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L-band spaceborne polarimetric synthetic aperture radar (PolSAR) data has been well used for the high-resolution retrieval of the ionospheric Faraday rotation (FR). A vast majority of these retrievals were, however, conducted on PolSAR data of lands, with only a very few over oceans. For the global imaging of the Earth's ionosphere, the retrieval of oceanic ionosphere is indispensable. This paper aims to furnish a deep insight into the FR retrieval on oceans using the widely used Bickel-Bates estimator based on the two cross-circular polarizations ${Z_{12}}$ Z 12 and ${Z_{21}}$ Z 21 . The FR estimates (FRE) on oceans are evaluated in detail by comparing with those on lands on four ALOS PALSAR datasets. The achieved oceanic FRE are shown to possess comparable or even better quality than those on lands. It occurs in three of the four scenes that the selected ocean sub-area holds a smaller standard deviation (STD) of FRE (less than 0.7000°) than all the selected land sub-areas. Especially, the quality of FRE is shown to be closely linked to the dispersed degree of the magnitude of the conjugate product of ${Z_{12}}$ Z 12 and ${Z_{21}}$ Z 21 via the analysis of coefficient of variation (CV), according to which the unusual occurrence of larger magnitude level corresponding to larger STD of FRE can be explained. Nevertheless, compared with CV, the magnitude of the polarimetric coherence between ${Z_{12}}$ Z 12 and ${Z_{21}}$ Z 21 (i.e. $\left| \gamma \right|$ γ ) is identified as a better index to measure the quality of FRE. A smaller STD of FRE appears along with a larger $\left| \gamma \right|$ γ . Three of the four scenes show that the selected ocean sub-area bears a larger mean of $\left| \gamma \right|$ γ (greater than 0.9890) in comparison with all the selected land sub-areas. This work can promote the ionospheric research over oceans and to the correction of ionospheric effects in oceanic L-band spaceborne polarimetric radar data as well. [ABSTRACT FROM AUTHOR]

There is increasing interest in space domain awareness worldwide, motivating investigation of the use of non-traditional sensors for space surveillance. One such class of sensor is VHF wind profiling radars, which have a low cost relative to other radars typically applied to this task. These radars are ubiquitous throughout the world and may potentially offer complementary space surveillance capabilities to the Space Surveillance Network. This paper updates an initial investigation on the use of Buckland Park VHF wind profiling radars for observing resident space objects in low Earth orbit to further investigate the space surveillance capabilities of the sensor class. The radar was operated during the Australian Defence "SpaceFest" 2019 activity, incorporating new beam scheduling and signal processing functionality that extend upon the capabilities described in the initial investigation. The beam scheduling capability used two-line element propagations to determine the appropriate beam direction to use to observe transiting satellites. The signal processing capabilities used a technique based on the Keystone transform to correct for range migration, allowing the development of new signal processing modes that allow the coherent integration time to be increased to improve the SNR of the observed targets, thereby increasing the detection rate. The results reveal that 5874 objects were detected over 10 days, with 2202 unique objects detected, representing a three-fold increase in detection rate over previous single-beam direction observations. The maximum detection height was 2975.4 km, indicating a capability to detect objects in medium Earth orbit. A minimum detectable RCS at 1000 km of −10.97 dBm2 (0.09 m2) was observed. The effects of Faraday rotation resulting from the use of linearly polarised antennae are demonstrated. The radar's utility for providing total electron content (TEC) measurements is investigated using a high-range resolution mode and high-precision ephemeris data. The short-term Fourier transform is applied to demonstrate the radar's ability to investigate satellite rotation characteristics and monitor ionospheric plasma waves and instabilities. [ABSTRACT FROM AUTHOR]

An X-pinch load driven by an intense current pulse (> 100 kA in ∼100 ns) can result in the formation of a small radius, runaway compressional micro-pinch. A micro-pinch is characterized by a hot (>1 keV), current-driven (> 100 kA), high-density plasma column (near solid density) with a small neck diameter (1–10 µm), a short axial extent (< 1 mm), and a short duration (≲1 ns). With material pressures often well into the multi-Mbar regime, a micro-pinch plasma often radiates an intense, sub-ns burst of sub-keV to multi-keV x rays. A low-density coronal plasma immediately surrounding the dense plasma neck could potentially shunt current away from the neck and thus reduce the magnetic drive pressure applied to the neck. To study the current distribution in the coronal plasma, a Faraday rotation imaging diagnostic (1064 nm) capable of producing simultaneous high-magnification polarimetric and interferometric images has been developed for the MAIZE facility at the University of Michigan. Designed with a variable magnification (1–10×), this diagnostic achieves a spatial resolution of ∼35 µm, which is useful for resolving the ∼100-μm-scale coronal plasma immediately surrounding the dense core. This system has now been used on a reduced-output MAIZE (100–200 kA, 150 ns) to assess the radial distribution of drive current immediately surrounding the dense micro-pinch neck. The total current enclosed was found to increase as a function of radius, r, from a value of ≈ 50 ± 25 kA at r ≈ 140 µm (at the edge of the dense neck) to a maximal value of ≈ 150 ± 75 kA for r ≥ 225 µm. This corresponds to a peak magnetic drive pressure of ≈ 75 ± 50 kbar at r ≈ 225 µm. The limitations of these measurements are discussed in the paper. [ABSTRACT FROM AUTHOR]

Faraday rotation measure (RM) is arguably the most practical observational tracer of magnetic fields in the diffuse circumgalactic medium (CGM). We sample synthetic Faraday rotation skies of Milky Way-like galaxies in TNG50 of the IllustrisTNG project by placing an observer inside the galaxies at a solar circle-like position. Our synthetic RM grids emulate specifications of current and upcoming surveys; the NRAO VLA Sky Survey (NVSS), the Polarisation Sky Survey of the Universe's Magnetism (POSSUM), and a future Square Kilometre Array (SKA1-mid) polarization survey. It has been suggested that magnetic fields regulate the survival of high-velocity clouds. However, there is only a small number of observational detections of magnetized clouds thus far. In the first part of the paper, we test conditions for the detection of magnetized circumgalactic clouds. Based on the synthetic RM samplings of clouds in the simulations, we predict upcoming polarimetric surveys will open opportunities for the detection of even low-mass and distant clouds. In the second part of the paper, we investigate the imprint of the CGM in the all-sky RM distribution. We test whether the RM variation produced by the CGM is correlated with global galaxy properties, such as distance to a satellite, specific star formation rate, neutral hydrogen covering fraction, and accretion rate to the supermassive black hole. We argue that the observed fluctuation in the RM measurements on scales less than 1○, which has been considered an indication of intergalactic magnetic fields, might in fact incorporate a significant contribution of the Milky Way CGM. [ABSTRACT FROM AUTHOR]

The MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) is one of the MeerKAT large survey projects, designed to pathfind SKA key science. MIGHTEE is undertaking deep radio imaging of four well-observed fields (COSMOS, XMM -LSS, ELAIS S1, and CDFS) totaling 20 square degrees to μJy sensitivities. Broad-band imaging observations between 880 and1690 MHz yield total intensity continuum, spectro-polarimetry, and atomic hydrogen spectral imaging. Early science data from MIGHTEE are being released from initial observations of COSMOS and XMM –LSS. This paper describes the spectro-polarimetric observations, the polarization data processing of the MIGHTEE early science fields, and presents polarization data images and catalogues. The catalogues include radio spectral index, redshift information, and Faraday rotation measure synthesis results for 13 267 total intensity radio sources down to a polarized intensity detection limit of ∼20 μJy bm−1. Polarized signals were detected from 324 sources. For the polarized detections, we include a catalogue of Faraday Depth from both Faraday Synthesis and Q, U fitting, as well as total intensity and polarization spectral indices. The distribution of redshift of the total radio sources and detected polarized sources are the same, with median redshifts of 0.86 and 0.82, respectively. Depolarization of the emission at longer-wavelengths is seen to increase with decreasing total-intensity spectral index, implying that depolarization is intrinsic to the radio sources. No evidence is seen for a redshift dependence of the variance of Faraday depth. [ABSTRACT FROM AUTHOR]

Here, we consider the general radiative transfer theory in a magnetized atmosphere for any value of parameter |$x=\omega _B/\omega \simeq 0.933\times 10^{-8}\lambda (\mu \mathrm{m}) B(\text{G})$|⁠ , where ω B is the cyclotron frequency of electron rotation and ω is the angular frequency of considered monochromatic radiation. The main term of the radiative transfer equations  |$\textbf {J}_{\alpha \beta }$| for the Stokes parameters I, V, U , and Q describes the scattering of radiation coming from all directions and distances. All Stokes parameters of the incident radiation mutually transform into each other along their path due to interference and different cross-sections for them. To find this transformation of the Stokes parameters one has to solve the complex system of transfer equations without the sources and term |$\textbf {J}_{\alpha \beta }$|⁠. This is done in our paper. First, we present the general solution and then give the solution for the case of a homogeneous magnetic field, where the formulas have clear algebraic form. We note that for small parameter x our formulas describe the known Faraday rotation. Our formulas allow us to derive an integral equation for the density of polarized radiation, multiple scattered in a magnetized atmosphere for any values of the parameter x. The obtained correct radiation transfer equation allows us to calculate the Stokes parameters of radiation emerging from an atmosphere, in particular, for the Milne problem. [ABSTRACT FROM AUTHOR]

This paper presents a novel scheme to online measure the birefringence of the sensing fiber in all‐fiber optic current transformer (AFOCT) system, which monitors the current on direct current (DC) transmission lines using the Faraday magneto‐optic effect in sensing fibers. In this scheme, by purposefully varying the difference of square‐wave modulated phases via the phase modulator in the AFOCT system, different system transmittances can be obtained. On the basis of the relationship between the system transmittance and linear and circular birefringences, an online measurement scheme of both the linear and circular birefringences of the sensing fibers can be established. In this scheme, the AFOCT system is described by the transmission model based on the Jones matrices, with which the current on DC transmission lines can be measured from the phase shift caused by the Faraday effect. Then, under different square‐wave modulated phases, the system transmittance models are constructed with respect to the linear and circular birefringences of the sensing fiber. For a given sensing fiber with certain linear and circular birefringences, the specific system transmittances are determined and are the curves in space in the respective system transmittance models. Subsequently, these curves in space can be projected onto the coordinate plane composed of the linear and circular birefringence coordinate axes, where the intersection point of the projected plane curves gives the to‐be‐measured values of the linear and circular birefringences of the sensing fiber. The proposed scheme is validated by the preset linear and circular birefringences of the sensing fiber, with different linear birefringences of the polarization‐maintaining fiber. The measurement results show the values consistent with the preset ones. [ABSTRACT FROM AUTHOR]

Radio waves propagating the ionosphere are subject to a number of unpredictable and corrupting effects, the most significant of which are phase path reduction, Faraday rotation, and scintillation. A method of measuring these effects is necessary in order to study and understand the solar-terrestrial connections, as well as to anticipate their impact on radio systems. However, limitations in current measurement solutions, most notably the lack of direct ionospheric Faraday rotation measurement capability, restricts the ability to characterize the ionosphere to a sufficient degree for applications such as the detection of coronal mass ejections. The rise in popularity of small satellites presents a new cost-effective opportunity to study and observe the ionosphere in detail, however the challenge of realizing a beacon within the constraints of a small satellite system must be overcome. In this paper, we introduce a measurement technique that builds on past multi-frequency beacons, incorporating the well established differential phase technique, as well as introducing a new differential polarization technique. We achieve this by employing linearly polarized beacon signals, which enables us to separate phase path reduction and Faraday rotation into a phase and polarization error respectively. The introduction of linear polarization overcomes a key limitations in current ionospheric measurement techniques: eliminating errors associated with indirect Faraday rotation measurement. The additional polarization data also enables absolute unambiguous measurement of both parameters with fewer and lower frequencies than conventional solutions, as well as without the need for precise satellite clock, phase biases and positioning data. These characteristics correspond with a reduction in the size, power and complexity of the satellite payload, and as a result, our technique better suited to small satellite applications. To validate the capability of measuring the ionosphere within the constraints of a small satellite package, we establish the influence of system noise, weak scattering, clock errors and antenna characteristics on the measurement technique. We then use this to inform a starting point for a CubeSat beacon and receiver design solution which achieves unambiguous and high-resolution measurement of ionospheric parameters with practicable system requirements and constraints. This starting point demonstrates that a resolution of 12 mTECU and 0.03 rad/m2 for the electron density and Faraday rotation estimates respectively, as well as useful scintillation measurements dominated by scintillation noise may be achieved utilizing a tri-band 3U CubeSat beacon with frequencies 144.2 MHz, 432.6 MHz, and 1297.8 MHz, a transmitter power of no more than 4 watts, and antenna requirements consistent with a dipole type antenna. [ABSTRACT FROM AUTHOR]

Recently, some fast radio bursts (FRBs) have been reported to exhibit complex and diverse variations in Faraday rotation measurements (RM) and polarization, suggesting that dynamically evolving magnetization environments may surround them. In this paper, we investigate the Faraday conversion (FC) effect in a binary system involving an FRB source and analyze the polarization evolution of FRBs. For a strongly magnetized high-mass companion binary, when an FRB with ∼100% linear polarization passes through the radial magnetic field of the companion star, the circular polarization (CP) component will be induced and oscillate symmetrically around the point with the degree of CP equal to zero, the rate and amplitude of the oscillation decrease as the frequency increases. The very strong plasma column density in the HMCBs can cause CP to oscillate with frequency at a very drastic rate, which may lead to depolarization. Near the superior conjunction of the binary orbit, the DM varies significantly due to the dense plasma near the companion, and the significant FC also occurs in this region. As the pulsar moves away from the superior conjunction, the CP gradually tends toward zero and then returns to its value before incidence. We also investigate the effect of the rotation of the companion star. We find that a sufficiently significant RM reversal can be produced at large magnetic inclinations and the RM variation is very diverse. Finally, we apply this model to explain some polarization observations of PSR B1744-24A and FRB 20201124A. [ABSTRACT FROM AUTHOR]

The L-band geosynchronous synthetic aperture radar (GEO-SAR) has been widely praised for its advantages of short revisit time, wide coverage and stable backscattering information acquisition. However, due to the ultra-long integrated time, the echo will be affected by the time-variant background ionosphere, leading in particular to defocusing in the azimuth direction. Existing compensation methods suitable for low Earth orbit SAR (LEO-SAR) are based on the SAR image or the semi-focused image at the ionospheric phase screen, assuming that the ionosphere is time-frozen for a short integrated period; thus, accurate reconstruction of the time-variant characteristics for the ionosphere in GEO-SAR cannot be achieved. In this paper, a compensation method of background ionospheric effects on L-band GEO-SAR with fully polarimetric data is proposed. Considering the continuous variation of the ionosphere within the synthetic aperture, a decompression processing is proposed to reconstruct the echo by recovering the temporal sampling according to the imaging geometry. By virtue of the Faraday rotation angle, the time-variant total electron content (TEC) is accurately estimated with the reconstructed echo. Based on the established error model, the ionospheric effects are well compensated with the estimated TEC. Simulations with the real SAR data from ALOS-2 and the measured time-variant TEC from USTEC validate the effectiveness and performance of the proposed method. The impacts from thermal noise and polarimetric calibration error are also quantitatively analyzed. From this, the error thresholds are given to guarantee compensation accuracy, namely 18.96 dB for SNR, −15.63 dB for crosstalk and −1.02 dB to 0.31 dB for the amplitude of the channel imbalance, and the argument of the channel imbalance is suggested to be maintained as close to zero as possible. [ABSTRACT FROM AUTHOR]

Iron garnet is a material with a good Faraday effect, especially in the visible and infrared wavelengths, and it has been found that the magneto-optical effect of this material can be enhanced by the introduction of Bi3+ ions. In this work, the effect of the gyration vector in the dielectric constant on the refractive index is investigated by fitting the equation of the gyration vector in the dielectric constant of BixY3-xFe5O12 based on that the gyration vector of iron garnet films is proportional to the magnetization intensity. After comparing the gyration vector formulation of BixY3-xFe5O12, the Faraday effect and transmittance of the film with a thickness of 200 nm were calculated numerically, and the results showed that Bi3Fe5O12 has a better strengthening effect than Y3Fe5O12. The authors analyzed the Faraday rotation angle and transmittance with different thicknesses of Bi3Fe5O12 and also investigated the effect of the applied magnetic field on the Faraday rotation angle, reaching -58° at a magnetic field of 1.5 T. Compared with the model with surface metal structure, the magneto-optical film studied in this paper has the advantages of easy preparation and large Faraday rotation angle, and provides a new idea for the development of magneto-optical devices. [ABSTRACT FROM AUTHOR]

A Weyl semimetal can be considered as a system composed of two Weyl cones breaking time-reversal symmetry, which exhibits strong anisotropic hyperbolic characteristics. The off diagonal components of the permittivity tensor of a Weyl semimetal produce the Faraday and Kerr effects. In this paper, we investigate the Goos–Hänchen (GH) shifts when a light is reflected from the interface of air and a Weyl semimetal. It is demonstrated that the angular GH shift is still tiny; however, the spatial GH shift can be huge and is very sensitive to change in the incident angle. The spatial GH shift can change from positive to negative with an increase in the incident angle. The spatial GH shifts vary at different distances of two Weyl cones and thicknesses of a Weyl semimetal film. Furthermore, the tunable GH shift can be realized by changing the tilting parameter and Fermi energy. These adjustable and giant GH shifts may find practical applications in optical shift devices and optical sensors. [ABSTRACT FROM AUTHOR]

Spectroscopic measurements of the low solar corona are crucial to understanding the mechanisms that heat the corona and accelerate the solar wind, yet the lowest solar radii ( R ⊙ ) of the corona are difficult to observe. Our expedition collected narrow wavelengths of visible light at 530.3, 637.4, and 789.2 nm emitted by Fe xiv, x, and xi ions, respectively, from the total solar eclipse on 2019 July 2 at 20:40 UTC in Rodeo, Argentina with a bespoke 3-channel spectrometer. This paper describes the instrument and data calibration method that enables diagnostics out to ≈ 1.0 R ⊙ above the solar limb within a bright helmet streamer. We find that Fe x and xi lines are dominant through 0.3 R ⊙ , with Fe xiv maintaining a stronger signal at higher elevations. Thermal line width broadening is consistent with 1.5 MK for the cooler Fe x, 2 MK for Fe xi, and 3 MK for the hotter Fe xiv line, which can be interpreted as differing density scale heights within isolated, isothermal flux tubes. The Doppler measurements correspond to bulk plasma motion ranging from −12 to +2.5 km s−1, with Fe xiv moving at nearly an assumed solid body rotation rate throughout 1.0 R ⊙ . After considering coronal rotation, these measurements are likely associated with plasma motion along the dominant longitudinal orientation of the magnetic field at the streamer base within 0.4 R ⊙ . These results show that high-resolution spectroscopy of visible light offers valuable diagnostics of the low corona, and lend insight into the interconnected loop complexity within helmet streamers. [ABSTRACT FROM AUTHOR]

The application of a bidirectional laser requires the laser intensity in both directions to be balanced. However, the CW and CCW light intensities in current bidirectional erbium-doped fiber laser experiments differ due to the gain competition effect. There is no report on equalizing the intensity in the CW and CCW directions. This paper proposes a bidirectional non-reciprocal optical attenuator using the Faraday optical rotation effect. Continuous attenuation adjustment is realized by changing the angle between the polarizer's transmission axis and the linear polarized light. In this study, we analyzed the influence of different parameters on the device's performance, built a non-reciprocal attenuator, and tested the bidirectional attenuation curve, which was consistent with the simulation results. The device was integrated into a bidirectional fiber laser, and the light intensity in both directions was balanced through non-reciprocal adjustment. Combined with closed-loop control, the average intensity difference fluctuation between the two directions was controlled at 0.28% relative to the average power, realizing stable long-term bidirectional fiber laser intensity equalization. [ABSTRACT FROM AUTHOR]

This paper proposes and examines a finite element method (FEM) for a Maxwell obstacle problem in electric shielding. The model is given by a coupled system comprising the Faraday equation and an evolutionary variational inequality (VI) of Ampère-Maxwell-type. Based on the leapfrog (Yee) time-stepping and the Nédélec edge elements, we set up a fully discrete FEM where the obstacle is discretized in such a way that no additional nonlinear solver is required for the computation of the discrete VI. While the L²-stability is achieved for the discrete solutions and the associated difference quotients, the scheme only guarantees the L¹-stability for the discrete magnetic curl field in the obstacle region. The lack of the global L²-stability for the magnetic curl field is justified by the low regularity issue in Maxwell obstacle problems and turns to be the main challenge in the convergence analysis. Our convergence proof consists of two main stages. First, exploiting the L¹-stability in the obstacle region, we derive a convergence result towards a weaker system involving smooth feasible test functions. In the second step, we recover the original system by enlarging the feasible test function set through a specific constraint preserving mollification process in the spirit of Ern and Guermond [Comput. Methods Appl. Math., 16 (2016), pp. 51-75]. This paper is closed by three-dimensional numerical results of the proposed FEM confirming the theoretical convergence result and, in particular, the Faraday shielding effect. [ABSTRACT FROM AUTHOR]

This paper proposes the phenomenon of extraordinary optical transmission via a magneto-plasmonic nanostructure, which combines magnetic and plasmonic functionalities. The structure includes an active magnetic film magnetized perpendicular to its surface and a plasmonic metal film, perforated with subwavelength circular annular arrays, with a ring placed in the middle of each annular circle. We use the finite element method and the finite-difference time-domain method for simulation of the structure. Numerical analysis shows an improvement in the Faraday rotation and optical transmission, simultaneously, in a magneto-plasmonic structure based on a silver- and bismuth-substituted ferrite garnet. Simultaneous improvement is achieved by coupling the TE and TM waveguide-plasmon modes. The amount of enhancement is adjusted by changing the dimensions, the periodicity of the hole arrays, and the refractive index of the materials filled in the holes. The influence of excitation of the two kinds of plasmon modes and the application of the external magnetic field are used to enhance the optical response. The resulting investigation shows two resonance peaks in the near-infrared range of the Faraday effect spectrum. Because of the strong Faraday rotation coinciding with the dual-band transmission of approximately 90%, the maximum figure of merit can also be obtained. Finally, this structure is investigated as a sensor in different reflective indexes from 1 to 1.5 RIU, and sensitivity of 45.97 nm/RIU was achieved. The potential applications of these nanostructures include, for example, subwavelength optics, optoelectronic devices, biosensing devices, and magneto-optical devices. [ABSTRACT FROM AUTHOR]

Cavity ring-down spectroscopy (CRDS) is a well-established, highly sensitive absorption technique whose sensitivity and selectivity for trace radical sensing can be further enhanced by measuring the polarization rotation of the intracavity light by the paramagnetic samples in the presence of a magnetic field. In this paper, we highlight the use of this Faraday rotation cavity ring-down spectroscopy (FR-CRDS) for the detection of HO2 radicals. In particular, we use a cold atmospheric pressure plasma jet as a highly efficient source of HO2 radicals and show that FR-CRDS in the near-infrared spectral region (1506 nm) has the potential to be a useful tool for studying radical chemistry. By simultaneously measuring ring-down times of orthogonal linearly polarized light, measurements of Faraday effect-induced rotation angles (θ) and absorption coefficients (α) are retrieved from the same data set. The Faraday rotation measurement exhibits better long-term stability and enhanced sensitivity due to its differential nature, whereby highly correlated noise between the two channels and slow drifts cancel out. The bandwidth-normalized sensitivities are α m i n = 2.2 × 1 0 − 11 cm − 1 Hz − 1 / 2 and θ m i n = 0.62 nrad Hz − 1 / 2 . The latter corresponds to a minimum detectable (circular) birefringence of Δ n m i n = 5 × 1 0 − 16 Hz − 1 / 2 . Using the overlapping qQ3(N = 4–9) transitions of HO2, we estimate limits of detection of 3.1 × 108 cm−3 based on traditional (absorption) CRDS methods and 6.7 × 107 cm−3 using FR-CRDS detection, where each point of the spectrum was acquired during 2 s. In addition, Verdet constants for pertinent carrier (He, Ar) and bulk (N2, O2) gases were recorded in this spectral region for the first time. These show good agreement with recent measurements of air and values extrapolated from reported Verdet constants at shorter wavelengths, demonstrating the potential of FR-CRDS for measurements of very weak Faraday effects and providing a quantitative validation to the computed rotation angles. [ABSTRACT FROM AUTHOR]

Polarization calibration of interferometric observations is a costly procedure and in some cases (e.g., due to limited coverage of parallactic angle for the calibrator), it may not be possible to carry out this process. To avoid this worst-case scenario, while extending the possibilities for the exploitation of polarization interferometric observations, the use of a new set of calibration-independent quantities (closure traces) has been proposed. However, these quantities suffer from some degeneracies, so their use in practical situations may be rather limited. In this paper, we explore the use of closure traces on simulated and real observations, showing that (with the proper selection of fitting parameters) it is possible to retrieve information on the source polarization using only closure traces and to constrain spatially resolved polarization. We carried out the first application of closure traces to the brightness modeling of real data, using the ALMA observations of M87 conducted during the April 2017 EHT campaign and quantifying a gradient in the Faraday rotation along the source structure (the M87 jet). This work opens the possibility to apply similar strategies to observations from any kind of interferometer (with a special focus on VLBI), whereby quantities such as the differential rotation measure or the spatially resolved polarization can be retrieved. [ABSTRACT FROM AUTHOR]

Spontaneous and external magnetic fields interacting with plasmas are essential in high-energy-density and magnetic confinement fusion physics. Measuring these magnetic fields, especially their topologies, is crucial. This paper develops a new type of optical polarimeter based on the Martin–Puplett interferometer (MPI), which can probe magnetic fields with the Faraday rotation method. We introduce the design and working principle of an MPI polarimeter. With the laboratory tests, we demonstrate the measurement process and compare the results with the measurement result of a Gauss meter. These very close results verify the polarization detection capability of the MPI polarimeter and show the potential for its application in magnetic field measurement. [ABSTRACT FROM AUTHOR]

The reconstruction of Faraday depth structure from incomplete spectral polarization radio measurements using the RM synthesis technique is an underconstrained problem requiring additional regularization. In this paper, we present cs-romer : a novel object-oriented compressed sensing framework to reconstruct Faraday depth signals from spectropolarization radio data. Unlike previous compressed sensing applications, this framework is designed to work directly with data that are irregularly sampled in wavelength-squared space and to incorporate multiple forms of compressed sensing regularization. We demonstrate the framework using simulated data for the VLA telescope under a variety of observing conditions, and we introduce a methodology for identifying the optimal basis function for reconstruction of these data, using an approach that can also be applied to data sets from other telescopes and over different frequency ranges. In this work, we show that the delta basis function provides optimal reconstruction for VLA L -band data and we use this basis with observations of the low-mass galaxy cluster Abell 1314 in order to reconstruct the Faraday depth of its constituent cluster galaxies. We use the cs-romer framework to de-rotate the Galactic Faraday depth contribution directly from the wavelength-squared data and to handle the spectral behaviour of different radio sources in a direction-dependent manner. The results of this analysis show that individual galaxies within Abell 1314 deviate from the behaviour expected for a Faraday-thin screen such as the intra-cluster medium and instead suggest that the Faraday rotation exhibited by these galaxies is dominated by their local environments. [ABSTRACT FROM AUTHOR]

More than 100 rotating radio transients (RRATs) have been discovered since 2006. However, it is unclear whether RRATs radiate in nulling states. PSR J0628+0909 has been classified as an RRAT. In this paper, we study the single pulses and integrated pulse profile of PSR J0628+0909 to check whether we can detect pulsed radio emission in the nulling states. We also aim to study the polarization of the RRAT and its relationship to the general pulsar population. We used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to observe PSR J0628+0909 in the frequency range from 1.0 to 1.5 GHz. We searched for strong single pulses and looked for pulsed emission in the RRAT nulling states. Polarization profiles, the single-pulse energy distribution, and waiting-time statistics were measured. The Faraday rotation measure and dispersion measure values are updated with the current observation. The single-pulse polarization behaviours show great diversity, similar to the case of pulsars. Based on the integrated pulse profile and single-pulse energy statistics, we argue that continuous pulsar-like emission exists in addition to the transient-like burst emission for PSR J0628+0909. We find that the pulse waiting time is not correlated with the pulse energy and conclude that the strong transient emission of RRAT is not generated by the energy store–release mechanism. [ABSTRACT FROM AUTHOR]

The spaceborne P-band fully polarimetric synthetic aperture radar (SAR) working system is highly susceptible to the scintillation effects induced by ionospheric irregularities due to its low carrier frequency. The scintillation phase error (SPE) is a dominant factor that leads to azimuth decorrelation. The aperture-dependent and spatial-varying characteristics of the SPE promote the complexity of the SPE estimation and compensation. In this paper, a methodology is described that compensates the SPE by estimating the Faraday rotation (FR) angle from fully polarimetric SAR data. The multi-aperture scheme is adopted, including the sub-aperture FR estimation, multi-aperture splicing, and overall compensation, to take the complicated characteristics of the aperture-dependent and spatial-varying SPE into account. The methodology is finally validated on simulated data derived from the airborne P-band SAR real data, and compared with an existing method. The new method does not need prior knowledge of the ionospheric height. Furthermore, its performance is investigated in relation to several key factors in different simulation conditions. [ABSTRACT FROM AUTHOR]

With the development of optical communication technology and photonic integrated circuits, non-reciprocal devices have been widely studied and applied as an important part of optical communication systems. Magneto-optical isolators and circulators based on magneto-optical effect are currently the most widely used non-reciprocal devices. In order to integrate nonreciprocal devices into silicon wafers, magneto-optical thin films with comparable performance to bulk magneto-optical materials need to be prepared. In the near-infrared band (1 550 nm), rare earth iron garnet (RIG) represented by yttrium iron garnets (Y3Fe5O12, YIG) has excellent magneto-optical effects and become one of the most promising magneto-optical materials. It is found that doping with rare earth ions can effectively improve the magneto-optical properties of YIG thin films, especially Bi3+ and Ce3+ doped YIG exhibit giant Faraday effect. In this paper, the Faraday effect principle is briefly introduced, three common growth methods of RIG magneto-optical thin films and their research progress in recent years are reviewed, and the application of RIG magneto-optical thin films in optical isolators and circulators are summarized. Finally, the future development trend of magneto-optical films is prospected. [ABSTRACT FROM AUTHOR]

The practice of harvesting vibration energy from machine tools, windmill blades, etc., and converting it into electric energy to power low-power electronic circuits has attracted wide attention from experts and scholars. Abundant vibrations that exist in the moving vehicle can be harvested to power sensors in tire pressure monitoring. In this paper, for the first time, a device is proposed to harvest the rotational vibration energy with the iron–gallium alloy (magnetostrictive material) as the core material. Such a device utilizes the coupling characteristics of Villarreal effect and Faraday electromagnetic effect to convert the vibration energy generated by the moving vehicle into electric energy. Upon completion of the design of the magnetostrictive rotational vibration energy harvester, the influence law of key factors, including substrate material, substrate size, and pre-magnetization field arrangement on the harvesting capability of the device, was studied in detail through experiments. An electric motor and vibration exciter were used to apply varied excitation forms to the harvester, and the output patterns of the harvester under conditions of wheel rotation, road bumps, and random vibration were fully analyzed. In addition, the correlation between the deformation of the cantilever beam and harvester performance was also investigated. The results have shown that at the acceleration of 9.6 g and the rotational speed of 90 r/min, the harvester can reach the output voltage of 1.22 V. Consequently, it demonstrates the feasibility of employing the magnetostrictive harvester to gather rotational vibration energy and provides theoretical guidance for further and deeper research on the harvester. [ABSTRACT FROM AUTHOR]

The measurement of MOKE (Magneto-Optical Kerr Effect) magnetization loops in a wide-field Kerr microscope offers the advantage that the relevant domain images along the loop can be readily recorded. As the microscope’s objective lens is exposed to the magnetic field, the loops are usually strongly distorted by non-linear Faraday rotations of the polarized light that occur in the objective lens and that are superimposed to the MOKE signal. In this paper, an experimental method, based on a motorized analyzer, is introduced which allows to compensate the Faraday contributions, thus leading to pure MOKE loops. A wide field Kerr microscope, equipped with this technology, works well as a laser-based MOKE magnetometer, additionally offering domain images and thus providing the basis for loop interpretation. [ABSTRACT FROM AUTHOR]

Generation of spontaneous magnetic fields (SMFs) is one of the most interesting phenomena accompanying an intense laser–matter interaction. One method of credible SMFs measurements is based on the magneto-optical Faraday effect, which requires simultaneous measurements of an angle of polarization plane rotation of a probe wave and plasma electron density. In classical polaro-interferometry, these values are provided independently by polarimetric and interferometric images. Complex interferometry is an innovative approach in SMF measurement, obtaining information on SMF directly from a phase–amplitude analysis of an image called a complex interferogram. Although the theoretical basis of complex interferometry has been well known for many years, this approach has not been effectively employed in laser plasma research until recently; this approach has been successfully implemented in SMF measurement at the Prague Asterix Laser System (PALS). In this paper, proprietary construction solutions of polaro-interferometers are presented; they allow us to register high-quality complex interferograms in practical experiments, which undergo quantitative analysis (with an original software) to obtain information on the electron density and SMFs distributions in an examined plasma. The theoretical foundations of polaro-interferometric measurement, in particular, complex-interferometry, are presented. The main part of the paper details the methodology of the amplitude–phase analysis of complex interferograms. This includes software testing and examples of the electron density and SMF distribution of a laser ablative plasma generated by irradiating Cu thick planar targets with an iodine PALS laser at an intensity above about 1016 W/cm2. [ABSTRACT FROM AUTHOR]

Dispersion interferometry (DI) is being employed on an increasing number of fusion experiments to measure the plasma density with a minimal sensitivity to vibrations. DIs employed in high-density experiments use phase modulation techniques up to several hundred kilohertz to enable quadrature detection and to be unaffected by variations of the signal amplitude. However, the evaluation of the temporal interferogram can be a significant source for phase errors and does not have an established processing method. There are two non-approximation-based methods currently in use: one using the ratio of amplitudes in the signal's Fourier spectrum and the other using its sectioned integration. Previously, the methods could not be used simultaneously since they differ in their respective calibration point. In this paper, we present a technique to use both phase evaluation methods simultaneously using quadrature correction methods. A comparison of their strengths and weaknesses is presented based on identical measurements indicating one to be more reliable in a more static measurement scenario, while the other excels in highly dynamic ones. Several comparative experiments are presented, which identify a significant error source in the phase measurement induced by polarization rotation. Since the same effect may be induced by Faraday rotation, the results may have direct consequence on the design of the ITER dispersion interferometer/polarimeter as well as the European DEMO's interferometer concept. [ABSTRACT FROM AUTHOR]

This paper investigates the Faraday effect and absorption and luminescence spectra of single-crystal TbF3 measured at 90 K and 300 K. The optical-quality single-phase TbF3 crystals (structural type β-YF3) were grown by the Bridgman technique. Faraday rotation angles were measured at remagnetization along the [100] crystallographic axis. Low temperature optical measurements were carried out along the [100] axis. "Quasi-doublet" sublevels with energy at 0 cm-1, 65 cm-1, and 190 cm-1, and also a singlet sublevel with energy at 114 cm-1 located in the ground 7F6 multiplet were determined from the low temperature luminescence spectra. The Van-Vleck behavior of the magnetic susceptibility χb can be satisfactorily explained by the magnetic mixing of wave functions belonging to the ground and first excited "quasi-doublet" sublevels at 0 and 65 cm-1, respectively. Analysis of the oscillation dependences of the rotation angle showed that the value of the natural birefringence (Δn ≈ 0.0186) remains nearly constant within the wavelength and temperature ranges under investigation. As the temperature decreases, we find significant increases in the oscillation amplitude of the rotation angle and in the Verdet constant V. The spectral dependences V(χ) are linear throughout the temperature range. The magnetooptical activity of TbF3 can be explained by means of the spin- and parity-allowed electric-dipole 4f → 5d transitions in the Tb3+ ions. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel method to test the Einstein equivalence principle (EEP) using (simultaneous) multi-wavelength radio observations of polarized blazars. We analyse simultaneous multi-wavelength polarization observations of 3C 279 at 22, 43, and 86 GHz obtained by two antennas of the Korean VLBI Network. We obtained 15 groups of polarization data, and applied the Metropolis–Hastings Markov chain (MHMC) to simulate the parameters when considering the EEP effect and the simplest form of Faraday rotation (single external Faraday screen). The final results show the constraint of the parametrized post-Newtonian (PPN) parameter γ discrepancy as Δγp = (1.91 ± 0.34) × 10−20. However, the single external Faraday screen is an oversimplification for blazars because there are numerous observations showing complex Faraday rotation behaviour for blazars due to internal/external Faraday dispersion, beam depolarization, etc. The Δγp results of this paper can only be considered as upper limits. Only if all other effects are revealed and considered should the result be taken as a direct measurement of the violation of the EEP. [ABSTRACT FROM AUTHOR]

The utilization of a bismuth-substituted iron garnet as a magnetooptic Faraday rotator (MOFR) has been reported for all-optical networking purposes as well as for other applications. Our measurements and observations demonstrate that the MOFR saturates once a significantly large magnetic field (>225 G) is applied. After the applied magnetic field enters the saturation region, the material’s magnetic domains can become pinned at intermediate levels of magnetization. Pinning in this form has not been reported nor well studied for this application. In this paper, a method to detect and describe anomalous pinning in terms of Faraday rotation is presented. Measurements on the changes in the state of polarization that a pinned material produces are examined. This paper will also present practical methods for unpinning the MOFR material, which are traditionally considered to be challenging. [ABSTRACT FROM AUTHOR]

Bi-doped rare earth iron garnet (Bi:RIG) crystal is an ideal magneto-optical material for optical isolators in the near-infrared band, which has been widely used in optical communication applications. In this paper, centimeter-sized and good-quality Ni2+-doped Bi:RIG crystals were successfully grown by top-seeded solution growth (TSSG). The transmittance reaches 72.6% at 1550 nm, which is higher than commercial Bi:TbIG crystal and close to the theoretical values of RIG crystals. Doping Ni can not only greatly improve the transmittance, magnetic, and magneto-optical properties, but also decrease the Faraday rotation temperature (FTC) and wavelength coefficients (FWC) of the Bi:RIG crystal. The FTC and FWC of (Bi 0.37 Ho 1.18 Eu 0.83 Gd 0.62)(Fe 4.20 Ni 0.25 Ga 0.55)O 12 crystal reduced to − 6.3 × 10−4 K−1 and 8.0 × 10−4 nm−1, which are about 30% and 80% of commercial Bi:TbIG crystal, respectively. (Bi 0.37 Ho 1.18 Eu 0.83 Gd 0.62)(Fe 4.20 Ni 0.25 Ga 0.55)O 12 exhibits potential for utilization in new high-performance, wideband magneto-optical isolators, and is expected to find application in the field of wavelength division multiplexing fiber communication. • Ni2+ doping greatly improved the optical transmittance of Bi:(HoEu)IG crystal. • Low-content Ni2+ crystals have excellent magnetic and magneto-optical properties, with θ F of − 451 deg. cm−1. • FTC and FWC of Ni2+ doping crystal dramatically decrease to about 30% and 80% of commercial crystal, respectively. [ABSTRACT FROM AUTHOR]

The phenomenon of Faraday rotation of linearly polarized synchrotron emission in a magneto-ionized medium has been understood and studied for decades. But since the sense of the rotation itself is irrelevant in most contexts, some uncertainty and inconsistencies have arisen in the literature about this detail. Here, we start from basic plasma theory to describe the propagation of polarized emission from a background radio source through a magnetized, ionized medium in order to re-derive the correct sense of Faraday rotation. We present simple graphics to illustrate the decomposition of a linearly polarized wave into right and left circularly polarized modes, the temporal and spatial propagation of the phases of those modes, and the resulting physical rotation of the polarization orientation. We then re-examine the case of a medium that both Faraday rotates and emits polarized radiation and show how a helical magnetic field can construct or destruct the Faraday rotation. This paper aims to resolve a source of confusion that has arisen between the plasma physics and radio astronomy communities and to help avoid common pitfalls when working with this unintuitive phenomenon. [ABSTRACT FROM AUTHOR]

In flows of dry particulate systems, electric charge is generated on particle surfaces by their collision with walls and with other particles. Charge build-up on single particles can yield local charge values high enough to surpass the limiting electric field for corona discharge into the surrounding gas. Then, local charge is decreased to a lower value that becomes stabilized when flows stop and particles deposit in a container. In this paper, we have used a Faraday pail system to measure the residual particle charge after using two different devices—tribochargers—for particle charging. One of the tribochargers allowed us to directly measure the total charge that was transferred from the walls to the particles, and this was compared to the final values in the bulk powder once it was collected in the Faraday pail. The results show that the electric charge of particles dispersed in gas is limited by corona discharge and depends mainly on the particle size. In addition, we present a simple model of the discharge of the collected powder based on electrostatic considerations. If the powder effective conductivity and the electric charge of the settling particles are known, the model predicts the temporal evolution of the total charge of the collected powder and the spatial distribution of the electric charge and electric field. [ABSTRACT FROM AUTHOR]

We describe the ongoing Relativistic Binary programme (RelBin), a part of the MeerTime large survey project with the MeerKAT radio telescope. RelBin is primarily focused on observations of relativistic effects in binary pulsars to enable measurements of neutron star masses and tests of theories of gravity. We selected 25 pulsars as an initial high priority list of targets based on their characteristics and observational history with other telescopes. In this paper, we provide an outline of the programme, and present polarization calibrated pulse profiles for all selected pulsars as a reference catalogue along with updated dispersion measures. We report Faraday rotation measures for 24 pulsars, twelve of which have been measured for the first time. More than a third of our selected pulsars show a flat position angle swing confirming earlier observations. We demonstrate the ability of the Rotating Vector Model, fitted here to seven binary pulsars, including the Double Pulsar (PSR J0737–3039A), to obtain information about the orbital inclination angle. We present a high time resolution light curve of the eclipse of PSR J0737–3039A by the companion's magnetosphere, a high-phase-resolution position angle swing for PSR J1141–6545, an improved detection of the Shapiro delay of PSR J1811–2405, and pulse scattering measurements for PSRs J1227–6208, J1757–1854, and J1811–1736. Finally, we demonstrate that timing observations with MeerKAT improve on existing data sets by a factor of, typically, 2–3, sometimes by an order of magnitude. [ABSTRACT FROM AUTHOR]

The photon-spin-dependent (PS) contribution to the ordinary Faraday effect—optical rotation in an external magnetic field is well known. This contribution is proportional to factor where is the photon spin. Recently a -odd Faraday effect—optical rotation in an external electric field —was discussed as a promising tool for observation of the electron electric dipole moment in the intra-cavity absorption spectroscopy. In the present paper, we introduce the PS contribution to the -odd Faraday rotation effect. This contribution is proportional to and has to be taken into account in the calculations of the -odd Faraday effect. [ABSTRACT FROM AUTHOR]

An Unmanned Aerial Vehicle (UAV) commonly known as a drone or an Unmanned Aircraft System (UAS) is an aircraft without a human pilot aboard. UAV requires links to be established for communications such as telemetry (Video telemetry-First Person View (FPV)), telecommand (GPS) and flight command (RF Control). Antennas are an essential part of remote control of UAVs. The antennas used in UAVs must have small form factor, should not affect the UAV aerodynamic characteristics and at the same time, improve the power management efficiency by providing high gain and directional radiation pattern. The most common frequencies used for FPV video transmission are 900 MHz, 1.3, 2.4, and 5.8 GHz. The image resolution of FPVs is affected by the penetration depth of waves and hence the highest ISM band frequency of 5.8 GHz is preferred for FPV transmission systems. In a broad sense, antennas that were designed for 5.8GHz fall under either a linear polarizing (LP) antenna or a circular polarizing (CP) antenna. LP antennas are constituted mainly by structures like normal dipole, monopole, blade dipole and also disposable structures like inkjet-printed Yagi antennas. The family of circularly polarized antenna can be classified as derivative from LP antennas and Dielectric resonator antenna (DRA) structures. The former one includes structures like stacked loop antennas, cloverleaf antennas etc., while the latter one provides a vast degree of designing freedom and parametric advantages that are held by DRA over conventional antenna structures. Omnidirectional circularly polarized (CP) antennas have received more attention compared with linear polarized (LP) antennas due to several key advantages such as reducing the Faraday rotation effect, suppressing multipath reflection and eliminating the receiver-transmitter synchronizing problem. CP permits a maximum degree of freedom of choice in antenna position. This paper gives an extensive review of antennas and modern flight controlling techniques that are used in FPV based UAV applications. Both linear and circular polarized antennas as well as the scanning technique that are used in finding field patterns for UAV platforms are reviewed. [ABSTRACT FROM AUTHOR]

• Mn x Fe 1−x Fe 2 O 4 ferrofluids prepared by chemical co-precipitation reaction. • Mn2+ substitution affects the Faraday's rotation and shifts the optical band to blue region. • Mn x Fe 1−x Fe 2 O 4 exhibited increased toxicity to cancer cells with increasing particle concentration. Aqueous manganese (Mn)-doped magnetite is an interesting candidate for cancer therapy owing to its unique magnetic, optical, and viscosity properties and its response to an external magnetic field. This paper addresses the preparation of manganese-doped magnetite ferrofluids Mn x Fe 1-x Fe 2 O 4 (x = 0 to 0.8) by a chemical co-precipitation reaction with tetramethylammonium hydroxide surfactant for their potential application in cancer therapy. Mn-doped magnetite is analyzed for its magneto-viscosity and magneto-optical behaviors as a function of composition. Our findings show enhancements in viscosity, density, and optical properties with increasing particle concentration under the influence of an external magnetic field. Raman spectroscopic analysis of Mn x Fe 1-x Fe 2 O 4 shows characteristic peak shifts at 303, 474 and 680 cm−1 corresponding to MnFe 2 O 4. Interestingly, the Faraday rotation response is influenced largely by the external field upon increasing the composition of ferrofluids, making them ideal for targeted therapy and nano-therapeutic applications. Mn x Fe 1-x Fe 2 O 4 exhibited increased toxicity to cancer cells compared to normal cells with increasing particle concentration, which is well in alignment with its functional properties. Furthermore, the study also presents the scope for its use as a localized treatment of tumors with maximum tissue retention upon skin permeation for 24 h. Thus, our results clearly demonstrate the fine tuning of magneto-optical properties by manganese doping of ferrofluids without compromising their biocompatibility or imparting anti-cancer activity. [ABSTRACT FROM AUTHOR]

• A method for solving the problem of diffraction by a "gray" slit is proposed. • The two-domain structure of a transparent ferromagnet is considered as an example of a "gray" slit. • Light diffraction by a dynamic domain wall can be used to study dynamics with high spatial resolution. • The use of light diffraction in high-speed photography and pump–probe techniques opens up new experimental possibilities. It is known that the use of light diffraction makes it possible to improve the spatial resolution of magneto-optical methods. The image of a two-domain structure obtained in the domain wall contrast makes it possible to consider such a structure as a "gray" slit. In this paper, we consider the problem of light diffraction by a "gray" slit and discuss the possibilities of using the obtained results in high-speed photography and in the pump–probe method. [ABSTRACT FROM AUTHOR]

Incompatibility of conventional magneto‐optical (MO) materials with photonic‐system fabrication processes constitutes a major technological roadblock limiting their integration into photonic devices, especially for micro‐ or nano‐patterned films. This paper proposes a photolithography approach toward MO micro‐ and nano‐patterns, based on hybrid photosensitive matrices doped with magnetic nanoparticles to concentrations as high as 20 % vol. The as‐prepared and characterized nanocomposite thin films exhibit excellent MO properties: a high Faraday rotation (3300°/cm), comparable with the best existing materials that nevertheless require much more involved processes. The photosensitive matrices allow patterned gratings with a wide range of periods (100 μm to 500 nm), using a simple procedure at room temperature. The fabricated gratings exhibit well‐defined regular structures and resolutions suitable for optical applications, including those at telecommunications wavelengths. Finally, direct applications of the proposed material and its associated process are demonstrated on two examples: 1) a magneto‐optical grating in free‐space and 2) in combination with a waveguide. The obtained optical and MO results are consistent with simulations. [ABSTRACT FROM AUTHOR]

The observed time delays between photons with different circular polarizations from an astrophysical object provide a new, interesting way of testing the Einstein Equivalence Principle (EEP). In this paper, we constrain the EEP by considering both Shapiro time delay and Faraday rotation effects. We continue to search for astronomical sources that are suitable for testing the EEP accuracy, and obtain 60 extragalactic radio sources with multiwavelength polarization angles in three different radio bands (20, 8.6, and 4.8 GHz) and 29 brightest stars within our own Milky Way galaxy with multicolour linear polarimetric data in five optical bands (UBVRI). We apply the Metropolis–Hastings Markov Chain to simulate the fit parameters. The final results show that the values of the parametrized post-Newtonian parameter γ discrepancy (Δγp) are constrained to be in the range of 10−26 − 10−23 for 60 radio sources and in the range of 10−23 − 10−20 for 29 optical polarization stars. Compared to previous EEP tests that based on the single polarization measurement in the gamma-ray band, our results have profound superiority that nearly a few tens of astrophysical sources with multiwavelength polarization observations commonly in the optical and radio bands are available. It ensures that these sources can give more significantly robust bounds on the EEP. Although the presented method is straightforward, the resulting constraints on the EEP should be taken as upper limits as other more complex astrophysical effects affecting a polarization rotation are hardly considered. [ABSTRACT FROM AUTHOR]

This paper focuses on analytical methods of a finite-element method (FEM)-based edge heating system. The edge heating system plays a role in maintaining the temperature in the hot rolling process of carbon steel. Carbon steel moves along the production line and maintains the temperature by the edge heating system in the process. Power-of-the-edge heating system is transmitted to carbon steel during the process. Eddy currents are generated in carbon steel by Faraday’s law of electromagnetic induction, and eddy current loss serves as a heat source to increase the temperature. Thus, there is a need for accurate electromagnetic-field analysis and thermal analysis because the eddy current path generated in carbon steel greatly affects the heat distribution in carbon steel. This multiphysics analysis requires high reliability. Accordingly, this paper presents a coupling analysis method using an FEM-based coordinate mapping method as a more accurate analytical method. This paper also established an analytical approach to the edge heating system using the ductility analytical method of this coordinate mapping method. [ABSTRACT FROM AUTHOR]

The paper presents the design of sub‐wavelength high‐performing nonreciprocal optical devices using recently discovered magnetic Weyl semimetals. These passive bulk topological materials exhibit anomalous Hall effect which results in magneto‐optical effects that are orders of magnitude higher than those in conventional materials, without the need of any external magnetic bias. Two optical isolators of both Faraday and Voigt geometries are designed. The isolators have dimensions that are reduced by three orders of magnitude compared to conventional magneto‐optical configurations. The designed structures demonstrate that the magnetic Weyl semimetals may open up new avenues in photonics for the design of various nonreciprocal components. [ABSTRACT FROM AUTHOR]

We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest resolution images of NGC 6251 at these frequencies to date, revealing for the first time a low-surface-brightness extension to the northern lobe, and a possible backflow associated with the southern lobe. The integrated spectra of components of NGC 6251 are consistent with previous measurements at higher frequencies, similar to results from other LOFAR studies of nearby radio galaxies. We find the outer structures of NGC 6251 to be either at equipartition or slightly electron dominated, similar to those of FRII sources rather than FRIs, but this conclusion remains tentative because of uncertainties associated with the geometry and the extrapolation of X-ray measurements to determine the external pressure distribution on the scale of the outer lobes. We place lower limits on the ages of the extension of the northern lobe and the backflow of the southern lobe of t ≳ 250 Myr and t ≳ 210 Myr, respectively. We present the first detection of polarization at 150 MHz in NGC 6251. Taking advantage of the high Faraday resolution of LOFAR, we place an upper limit on the magnetic field in the group of |$B \lt 0.2 \, (\Lambda _B / 10\, {\rm kpc})^{-0.5}\, \mu$| G for a coherence scale of |$\Lambda _B \lt 60\, {\rm kpc}$| and |$B \lt 13\, \mu \textrm{G~for} \Lambda _B = 240$|  kpc. [ABSTRACT FROM AUTHOR]

In this paper, we experimentally study the saturation effect of rubidium atomic magnetic resonance. A pump beam is applied to create atomic spin polarization, a radio frequency (RF) magnetic field is used to drive the spin precession about a static magnetic field, and an off-resonant linearly polarized probe beam is applied to detect the spin dynamics based on the Faraday-rotation effect. When the RF magnetic field intensity becomes strong, a saturation effect is observed. We measure the resonant peak under strong RF magnetic field driving and obtain a saturation dip as an indication of the saturation effect. Furthermore, we show that the line-width of the saturation dip is much smaller than that of magnetic resonance. Accordingly, the sensitivity of the precision measurement based on the saturation dip can be significantly improved. The relations between the saturation dip in the resonant peak and the driving RF magnetic field intensity, as well as pumping intensity, are also studied in our experiment. [ABSTRACT FROM AUTHOR]

A laser ion source coupled with a radio frequency quadrupole linac accelerator is being proposed as a suitable system for the production of a low energy, high-current stable lithium beam. In order to maximize the lithium yield, plasmas generated by laser ablation of different materials based on lithium (Li, LiOH, and LiNbO3) have been characterized by using a Faraday cup and an electrostatic ion analyzer in the time of flight configuration. A wide range of laser power density has been investigated (109–1012 W/cm2) using two Nd:YAG lasers operating at different wavelengths (1064 nm and 532 nm), pulse durations (6 ns and 17 ns), and maximum energies (1400 mJ and 210 mJ). This paper outlines the pros and cons of the investigated materials by studying how the ion energy, yields, and charge state distributions are modified when the laser power density is changed. Considerable attention has been paid to the higher charge states of oxygen, which may occur with the same mass-to-charge ratio of Li3+. The analysis has evidenced that LiNbO3 represents a valid target since it allows minimizing the O6+/7Li3+ ratio down to 2.5% by using a laser power density of 1.8 × 1010 W/cm2. For such a condition, a Li3+ current of 1.4 mA/cm2 has been measured. [ABSTRACT FROM AUTHOR]

This paper presents the calibration and validation studies for the Radio Occultation and Heavy Precipitation experiment aboard the PAZ satellite. These studies, necessary to assess and characterize the noise level and robustness of the differential phase shift (ΔΦ) observable of polarimetric radio occultations (PROs), confirm the good performance of the experiment and the capability of this technique in sensing precipitation. It is shown how all the predicted effects that could have an impact into the PRO observables (e.g., effect of metallic structures nearby the antenna, the Faraday rotation at the ionosphere, signal impurities in the transmission, and altered cross-polarization isolation) are effectively calibrated and corrected, and they have a negligible effect on the final observable. The on-orbit calibration, performed using an extensive dataset of free-of-rain and low-ionospheric activity observations, is successfully used to correct all the collected observations, which are further validated against independent precipitation observations confirming the sensitivity of the observables to the presence of hydrometeors. The validation results also show how vertically averaged ΔΦ can be used as a proxy for precipitation. [ABSTRACT FROM AUTHOR]

The present paper describes reduction procedures and imaging of radio astronomical data from the gravitational lens system CLASS B0631+519 acquired by e-MERLIN interferometer. The source has been previously imaged with VLA, MERLIN and the VLBA interferometers. Data reduction and polarisation calibration procedures will provide data on Faraday effects such as Faraday rotation and depolarization between lensed images that in turn carry information on large and small-scale magnetic fields in the lensing galaxy. Reduction of data and imaging of the radio astronomical source have been achieved using Astronomical Image Processing System (AIPS) in conjunction with automatic data reduction pipelines that performed specific data processing steps. As a result, the sky map for the gravitational lens system has been successfully acquired and accuracy comparing the generated map to sky maps of the source produced by different authors has been confirmed. [ABSTRACT FROM AUTHOR]

Faraday rotation measure (RM) at radio wavelengths is commonly used to diagnose large-scale magnetic fields. It is argued that the length-scales on which magnetic fields vary in large-scale diffuse astrophysical media can be inferred from correlations in the observed RM. RM is a variable which can be derived from the polarized radiative transfer equations in restrictive conditions. This paper assesses the usage of rotation measure fluctuation (RMF) analyses for magnetic field diagnostics in the framework of polarized radiative transfer. We use models of various magnetic field configurations and electron density distributions to show how density fluctuations could affect the correlation length of the magnetic fields inferred from the conventional RMF analyses. We caution against interpretations of RMF analyses when a characteristic density is ill defined, e.g. in cases of lognormal-distributed and fractal-like density structures. As the spatial correlations are generally not the same in the line-of-sight longitudinal direction and the sky plane direction, one also needs to clarify the context of RMF when inferring from observational data. In complex situations, a covariant polarized radiative transfer calculation is essential to capture all aspects of radiative and transport processes, which would otherwise ambiguate the interpretations of magnetism in galaxy clusters and larger scale cosmological structures. [ABSTRACT FROM AUTHOR]

This paper studies how to employ synchrotron emission gradient techniques to reveal the properties of the magnetic field within the interstellar media. Based on data cubes of three-dimensional numerical simulations of magnetohydrodynamic turbulence, we explore spatial gradients of synchrotron emission diagnostics to trace the direction of the magnetic field. According to our simulations, multifarious diagnostics for synchrotron emission can effectively determine the potential direction of projected magnetic fields. Applying the synergies of synchrotron diagnostic gradients to the archive data from the Canadian Galactic Plane Survey, we find that multifarious diagnostic techniques make consistent predictions for the Galactic magnetic field directions. With the high-resolution data presently available from Low Frequency Array for radio astronomy and those in the future from the Square Kilometer Array, the synergies of synchrotron emission gradients are supposed to perform better in tracing the actual direction of interstellar magnetic fields, especially in the low-frequency Faraday rotation regime where the traditional synchrotron polarization measure fails. [ABSTRACT FROM AUTHOR]

The anomalous physical properties of dysprosium iron garnet Dy3Fe5O12 or DyIG single crystals have been revisited at low temperatures. This paper presents results of experimental investigation based on specific heat, magnetization, and Faraday rotation measurements. The distinguishing features are the occurrence of two types of anomalies in the temperature dependences of some judicious quantities. The first one coincides with the previous first-order spin reorientation transition at TSR = 15 K where the iron sublattice magnetization vector MFe changes from the <111> axis at high temperature toward the low angular phases below TSR. The second one takes place around the "low-temperature Belov point" TB = 42 K, confirming what had already been predicted previously about the paraprocess effect in this ferrimagnet. The results are compared with previous findings and discussed taking into account the coexistence of some concomitant phenomena such the magnetodielectric and Schottky effects which cause anomalies, respectively near TSR and TB. [ABSTRACT FROM AUTHOR]