qianqian Wang ◽  
Qinsheng Bi ◽  
C. W. Lim
Keyword(s):  
Amplitude Modulation ◽  
Large Amplitude ◽  
Low Frequency ◽  
Slow Variable ◽  
Critical Manifold ◽  
Singular Orbit ◽  
Modulation Control ◽  
Cycle Oscillation ◽  
Tuning Frequency ◽  
Complex Mechanical Systems

Motivated by the forced harmonic vibration of complex mechanical systems, we analyze the dynamics involving different waves in a double-well potential oscillator coupling amplitude modulation control of low frequency. The combination of amplitude modulation factor significantly enriches the dynamical behaviors on the formation of multiple-S-shaped manifold and multiple jumping phenomena that alternate between epochs of slow and fast motion. We can conduct bifurcation analysis to identify two harmonic vibrations. One is that the singular orbit makes multiple jumps to a fast trajectory segment from one attracting equilibrium to another as the expression of slow variable by using the DeMoivre formula. With the increase of tuning frequency, the system exhibits relaxation-type oscillations whose small amplitude oscillations are produced by nonlinear local cycles together with a distinct large amplitude cycle oscillation accounting for the Melnikov threshold values. The tuning frequency may not only affect the asymptotic expressions for the solution curves near fold singularities but also allow for the large amplitude orbit vibrations near fold-cycle singularities. Numerical analysis for computing critical manifolds and their intersections is used to detect the dynamical features in this paper.

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