Field Strength Measurements Research Articles

Polarised radio pulsations from a new T-dwarf binary

Brown dwarfs display Jupiter-like auroral phenomena such as magnetospheric Hα emission and coherent radio emission. Coherent radio emission is a probe of magnetospheric acceleration mechanisms and it provides a direct measurement of the magnetic field strength at the emitter’s location, both of which are difficult to access by other means. Observations of the coldest brown dwarfs (spectral types T and Y) are particularly interesting as their magnetospheric phenomena may be very similar to those in gas-giant exoplanets. Here we present 144 MHz radio and infrared adaptive optics observations of the brown dwarf WISEP J101905.63+652954.2 made using the Low Frequency Array (LOFAR) and Keck telescopes, respectively. The radio data show pulsed, highly circularly polarised emission which yields a rotation rate of 0.32 ± 0.03 h−1. The infrared imaging reveals the source to be a binary with a projected separation of 423.0 ± 1.6 mas between components of spectral type T5.5 ± 0.5 and T7.0 ± 0.5. With a simple ‘toy model’, we show that the radio emission can, in principle, be powered by the interaction between the two dwarfs with a mass-loss rate of at least 25 times the Jovian value. WISEP J101905.63+652954.2 is interesting because it is the first pulsed methane dwarf detected in a low radio-frequency search. Unlike previous gigahertz-frequency searches that were only sensitive to objects with kiloGauss fields, our low-frequency search is sensitive to surface magnetic fields of ≈50 G and above which might reveal the coldest radio-loud objects down to planetary mass scales.

A VARIANT FOR USING REGRESSION ANALYSIS TO ASSESS THE ELECTROMAGNETIC ENVIRONMENT IN AN URBAN AREA

The current study was conducted by making a series of experimental measurements of the electric field strength E. The obtained results have been interpreted using the method of mathematical modelling because the object of study – electromagnetic environment (EME) is a multifactorial system. With the accepted limitation of considering the influence of only two factors (frequency and time intervals) a two-factor regression analysis was used. The processing of the obtained data was performed by two-dimensional quadratic objective function.

Impact of Antenna Tilt on Measurements Below 1 GHz in Semi-Anechoic Chamber

The conditions of measurement of radio disturbance emission are defined in EN 55016-2-3 standard. It defines the detailed requirements of the measuring system and the methodology of the test. In case of the measurement up to 1 GHz the antenna height scan is required but there is no regulation regarding the antenna tilt in current edition of standard. As a result most laboratories perform measurements of radiated emission with a fixed antenna angle of 0∘ -the antenna is located in parallel with the ground plane despite the actual height. Knowing that the antenna inclination angle in relation to the emission source affects its characteristics, it can lead to omit the measurement configuration at which the measured field strength is the highest. The article investigates the influence of receiving antenna inclination angle on measurements of radiated disturbances from a reference emission source and real TV-set.

Analysis of Field Uniformity in a TEM Cell Based on Finite Difference Method and Measured Field Strength

Analysis of Field Uniformity in a TEM Cell Based on Finite Difference Method and Measured Field Strength

Analytical Comparison of Path Loss Models for Radio Wave Propagation over Yenagoa–Southern Nigeria

Using propagation models helps with communication system planning and maximizes the use of the radio spectrum, a limited natural resource. Here is a comparative analysis between some propagation models and actual measurements from Yenagoa, Southern Nigeria. Electric field strength measurements made during drive tests for two television transmitters operating at 210.25 MHz and 577.10 MHz make up the experimental data. Analytical comparisons were made between verified predictions for the free space, Okumura, and Hata models and measured data. The results demonstrate that these empirical models fail to take into account Yenagoa's actual terrain profile for television broadcast. The Okumura model is the best fit, with ideal values for root mean square error (RMSE) of 34.9136 and 33.2841 and average relative error of 0.13212 and 0.4327 for 210.25 MHz and 577.10 MHz, respectively. However, if the Okumura model is tailored for Yenagoa to improve electric field strength prediction and coverage estimation, better results can be attained.

The Analysis and Verification of IMT-2000 Base Station Interference Characteristics in the FAST Radio Quiet Zone

In this study, we aim to analyze the electromagnetic interference (EMI) regarding the Five-hundred-meter Aperture Spherical radio Telescope (FAST) caused by base stations in the International Mobile Telecommunications-2000 (IMT-2000) frequency band. By analyzing the frequency bands used by the transmitting and receiving devices and the surrounding environmental parameters and utilizing an approach to predicting radio wave propagation loss that is based on deterministic methods, we conclude by comparing the predicted received power at the FAST with its interference protection threshold. Our analysis demonstrates that, currently, only 55.31% of IMT-2000 base stations in the FAST radio quiet zone (RQZ) meet the protection threshold. Additionally, this article verifies the applicability and accuracy of the radio wave propagation model used in the research based on field strength measurements. Overall, this study provides valuable insights for improving the electromagnetic environment surrounding FAST and reducing the EMI caused by mobile communication base stations. It also provides corresponding analysis methods and useful suggestions for analyzing electromagnetic radiation interference in other radio telescopes.

Physical, optical and thermoluminescence properties of lithium aluminum borate glass co-doped with Dy2O3

The present study aimed to evaluate the physical, optical, and thermoluminescence (TL) properties of Li2O–Al2O3–B2O3 as a function of adding Dy2O3 dopant concentrations varying from 0.0 to 0.8 mol%. The glasses were produced through the melt-quenching technique. The optimal concentration of Dy3+ ions for the 4F9/2 → 6H11/2 and 4F9/2 → 6H15/2 transition was found to be at 0.8 mol%. The glassy nature of the quenched samples was confirmed by the XRD pattern. All samples have been subjected to measurements of various physical properties, including density, molar volume, Polaron radius, inter-nuclear distance, ion concentration, and field strength. The most optimal sample exhibited exceptional linearity within the dose range of 0.5–5.0 Gy during gamma irradiation. The un-doped and Dy3+ doped glasses exhibited a linear correlation coefficient of 0.446 and 0.995, respectively, while their tissue-equivalent effective atomic numbers were 7.4 and 10.5. Over the course of a month, the glasses exhibited a fading rate of only 15%. After being exposed to 3.0 Gy of gamma rays, the samples for minimum detectable dose and reproducibility were examined. The kinetic parameters of the glasses under investigation, such as activation energies and kinetics orders, were determined using the peak shape method. According to the findings, the sample that contained 0.8 mol% of Dy2O3 exhibited exceptional thermoluminescence characteristics, indicating its potential as a dosimeter for measuring exposure to ionizing radiation.

Evolution of coronal magnetic field parameters during X5.4 solar flare

The coronal magnetic field over NOAA Active Region 11,429 during a X5.4 solar flare on 7 March 2012 is modeled using optimization based Non-Linear Force-Free Field extrapolation. Specifically, 3D magnetic fields were modeled for 11 timesteps using the 12-min cadence Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager photospheric vector magnetic field data, spanning a time period of 1 hour before through 1 hour after the start of the flare. Using the modeled coronal magnetic field data, seven different magnetic field parameters were calculated for 3 separate regions: areas with surface |Bz|≥ 300 G, areas of flare brightening seen in SDO Atmospheric Imaging Assembly imagery, and areas with surface |B| ≥ 1000 G and high twist. Time series of the magnetic field parameters were analyzed to investigate the evolution of the coronal field during the solar flare event and discern pre-eruptive signatures. The data shows that areas with |B| ≥ 1000 G and |Tw|≥ 1.5 align well with areas of initial flare brightening during the pre-flare phase and at the beginning of the eruptive phase of the flare, suggesting that measurements of the photospheric magnetic field strength and twist can be used to predict the flare location within an active region if triggered. Additionally, the evolution of seven investigated magnetic field parameters indicated a destabilizing magnetic field structure that could likely erupt.

Магнитная система одноосного инерционного магнитожидкостного акселерометра

Today, a physical problem of engineering design of inertial magnetic fluid accelerometers to measure dynamic processes is relevant. The main drawback of modern sensors is the nonlinear characteristic of the forced response, which limits the application area of the sensors to the case of quasi-static action (tilt angle sensor). The reason of nonlinearity is the design of the magneto-mechanical system of the elastic suspension of the inertial mass made in the form of a pair of permanent ring magnets. This drawback can be eliminated by designing an axisymmetric electromagnetic system that generates a magnetic field with a linear intensity gradient along the symmetry axis. Thus, the paper is devoted to this problem and experimental approvement of the results on a laboratory sensor prototype. The Monte Carlo algorithm is used to calculate electromagnetic system containing permanent magnets and magnetizing coils. The algorithm is implemented using the C++ programming language. Measurements of the most important parameters of the magnetic field from the point of view of the purpose of the study are carried out on the assembled model of the electromagnetic system of the accelerometer. The calculation of electromagnetic system that generate permanent magnetic field with linear intensity gradient along the symmetry axis is carried out. The applicability of the Monte Carlo method to solve similar engineering problems is shown. The measurements of the magnetic field strength of a given configuration have been made. The force of the magnetic field acting on the test sensitive element with a constant magnetic moment is measured. A comparison of the calculated magnetic field with the field of a real system is carried out. It shows satisfactory agreement between the calculated data and the real ones. A linear dependence of the restoring force on the displacement coordinate of a body with a constant magnetic moment from the equilibrium position is shown. The linearization of the response of the mechanical part of the magnetic fluid accelerometer is achieved by choosing the desired configuration of its electromagnetic system, which allows making reliable measurements of both static and dynamic quantities.

SULIS: A coronal magnetism explorer for ESA’s Voyage 2050

Magnetism dominates the structure and dynamics of the solar corona. To understand the true nature of the solar corona and the long-standing coronal heating problem requires measuring the vector magnetic field of the corona at a sufficiently high resolution (spatially and temporally) across a large Field-of-View (FOV). Despite the importance of the magnetic field in the physics of the corona and despite the tremendous progress made recently in the remote sensing of solar magnetic fields, reliable measurements of the coronal magnetic field strength and orientation do not exist. This is largely due to the weakness of coronal magnetic fields, previously estimated to be on the order of 1-10 G, and the difficulty associated with observing the extremely faint solar corona emission. With the Solar cUbesats for Linked Imaging Spectro-polarimetry (SULIS) mission, we plan to finally observe, in detail and over the long-term, uninterrupted measurements of the coronal magnetic vector field using a new and very affordable instrument design concept. This will be profoundly important in the study of local atmospheric coronal heating processes, as well as in measuring the nature of magnetic clouds, in particular, within geoeffective Earth-bound Coronal Mass Ejections (CMEs) for more accurate forecasting of severe space weather activity.

Observation of strong terahertz field-induced second harmonic generation in plasma filaments.

We report the observation of terahertz field-induced second harmonic (TFISH) generation produced by directly mixing an optical probe beam onto femtosecond plasma filaments. The produced TFISH signal is spatially separated from the laser-induced supercontinuum by impinging on the plasma at a noncollinear angle. The conversion efficiency of the fundamental probe beam to its second harmonic (SH) beam is greater than 0.02%, which represents a record in optical probe to TFISH conversion efficiency that is nearly five orders of magnitude larger than previous experiments. We also present the terahertz (THz) spectral buildup of the source along the plasma filament and retrieve coherent terahertz signal measurements. This method of analysis has the potential to provide local electric field strength measurements inside of the filament.

Model of Cumulation of Man-Made Radio Noise, Applied to Sources of Emissions Limited by EMC Standards, and Compared With Noise Measurements

In this article, a theoretical model on the cumulation of noise, generated by large numbers of man-made noise (MMN) sources in several types of residential environments, has been developed. The model is based on extensive propagation measurements and verified by earlier field strength measurements. From applying the model it appears that MMN sources, emitting powers that equals mains port conductive disturbance limits in the electromagnetic compatibility standards, do not explain the measured noise field strength values. In contrary, the model indicates that the average source power is significant higher than can be derived from the limit in the standards. That could mean that the average power at the mains port is substantial higher than what generally is assumed. But alternately, the power, delivered by other ports like the ports for dc power, for telecom and for other wiring, is much higher than thought and could indicate a disregarded aspect in the electromagnetic compatibility (EMC) standards.

HF Noise Characteristics over Cyprus

Due to the long distance propagation characteristics of the HF spectrum, noise and interference are significant and challenging factors that have to be addressed in the context of HF system performance. Both aspects exhibit systematic diurnal, seasonal, and solar cycle variability that result in a number of corresponding measurement campaigns all over the globe, in an effort to characterise HF noise. Noise at HF consists of man-made and naturally occurring HF noise with atmospheric and galactic components. An understanding of HF noise variation in terms of time, azimuth, and filter bandwidth is crucial for a specific location, as it can provide a background knowledge based on which appropriate values of HF system parameters may be selected. This paper deals with the temporal, azimuthal, and bandwidth characteristics of HF noise based on a one-month dataset of electric field strength measurements recorded by a directional antenna in Cyprus.

The Effects of Sheet Thickness and Excitation Frequency on Hysteresis Loops of Non-Oriented Electrical Steel.

The paper focuses on modeling the rate dependence of hysteresis loops in conductive magnetic materials. The concept, which was advanced about fifty years ago by Chua, is discussed. It is shown that the viscous-type equation considered by Zirka and co-workers belongs to the class of Chua-type models. The dynamic effects are described with a simple fractional power law. The value of the exponent in the above-mentioned power law may be assessed on the basis of measurements of coercive field strength at different excitation frequencies. To verify the usefulness of the approach, the measurements of hysteresis loops were carried out at several excitation frequencies under standardized conditions for two grades of non-oriented electrical steel. The modeled curves are in a good correspondence with the measured ones. The considered model uses fewer parameters than approaches based on three-term loss separation schemes.

Magnetic fields of 30 to 100 kG in the cores of red giant stars.

A red giant star is an evolved low- or intermediate-mass star that has exhausted its central hydrogen content, leaving a helium core and a hydrogen-burning shell. Oscillations of stars can be observed as periodic dimmings and brightenings in the optical light curves. In red giant stars, non-radial acoustic waves couple to gravity waves and give rise to mixed modes, which behave as pressure modes in the envelope and gravity modes in the core. These modes have previously been used to measure the internal rotation of red giants1,2, leading to the conclusion that purely hydrodynamical processes of angular momentum transport from the core are too inefficient3. Magnetic fields could produce the additional required transport4-6. However, owing to the lack of direct measurements of magnetic fields in stellar interiors, little is currently known about their properties. Asteroseismology can provide direct detection of magnetic fields because, like rotation, the fields induce shifts in the oscillation mode frequencies7-12. Here we report the measurement of magnetic fields in the cores of three red giant stars observed with the Kepler13 satellite. The fields induce shifts that break the symmetry of dipole mode multiplets. We thus measure field strengths ranging from about 30 kilogauss to about 100 kilogauss in the vicinity of the hydrogen-burning shell and place constraints on the field topology.

Evaluation of Electromagnetic Field Levels and Student Exposure at Aydın Adnan Menderes University Central Campus

With the effect of developing technology, humanity is constantly exposed to more electromagnetic fields. Regional studies are gaining importance for determining the possible problems. In this study, extremely low-frequency electromagnetic field (ELF-EMF) measurements were carried out in Aydın Adnan Menderes University Central Campus in areas where university students are frequently found, at 25 randomly selected points, in the region where high voltage lines pass and around transformers, and to evaluate the awareness of university students about the ELF-EMF they are exposed to. For this purpose, the necessary magnetic field and electric field strength measurements were made and a questionnaire was applied to determine the awareness level of the students. Results were evaluated by comparing them with the ICNIRP limit values. Accordingly, it has been concluded that Aydın Adnan Menderes University Central Campus can be accepted as a relatively safe area since electromagnetic field exposure values are within the ICNIRP safe limit values. In addition, as a result of the questionnaire, it was determined that the young people were conscious to a certain extent about ELF-EMF, but they did not pay attention to protect themselves against the possible effects of ELF-EMF. It is important to make the necessary initiatives in order to raise awareness of young people on this issue.

Pilot study of a new methodology to study the development of the blue bottle fly (Calliphora vomitoria) under exposure to radio-frequency electromagnetic fields at 5.4 GHz

Purpose Exposure of insects to radio-frequency electromagnetic fields (RF-EMFs) can have developmental effects. However, there is currently no clear understanding of the exposure level that can lead to such effects. Therefore, the goal of this study was to, for the first time, study the development of the Blue Bottle Fly (Calliphora vomitoria, CV) under exposure to RF-EMFs at 5.4 GHz, using both numerical RF-EMF dosimetry with anatomically accurate 3 D models of insects and an RF-EMF exposure experiment. Materials and Methods CV was chosen as a model organism in this study because CV’s development can be influenced thermally and CV’s pupal stage presents a window of several days in which immobile pupae can be exposed to RF-EMFs. The 5.4 GHz frequency was used because it allowed us the license-free operation of the exposure setup. Numerical, EM simulations with 3 D anatomically accurate models of CV, obtained using micro-CT scanning, were used in this study. These simulations enable the estimation of the absorbed power and the whole-body averaged specific absorption rate in CV during RF exposure experiments. An experiment with three exposure conditions was designed and executed in which 400 pupae were split into an exposed group that was placed inside the TEM cell for 48 h and concurrent control. Two exposure conditions used RF-EMF input power into the TEM cell at 5.4 GHz on two different levels. One exposure condition was sham exposure. Electric field strength measurements were used to validate the proper functioning of the exposure setups and to quantify the RF-EMF exposure of the control groups. Results and conclusions All studied groups of pupae – exposed to RF-EMFs, sham, and control groups- showed similar (evolutions of) masses, lengths and diameters during their development. The total rate of pupal emergence was reduced in one of the studied RF-EMF exposures in comparison to its concurrent control, while the other RF-EMF exposure and the sham exposure did not alter the total rate of pupal emergence. The sham exposure and the lowest of the two studied RF-EMF exposure conditions (19.4 V/m) caused a median delay in pupal emergence of 4 and 8 hours, respectively, in comparison to concurrent control groups. The higher studied exposure of 55 V/m caused a median relative acceleration in the development of 8 h.

An assessment of generating quasi-static magnetic fields using laser-driven “capacitor” coils

Over the previous decade, numerous experiments have been performed using a laser to drive a strong, quasi-static magnetic field. Field strength and energy density measurements of these experiments have varied by many orders of magnitude, painting a confusing picture of the effectiveness of these laser-driven coils (LDCs) as tools for generating consistent fields. At the higher end of the field energy spectrum, kilotesla field measurements have been used to justify future experimental platforms, theoretical work, and inertial confinement fusion concepts. In this paper, we present the results from our own experiments designed to measure magnetic fields from LDCs as well as a review of the body of experiments that have been undertaken in this field. We demonstrate how problems with prior diagnostic analyses have led to overestimations of the magnetic fields generated from LDCs.

Magnetic field measurement in TMC-1C using 22.3 GHz CCS Zeeman splitting

ABSTRACT Measurement of magnetic fields in dense molecular clouds is essential for understanding the fragmentation process prior to star formation. Radio interferometric observations of CCS 22.3 GHz emission, from the starless core TMC-1C, have been carried out with the Karl G. Jansky Very Large Array to search for Zeeman splitting of the line in order to constrain the magnetic field strength. Toward a region offset from the dust peak, we report a detection of the Zeeman splitting of the CCS 21–10 transition, with an inferred magnetic field of ∼2 mG. If we interpret the dust peak to be the core of TMC-1C, and the region where we have made a detection of the magnetic field to be the envelope, then our observed value for the magnetic field is consistent with a subcritical mass-to-flux ratio envelope around a core with supercritical mass-to-flux ratio. The ambipolar diffusion time-scale for the formation of the core is consistent with the relevant time-scale based on chemical modelling of the TMC-1C core. This work demonstrates the potential of deep CCS observation to carry out future measurements of magnetic field strengths in dense molecular clouds and, in turn, understand the role of the magnetic field in star formation.

The initial magnetic criticality of pre-stellar cores

ABSTRACT Direct observational measurements of the magnetic field strength in pre-stellar cores typically find supercritical mass-to-flux ratios, suggesting that the magnetic field is insufficient to prevent gravitational collapse. These measurements suffer from significant uncertainties; an alternative approach is to utilize the sensitivity of pre-stellar chemistry to the evolutionary history, and indirectly constrain the degree of magnetic support. We combine non-ideal magnetohydrodynamic simulations of pre-stellar cores with time-dependent chemistry and radiative transfer modelling, producing synthetic observations of the model cores in several commonly observed molecular lines. We find that molecules strongly affected by freeze-out, such as CS and HCN, typically have much lower line intensities in magnetically subcritical models compared to supercritical ones, due to the longer collapse time-scales. Subcritical models also produce much narrower lines for all species investigated. Accounting for a range of core properties, ages, and viewing angles, we find that supercritical models are unable to reproduce the distribution of CS and N2H+ line strengths and widths seen in an observational sample, whereas subcritical models are in good agreement with the available data. This suggests that despite presently having supercritical mass-to-flux ratios, pre-stellar cores form as magnetically subcritical objects.