Sense Of Polarization Research Articles

Properties of individual S-bursts observed in the frequency band of 10–32 MHz during the rising phase of 25-th solar cycle

Introduction: The properties of the S-bursts observed during the storm on 20–21 June 2022 in frequency band 10–32 MHz by the radio telescope URAN-2 are discussed in this paper. The storm was highly populated with other solar bursts, such as Type III bursts and drift pairs. The occurrence rate of S-bursts was very high reaching 60 bursts per minute. All observed S-bursts were characterized by low fluxes with respect to the background radio emission. Thus special processing methods are used to retrieve spectral properties of the bursts. Some individual “long” S-bursts covered the whole frequency band of the URAN-2 radio telescope from 10 to 32 MHz. Such extended in frequency S-bursts were recorded for the first time. 50 extended S-bursts were selected for the further analysis.Methods: The S-bursts dynamic spectra with time-frequency resolutions of 100 ms and 4 kHz as well as single-frequency profiles were used in the analysis. Due to low S-bursts intensities the drift rates were estimated from the time-differentiated dynamic spectra, highlighting the tracks of the bursts maxima. Polarization dynamic spectra were used for measuring the degree and sense of the S-bursts circular polarization. Individual S-bursts tracks were used for instant coronal inhomogeneities diagnostics. Mean S-bursts parameters retrieved from the statistical processing of the set of 50 bursts were compared with previously obtained ones.Results: We concluded that by the mean durations, drift rates, frequency extent and the polarization all observed S-bursts could be divided into two separate groups, the “short” and the “long” S-bursts. The power-law index of the drift rate-frequency dependence averaged over all 50 selected bursts was found to be 1.7. It was shown that sources of S-bursts most likely move through the Newkirk corona with the velocities of 0.06–0.08c. The power-law dependence of the “long” S-bursts durations on frequency in frequency band of 12–30 MHz was obtained. Its index equal to −0.61 appeared to be very close to that for Type III bursts. From this dependence the electron velocity dispersion in the beam, responsible for S-bursts generation was calculated. Its value of 0.02 indicates that the beams, responsible for S-bursts generation are almost monoenergetic.Discussion: It is assumed that non-monotonic appearance of individual S-bursts tracks on the dynamic spectrum reflects density inhomogeneities encountered by the sources on their paths. From the dynamic spectra of such S-bursts the characteristic size and amplitude of these coronal inhomogeneities were detected. From the S-bursts durations and the velocities of their sources the longitudinal sizes of the latter were estimated. It was then shown that the sizes of small-scale coronal inhomogeneities were comparable to those of “long” S-bursts sources. Thus we concluded that individual tracks of the “long” S-bursts can be used for fie diagnostics the coronal plasma at heliocentric heights range from 1.7 to 3.2 Rs, where Rs is the solar radius. On the other hand, these tracks being ensemble-averaged give the information about the long-term large scale properties of the corona.

Generalized neutral axes in nondepolarizing optical systems.

The polarizing properties of optical systems are often characterized by their action on specific polarization states. For example, half-wave plates are used to rotate linear polarizations and quarter-wave plates to turn a linear polarization into an elliptical polarization and into a circular polarization if the linear polarization makes a 45° angle with the slow and fast axes of the quarter-wave plate. Phase shifts introduced by the optical train of an interferometer may lead to coherence losses and the existence of neutral axes-in the sense of linear polarizations whose polarization state is not modified by the optical system-is then of importance to maximize the fringe contrast. Neutral axes do not systematically exist. The purpose of this paper is to investigate how this notion can be generalized to define generalized neutral axes for optical systems. Generalized neutral axes are defined as linear polarizations whose polarization state is not modified by the optical system except for their orientation. It is shown that such generalized neutral axes exist for some classes of optical systems. The scheme proposed in this paper has quasi-unitary Jones matrices to give an approximate description of optical systems when generalized neutral axes do not exist. To the best of my knowledge, this formalism is a new scheme to describe the polarizing properties of nondepolarizing optical systems.

Solar Radio Spectro-polarimeter (50–500 MHz). I. Design, Development, and Characterization of a Cross-polarized, Log-periodic Dipole Antenna

The Zeeman effect has been routinely used to image and quantify the solar photospheric magnetic field (B). Such a direct measuring technique is not yet available for the corona (Lin et al. 2004). Since almost all transient nonthermal radio emissions from the corona are either partially or fully circularly polarized, observing their polarization signatures over broad frequency ranges would be of help to estimate B as a function of heliocentric height. This article aims to describe the design and development of a Cross-polarized Log-Periodic Dipole Antenna (CLPDA), an integral part of a radio spectro-polarimeter, which works in the 50–500 MHz frequency-range and to explain the tests that were carried out to characterize it. The above frequency range corresponds to a heliocentric height range ≈1.03 < r < 2.5 R ⊙ (R ⊙ = photospheric radius), wherein the numerous coronal nonthermal transients associated with space-weather effects are observed to originate. The CLPDA is used to determine the strength and sense of polarization of the received radio signal. The uncertainty involved in the determination depends on the polarization-isolation (PI) between the two orthogonal components of a CLPDA. Some of the recent advancements made in the antenna design concepts at high frequencies (∼GHz) were adopted to reduce the PI at low frequencies (∼MHz). Throughout the above frequency range, the CLPDA has a gain, return loss, and PI of ≈6.6 dBi, ≲−10 dB, and ≲−27 dB, respectively. The average PI of the CLPDA varies from −30 to −24 dB over an azimuthal angle range 0° to ±45° within which the observations are performed regularly.

Bidirectional circularly polarized antenna with defected ground structure for wideband operation

The present work proposes a wideband circularly polarized antenna with novel design to cover the operation over most of the X-band of the microwave frequencies. This antenna is planar and printed on very thin and flexible Rogers’ substrate of material RO3003 with thickness 0.13mm. The antenna structure can be viewed as composed of an elliptic open annular strip that works as the main radiator. Two symmetric parasitic elements of elliptic arc-shaped narrow strips are capacitively coupled to the elliptic strip radiator. The feeding line is coplanar waveguide with defected ground structure. The parasitic elements and the defects on the ground structures help to enhance the bandwidth of both impedance matching and circular polarization. The antenna is designed to produce bidirectional radiation patterns with opposite sense of circular polarization. The design stages to arrive at the final design of the proposed antenna are described in detail. The antenna is fabricated for experimental assessment showing high performance regarding the circular polarization, bandwidth, and efficiency. The proposed antenna has total dimensions of 30×40×0.13mm3. Both the simulation and experimental results show that the antenna impedance is matched to 50Ω over the frequency band 7.5-13.0(54%bandwidth) and the axial ratio is lower than 3 dB over the frequency band 8.85-12.35GHz(33 % bandwidth). It is shown that the antenna gain ranges from 4.5 to 5 dBi, the radiation efficiency is greater than 99 % and the total efficiency is greater than 91 % over the entire frequency band of the proposed antenna.

Contending With Polarization in the Expanding Scope of Psychotherapy.

The author queried 32 colleagues about their sense of polarization in the field of psychotherapy, using as an example the contrast between generalists (like himself) and specialists. This query was inspired by the proliferation of brands of psychotherapy coupled with the dominance of cognitive-behavioral therapies. His key conclusions: (a) tensions in the field are associated with a multitude of polarities and individual differences; (b) it is folly to reduce polarization to any single polarity; and (c) given the field's huge diversity, we are all specialists. While the author advocates greater integration of theories and methods, he also argues for expansion by including ethical thought into the scientific zeitgeist. He proposes skill in being human as a broad aspiration for therapists and patients.

Algorithm Optimization for Rockfalls Alarm System Based on Fiber Polarization Sensing

Algorithm Optimization for Rockfalls Alarm System Based on Fiber Polarization Sensing

MULTISTABILITY IN A CHIRAL SEMICONDUCTOR MICROCAVITY

The features of the bi- and multistability effects in the semiconductor Bragg microcavity with chiral photonic crystal slab on the upper mirror are investigated theoretically. It is shown that the response of such a chiral structure under a linearly polarized coherent resonant pump demonstrates sharp multistable transitions with abrupt jumps of the exciton intensity and degree of circular polarization. It is shown that of the thresholds of bistable transitions in the system with different sense of circular polarization differ slightly, i.e. in case of a non-optimized structure, we can expect to obtain even a larger amplitude of the jumps of the degree of circular polarization of the excitonic response due to the multistability than in a specially optimized chiral structure with a high degree of circular polarization at low pump intensity.

Mechanically Tunable Terahertz Circular Polarizer with Versatile Functions

AbstractCircular polarizers that selectively transmit only one handedness of circular polarization are useful for imaging and wireless communications. Conventional circular polarizers involve 3D chiral structures, which impose fabrication challenges, while typically introducing chirality within a limited bandwidth. To overcome the limitations associated with conventional non‐planar designs, a three‐layer metasurface‐based planar circular polarizer exhibiting strong and broadband chirality is presented here. Its superiority over existing multilayer designs is derived from a systematic design procedure. Measurement results reveal that the proposed structure maintains a 15‐dB extinction ratio from 251 to 293 GHz for the preferred handedness of circular polarization, leading to a fractional bandwidth of 15.4% with a transmission efficiency above 92.7%. Furthermore, the proposed structure is mechanically tunable to alter its functionality or operation bandwidth. Specifically, through simply rotating the top or bottom metallic layer by 90°, the structure can function as a transmissive quasi‐half‐wave plate that reverses the sense of circular polarization. Moreover, the presented structure can operate at nearby frequency ranges for the aforementioned functionalities by mechanically adjusting the air gap spacings between the metallic layers. Further calculations based on the measured results of each layer suggest that the proposed structure is robust to deviations in the air gap spacings.

Demonstration of high sensitivity of microwave-induced resistance oscillations to circular polarization

We demonstrate that long-debated immunity of microwave-induced resistance oscillations (MIRO) to the sense of circular polarization is not a generic property of this phenomenon in solid-state two-dimensional electron systems. Using a large-area GaAs-based heterostructure we detect up to 30 times larger MIRO signal for the cyclotron resonance (CR) active helicity, fully consistent with the concurrently measured transmission and the deduced CR shape of the Drude absorption. We further elaborate conditions to avoid extrinsic factors capable of producing an apparent immunity of the photoresponse.

Synthesis of multi-band reflective polarizing metasurfaces using a generative adversarial network

Electromagnetic linear-to-circular polarization converters with wide- and multi-band capabilities can simplify antenna systems where circular polarization is required. Multi-band solutions are attractive in satellite communication systems, which commonly have the additional requirement that the sense of polarization is reversed between adjacent bands. However, the design of these structures using conventional ad hoc methods relies heavily on empirical methods. Here, we employ a data-driven approach integrated with a generative adversarial network to explore the design space of the polarizer meta-atom thoroughly. Dual-band and triple-band reflective polarizers with stable performance over incident angles up to and including 30°, corresponding to typical reflector antenna system requirements, are synthesized using the proposed method. The feasibility and performance of the designed polarizer is validated through measurements of a fabricated prototype.

Reliable control of magnetic vortex chirality in asymmetrically optimized magnetic nanodisk

Magnetic vortex has attracted attention in the field of information storage because their topological spin structures with chiral bistable states. If the vortex core polarity and vortex circulation sense can be controlled simultaneously in a nanodisk, which will be more beneficial to realize the multi-bit ultrahigh density storage. In this paper, a reliable control scheme for magnetic vortex chirality is proposed by optimizing the structure of Pac-Man-like nanodisk. The results show that the polarity and circulation of the vortex can be controlled simultaneously by changing the direction of the global magnetic field, and even the chiral states of the vortex can be determined by detecting the stray field distribution on the surface of the nanodisk. The optimized Pac-Man-like nanodisk provide an experimental method for the control and detection of magnetic vortex chirality, which will be beneficial to the realization of multi-bit magnetic storage or magnetic logic technology in the future.

Calibration by Air in Polarization Sensing

Scattered light polarization serves as an indicator and a characteristic of various processes in the atmosphere. The polarization measurements of all scattering matrix elements provide an adequate description of the optical and morphological parameters and orientation of particles in clouds. In this article, we consider the problem of the calibration of matrix polarization lidar (MPL) parameters. Calibration by air is an effective alternative to the technique for correcting optical element parameters and among the calibration parameters of the MPL optical path are the relative transmission coefficient of a two-channel receiver, the angular positions of the transmission axes of the optical elements of the transmitter and receiver units, including the polarizers and wave plates, and the retardance of wave plates. For the first time, the method of calibration by air was partially implemented in the MPL to study Asian dust in the atmosphere. We considered the calibration problem more generally and this was due to the need to calibrate different MPL modifications from stationary to mobile ones. The calibration equations have been derived in terms of instrumental vectors, and the method of their solution by the generalized least squares method has been proposed. The method has been verified on a numerical MPL model and validated using MPL measurements in Daejeon, Republic of Korea.

Multi-band different polarized monopole antenna with modified ground for WLAN & Wi-MAX applications

ABSTRACT This paper presents the design and analysis of a multi-band, dual-polarised monopole antenna consisting of a simple equilateral triangular monopole patch configured with a modified ground structure (MGS). In the presented antenna design, quad-band dual-polarised operation has been obtained by creating the three unequal rectangular slots on the ground structure. The proposed monopole antenna produces four individual frequency bandwidths with the dual sense of polarisation, namely linear polarisation (LP) and circular polarisation (CP). The antenna produces quad-band behaviour with linear wave polarisation in Band1, whereas right-hand circular polarisation (RHCP) in rest frequency bands viz. Band2, Band3, and Band4. The measured impedance bandwidths spread from 2.50 to 4.42 GHz in band2; 5.22 to 6.28 GHz in band3; and 8.40 to 10.30 GHz in band4; whereas the impedance bandwidth extends from 1.35 to 2.14 GHz in linearly polarised band 1. The measured axial ratio bandwidth (ARBW) extends from 2.82 to 3.20 GHz in band2; 5.17 to 5.94 GHz in band3; and 9.30 to 9.70 GHz in band4, respectively. The constant gain profile has been observed in all frequency bands. The proposed antenna can be applied for WLAN/ WiMAX and Wi-Fi applications.

Synthetic solar cycle for active regions violating the Hale’s polarity law

ABSTRACTLong observational series for bipolar active regions (ARs) provide significant information about the mutual transformation of the poloidal and toroidal components of the global solar magnetic field. The direction of the toroidal field determines the polarity of leading sunspots in ARs in accordance with the Hale’s polarity law. The vast majority of bipolar ARs obey this regularity, whereas a few per cent of ARs have the opposite sense of polarity (anti-Hale ARs). However, the study of these ARs is hampered by their poor statistics. The data for five 11-yr cycles (16–18 and 23, 24) were combined here to compile a synthetic cycle of unique time length and latitudinal width. The synthetic cycle comprises data for 14838 ARs and 367 of them are the anti-Hale ARs. A specific routine to compile the synthetic cycle was demonstrated. We found that, in general, anti-Hale ARs follow the solar cycle and are spread throughout the time-latitude diagram evenly, which implies their fundamental connection with the global dynamo mechanism and the toroidal flux system. The increase in their number and percentage occurs in the second part of the cycle, which is in favour of their contribution to the polar field reversal. The excess in the anti-Hale ARs percentage at the edges of the butterfly diagram and near an oncoming solar minimum (where the toroidal field weakens) might be associated with the strengthening of the influence of turbulent convection and magnetic field fluctuations on the arising flux tubes. The evidence of the misalignment between the magnetic and heliographic equators is also found.

MHD and Ion Kinetic Waves in Field-aligned Flows Observed by Parker Solar Probe

Abstract Parker Solar Probe (PSP) observed predominately Alfvénic fluctuations in the solar wind near the Sun where the magnetic field tends to be radially aligned. In this paper, two magnetic-field-aligned solar wind flow intervals during PSP’s first two orbits are analyzed. Observations of these intervals indicate strong signatures of parallel/antiparallel-propagating waves. We utilize multiple analysis techniques to extract the properties of the observed waves in both magnetohydrodynamic (MHD) and kinetic scales. At the MHD scale, outward-propagating Alfvén waves dominate both intervals, and outward-propagating fast magnetosonic waves present the second-largest contribution in the spectral energy density. At kinetic scales, we identify the circularly polarized plasma waves propagating near the proton gyrofrequency in both intervals. However, the sense of magnetic polarization in the spacecraft frame is observed to be opposite in the two intervals, although they both possess a sunward background magnetic field. The ion-scale plasma wave observed in the first interval can be either an inward-propagating ion cyclotron wave (ICW) or an outward-propagating fast-mode/whistler wave in the plasma frame, while in the second interval it can be explained as an outward ICW or inward fast-mode/whistler wave. The identification of the exact kinetic wave mode is more difficult to confirm owing to the limited plasma data resolution. The presence of ion-scale waves near the Sun suggests that ion cyclotron resonance may be one of the ubiquitous kinetic physical processes associated with small-scale magnetic fluctuations and kinetic instabilities in the inner heliosphere.

Analysis, design and fabrication of reconfigurable patch antenna on magnetodielectric composite substrate with biased ferrite particles

This study proposes a circular microstrip patch antenna on a magnetodielectric composite consisting of ferrite particles dispersed in a polymer matrix. The antenna operation is theoretically analysed using the cavity model and it is demonstrated that under the application of an external magnetic field it exhibits two resonant frequencies with opposite polarization sense. The theoretical analysis is verified numerically using a commercial electromagnetic (EM) simulator software. Moreover, it is shown that the antenna operating frequencies and polarization can be controlled through the variations of the applied magnetic field. An antenna prototype is fabricated in our laboratory and satisfactory agreement is observed between numerical and measurement results. The proposed antenna model is suitable for reconfigurable antenna applications at the 5 GHz frequency band.

Switchable T-Slot for Dual-Circularly-Polarized Slot-Array Antennas in Ka-Band

This letter presents two slotted array antennas working in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band with switchable circular polarization capability. The first prototype is a series-fed slotted-waveguide linear array composed of ten T-shaped slots. The second antenna is a 2-D array with 2 × 2 T-shaped slots fed by a corporate distribution network. In both cases, a reflection coefficient below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 10 dB has been experimentally observed within the targeted frequency band between 29.5 and 30.5 GHz. Good polarization purity is achieved for both polarization senses and in both prototypes. The fundamental contribution of this letter is to propose a simple mechanism to switch the circular polarization sense in a low-cost, low-profile, and high-efficient antenna. The design and experimental results confirm that the solution is suitable for both one- and two-dimensional arrays in the millimeter-wave band.

Polarization-Agile Circular Polarized Antenna Based on Proximity Feeding Technique

In this letter, the design and experimental validation of polarization-agile circular polarized antenna are presented. The antenna is comprised of a patch antenna with truncated slits and two proximity feedlines. The antenna produces a vertical linear polarized wave when it is fed by a proximity feedline. Horizontal linear polarized wave is then generated by applying a potential difference between two proximity feedlines. The quadrature phase difference between two orthogonal polarized waves is created by adding truncated slits into the patch antenna. By swapping the polarity of the proximity feedlines, polarization sense can be changed. The distributed circuit model is presented to describe the working mechanism of the antenna. Patch antenna with circular polarization agility is then validated through passive-type and active-type switching circuits. The measured axial ratio bandwidth is 4.085% (100 MHz), and the fractional impedance bandwidth is greater than 7% for the left-handed and right-handed circular polarized radiations.

Circularly polarized rectangular dielectric resonator antenna with elliptical aperture feed for 5 GHz ISM band

In this article, a new elliptical slot aperture feed circularly polarized (CP) rectangular dielectric resonator antenna (RDRA) has been proposed. The nonresonant slot excites two spatially orthogonal resonant frequencies in RDRA to produce CP waves. TEx111 and TEy111 are the orthogonal modes produced by the 450 inclined elliptical slot with respect to microstrip feed. Also, the sense of polarization at the resonance frequencies can be controlled by changing the orientation of the slot. The antenna performances in terms of impedance bandwidth, 3-dB axial ratio, and gain are validated experimentally. The proposed antenna can be used in 5 GHz ISM band for WiFi/satellite communications.

A compact uni-planar printed slot UWB antenna with reconfigurable functionality

In this article, a compact uni-planar printed slot antenna with SAS geometry is proposed, facilitating UWB multi-bands, band-rejectionality, LP and CP using reconfigurable technique, with 2 x SMD diodes. For SMD1-ON, SMD2-ON, states antenna operates in SAS mode from 2.4–10.6 GHz and for SMD1-OFF, SMD2-OFF states antenna operates in slot mode, resulted in band-rejection from 2.7–4.3 GHz. For aforementioned states LP patterns are observed. At [(SMD1-OFF, SMD2-ON) and (SMD1-ON, SMD2-OFF)] states, the antenna asserts CP with minimum 3-dB axial ratio at 6.05 GHz and 9.31 GHz, respectively, where the polarization sense is electronically reversed asserting dual-sense CP . Additionally, it shows band-rejection from 2.5–5 GHz for (SMD1-OFF, SMD2-ON) state and 3.6–4.8 GHz for (SMD1-ON, SMD2-OFF) state. A prototype antenna of size is fabricated and measured to be potentially used in cognitive radio systems and UWB applications.