Total Field Strength Research Articles

Radio emission from cosmic ray air showers: Simulation results and parametrization

We have developed a sophisticated model of the radio emission from extensive air showers in the scheme of coherent geosynchrotron radiation, providing a theoretical foundation for the interpretation of experimental data from current and future experiments. Having verified the model through comparison of analytic calculations, Monte Carlo simulations and historical experimental data, we now present the results of extensive simulations performed with our Monte Carlo code. Important results are the absence of significant asymmetries in the total field strength emission pattern, the spectral dependence of the radiation, the polarization characteristics of the emission (allowing an unambiguous test of the geomagnetic emission mechanism), and the dependence of the radio emission on important air shower and observer parameters such as the shower zenith angle, the primary particle energy, the depth of the shower maximum and the observer position. An analytic parametrization incorporating the aforementioned dependences summarizes our results in a particularly useful way.

Multiscale Magnetic Fields in Star‐forming Regions: Interferometric Polarimetry of the MMS 6 Core of OMC‐3

We present the first interferometric observations of linearly polarized emission toward the OMC-3 region of the Orion A cloud. We have observed the MMS 6 protostellar core at 1.3 mm with the Berkeley-Illinois-Maryland Association (BIMA) array, achieving a resolution of 43 × 30. We find that the polarization angle measured changes systematically across the core, orienting along a dust extension to the northwest. The polarization angle is oriented similarly to the 850 and 350 μm polarized emission measured by the SCUBA and Hertz polarimeters. A polarization hole is detected, as is typical of polarized emission data toward cores. Since the BIMA data are insensitive to structure on spatial scales of >40'', the emission detected is dominated by the core and not the integral-shaped filament in which it is embedded. Observations of CO J = 2-1 reveal CO emission potentially associated with the core, but no outflow signature is detected. Utilizing the Chandrasekhar-Fermi method, we have used the dispersion in the polarization vectors to estimate a field strength of 640 μG in the plane of the sky, assuming a corrective Q-factor of 0.5. Applying the recent measurement of the inclination of the field to the line of sight (Houde et al.), a total field strength of 680 μG is derived. Despite highly nonthermal line widths, the kinetic energy density is found to be insufficient to support this core against gravitational collapse. The magnetic energy density, when combined with the predominantly turbulent kinetic energy density, is comparable to the effects of gravity, but its value is highly dependent on the applied Q-factor to a degree that the core may be subcritical or supercritical. The preservation of the field geometry from large to small scales in this core is consistent with observations of a second protostellar core in a filamentary cloud in Orion B.

Radio emission from cosmic ray air showers

We present time-domain Monte Carlo simulations of radio emission from cosmic ray air showers in the scheme of coherent geosynchrotron radiation. Our model takes into account the important air shower characteristics such as the lateral and longitudinal particle distributions, the particle track length and energy distributions, a realistic magnetic field geometry and the shower evolution as a whole. The Monte Carlo approach allows us to retain the full polarisation information and to carry out the calculations without the need for any far-field approximations. We demonstrate the strategies developed to tackle the computational effort associated with the simulation of a huge number of particles for a great number of observer bins and illustrate the robustness and accuracy of these techniques. We predict the emission pattern, the radial and the spectral dependence of the radiation from a prototypical 1017 eV vertical air shower and find good agreement with our analytical results [CITE] and the available historical data. Track-length effects in combination with magnetic field effects surprisingly wash out any significant asymmetry in the total field strength emission pattern in spite of the magnetic field geometry. While statistics of total field strengths alone can therefore not prove the geomagnetic origin, the predicted high degree of polarisation in the direction perpendicular to the shower and magnetic field axes allows a direct test of the geomagnetic emission mechanism with polarisation-sensitive experiments such as LOPES. Our code provides a robust, yet flexible basis for detailed studies of the dependence of the radio emission on specific shower parameters and for the inclusion of additional radiation mechanism in the future.

Colloids in inhomogeneous external magnetic fields: particle tweezing, trapping and voidformation

Two-dimensional super-paramagnetic suspensions that are confined to a planar liquid–gasinterface and exposed to an inhomogeneous external magnetic field directed perpendicularto the interface are studied by extensive Monte Carlo computer simulations. The externalfield is a superposition of a homogeneous field and a localized inhomogeneity,modelled by a Gaussian function. The inhomogeneity causes two combined effectsthat compete against each other: it provides an external potential, modifying atthe same time the mutual interparticle repulsion. If the inhomogeneity enhancesthe strength of the homogeneous profile, the inhomogeneous field is a ‘magnetictweezer’ for low particle densities. At higher densities, on the other hand, thereis a small accumulation in the centre of the inhomogeneous field, which leadsto a depletion zone outside the inhomogeneity due to the mutual interparticlerepulsion. Very large inhomogeneities produce local crystallites surrounded by adepletion ring. If the inhomogeneity reduces the total field strength, particlesare repelled from the inhomogeneity and voids are generated in the suspension.Our predictions are of relevance to the direct transport of magnetic particlesand can be verified in real-space experiments of super-paramagnetic suspensions.

Optimization of a post-type spacer in a gas insulated system under three-dimensional conditions

This paper describes the optimization of a post-type spacer in a gas insulated system. The electric field calculation and the optimization have been performed in three-dimensional conditions. We have utilized the boundary element method to calculate the electric field distributions and the Marquardt method to improve the profile of the spacer so as to minimize the maximal electric field on the spacer surface. The optimization has been performed for spacers with cylindrical column, circular, and elliptical cross-sections, respectively. We have varied additional parameters, such as the permittivity of a spacer and the radius ratio of an inner conductor and a sheath. For elliptical cross-section spacers, the optimization has reduced the maximal value of the total field strength up to 35%, and the maximal value of the tangential field strength up to 56% compared with the respective maximal field without a spacer.

Ornithine Decarboxylase Activity in Tissues from Rats Exposed to 60 Hz Magnetic Fields, Including Harmonic and Transient Field Characteristics

Ornithine decarboxylase (ODC) activity is used widely as a biomarker for tumor promotion in animal model systems. Several previous studies have reported increases in ODC activity in tissues of rats exposed to 60 Hz magnetic fields. The goals of this study were to confirm these findings and to determine whether ODC activity is increased in tissues of animals exposed to magnetic fields containing complex metrics. Three experiments were conducted in male F344 rats. Each study included a sham control group and a group exposed to pure continuous 60 Hz fields (0.2 mT). Additional groups included animals exposed to randomly time-varying 60 Hz fields (range of 0.02 to 0.2 mT); intermittent 60 Hz fields (2 mT) with on-off cycles ranging from 5 s to 5 min; pure continuous 180 Hz fields (2 mT); 60 Hz fields with a superimposed 3rd harmonic (total field strength, 2 mT); 60 Hz fields with superimposed third, fifth, and seventh harmonics (total field strength, 2 mT); 60 Hz fields (2 mT) with superimposed transients; and randomly time-varying 60 Hz fields (range of 0.02 to 0.2 mT) with superimposed transients. After 4 weeks of exposure (18.5 h/day), eight animals per group were euthanized within 1 h of magnetic field deactivation. Homogenates of liver, kidneys, spleen, and brain were prepared from each animal, quick-frozen, and shipped for analysis by four independent laboratories. No consistent pattern of differences in the ODC activity among experimental groups was found either within a laboratory or among laboratories. The results do not support the hypothesis that exposure to extremely low frequency magnetic fields stimulates ODC activity.

A statistical study of large‐amplitude parallel electric fields in the upward current region of the auroral acceleration region

We present a survey of 64 direct observations of large‐amplitude parallel electric fields E∥ in the upward current region of the southern auroral acceleration zone, obtained by the three‐axis electric field experiment on Polar. These E∥ events range in amplitude from about 25 to 300 mV/m and represent a significant fraction of the total electric field strength (E∥/E⟂ ranges from ∼0.25 to O(10)). The E∥ structures, which tend to occur at the edges of oppositely directed (converging) pairs of perpendicular electric field structures (electrostatic shocks), have transverse (to the magnetic field) widths of ∼1.0–20 km at altitudes ranging from 0.8RE to 1.5RE, assuming the structures are stationary. The parallel potential drops associated with these large‐amplitude parallel electric fields are highly localized in altitude (e.g., tens of kilometers as opposed to thousands of kilometers). The amplitude of the parallel electric field shows a strong anticorrelation with the plasma density inferred from spacecraft potential measurements. We find no apparent correlation between the amplitude of the parallel electric field and altitudes sampled (between 0.8RE and 1.5RE), current density, and Kp, though there is a suggestion that the largest E∥/E⟂ ratios are confined to lower altitudes. Taking sampling biases into consideration, we find that the large parallel electric fields occur preferentially at higher values of Kp and within a thin layer centered about 1.28RE. A detailed analysis favors ambipolar effects over electron inertial effects as an explanation for the parallel electric field signatures.

Magnetic Fields in Star‐forming Molecular Clouds. V. Submillimeter Polarization of the Barnard 1 Dark Cloud

We present 850 μm polarimetry from the James Clerk Maxwell Telescope toward several dense cores within the dark cloud Barnard 1 in Perseus. Significant polarized emission is detected from across the mapped area and is not confined to the locations of bright cores. This indicates the presence of aligned grains and hence a component of the magnetic field in the plane of the sky. Polarization vectors detected away from bright cores are strongly aligned at a position angle of ~90° (east of north), while vectors associated with bright cores show alignments of varying orientations. There is no direct correlation between the polarization angles measured in earlier optical polarimetry toward Perseus and the polarized submillimeter thermal emission. Depolarization toward high intensities is exhibited but toward the brightest core reaches a threshold beyond which no further decrease in polarization percentage is measured. The polarized emission data from the interior envelope are compared with previously published OH Zeeman data to estimate the total field strength and orientation under the assumption of a uniform and nonuniform field component in the region. These results are rough estimates only as a result of the single independent detection of Zeeman splitting toward Barnard 1. The uniform field component is thus calculated to be 0 = 31 μG [±(0.52 - 0.01) - 0.86] in the case in which we have assumed the ratio of the dispersion of the line-of-sight field to the field strength to be 0.2.

Comparative Analysis of the Crystal Field Strengths of Trivalent f Ions in Matrices of Various Symmetries

A comparative analysis of the crystal fields for a number of matrices containing f ions was carried out in terms of the total crystal field strength parameter. A spectrochemical series of systems was constructed, which corresponds to the electronic level splittings for the central ion and shows how the degree of interaction of the f shell with the surrounding varies with the nature of the ligands and outer-sphere cations, as well as with the coordination number, symmetry type, and the metal-ligand interatomic distance.

ディスク型スペーサの形状最適化

The profile optimization of an insulator such as a spacer is very important in reducing the cost of power equipment. This paper describes the profile optimization of a disk-type spacer utilized in coaxial cylindrical power equipment. The optimization is based on making the electric field distribution as uniform as possible on the surface of a spacer. The Charge Simulation Method was used to calculate the electric field and the Marquardt Method was used as an optimization technique. The following optimization conditions were set on the spacer surface. a) Constant tangential component of the electric field(Et) b) Constant total electric field(Ea) In the case of b), profile optimization was achieved, where the total field strength diminished to about 60% of the maximum value in the corresponding coaxial cylindrical arrangement without a spacer.

Water Masers Diagnosing Postshocked Conditions in W49N

We present spectroscopic results of 146 water maser outbursts in W49N, obtained with the Metsahovi radio telescope at 22 GHz. We found the following characteristics: (1) Inside (outside) the velocity range of the dense ambient medium, the increase in flux density during an outburst is typically 104 Jy (103 Jy) and covers 1 order (2.5 orders) of magnitude. (2) The outburst durations closely trace space velocities of maser features. (3) Nonthermal velocity fluctuations produce variations in the line velocity of the maser features, which are comparable to the variations measured in the line width during outbursts. (4) There is no correlation between flux density and line width. Combining these data with Gwinn's VLBI results, notably obtained during the same time period and with the same velocity resolution, we were able to fix the free parameters in the shock model of Hollenbach & McKee and the maser model of Elitzur, Hollenbach, & McKee. This enabled a straightforward determination of some 20 shock and maser parameters including, among others, the following typical values: kinetic temperature 350 K, postshock density (3.6-8.7) × 108 cm-3, water abundance (1-5) × 10-4, water density (0.9-1.9) × 105 cm-3, water column density (2.2-7.9) × 1019 cm-2, preshock field strength 0.8-1.6 mG, and total postshock field strength 80-160 mG. A step-by-step presentation of our diagnostic method is given, and the relation between observations and model parameters is discussed. One uniquely powerful outburst feature during 1981-1983, hereafter referred to as the flare feature, showed also the narrowest line width (0.5 km s-1). Observations indicate that the velocity of this feature lies in the plane of the sky, whereas preshock and postshock magnetic fields are directed nearly along the line of sight. Consequently, Alfvenic wave fluctuations along the line of sight, and line width, are minimal, and a very high aspect ratio is achieved. Furthermore, the big flare feature stands out through its low space velocity, higher temperature (480 K), and larger preshock magnetic field strength (8.2 mG). These are naturally explained, if the big flare feature was located closer to the shock front than the other masers.

Evaluation of the Developmental Toxicity of 60 Hz Magnetic Fields and Harmonic Frequencies in Sprague-Dawley Rats

Experimental data suggest that exposure to the 50 and 60 Hz sinusoidal components of power-frequency magnetic fields (MFs) does not have an adverse impact on fetal development. However, the possible developmental toxicity of MF harmonics has not been investigated. This study was designed to determine whether exposure to 180 Hz MFs (third harmonic), alone or in combination with 60 Hz MFs, induces birth defects in Sprague-Dawley rats. Groups of sperm-positive dams (> or =20/group) were exposed for 18.5 h per day from gestation days 6 through 19 to (1) ambient MFs only (<0.0001 mT; sham controls); (2) 60 Hz MFs at 0.2 mT; (3) 180 Hz MFs at 0.2 mT; or (4) 60 Hz + 180 Hz MFs (10% third harmonic; total field strength = 0.2 mT). Litter size, litter weight, percentage live births, sex ratio, and number of resorption sites were determined for each dam, and gross external, visceral, cephalic and skeletal examinations were performed on all fetuses. MF exposure had no significant effects on litter size, litter weight, or fetal development. With the exception of common rib variants, the incidence of fetal anomalies was comparable in all groups. A small increase in the incidence of rib variants was seen in the group exposed to 60 Hz + 180 Hz MFs; however, the incidence of rib variants in this group was similar to that in historical controls from our laboratory. These data extend the existing database on developmental toxicity of MFs by demonstrating that exposure to 180 Hz MFs, either alone or superimposed on an underlying 60 Hz signal, does not induce biologically significant developmental toxicity. These data do not support the hypothesis that exposure to power-frequency MFs is an important risk factor for fetal development.

Dualisation of dualities II: twisted self-duality of doubled fields and superdualities

We introduce a doubled formalism for the bosonic sector of the maximal supergravities, in which a Hodge dual potential is introduced for each bosonic field (except for the metric). The equations of motion can then be formulated as a twisted self-duality condition on the total field strength G , which takes its values in a Lie superalgebra. This doubling is invariant under dualisations; it allows a unification of the gauge symmetries of all degrees, including the usual U-dualities that have degree zero. These “superdualities” encompass the dualities for all choices of polarisation ( i.e. the choices between fields and their duals). All gauge symmetries appear as subgroups of finite-dimensional supergroups, with Grassmann coefficients in the differential algebra of the spacetime manifold.

Monitoring of Electromagnetic Radiation from Cellular Base Stations in Kuwait

A survey of the radio frequency electromagnetic environment in Kuwait was carried out. The primary purpose of this survey was to monitor electromagnetic radiation (EMR) field strength levels emitted by cellular base stations installed and operated by the Kuwait Mobile Telecommunications Company (MTC). Measurements were made at 26 cellular-phone base stations, chosen as a representative sample to include 14 school sites, 2 residential sites, 2 hospital sites, 3 ministerial building sites, 3 commercial sites and I typical stand-alone site. On all the selected sites measurements were made with a spectrum analyser to determine the emission level in the frequency bands used by the base station transmitters (917-960 MHz). The results indicated that total field strength, specifically due to the MTC base stations, found in public access areas, varied generally between 0.05 and 1.13 V.m -1 . These values are in the order of between 40 and 800 times lower than the new pan-European CENELEC pre-standard ENV 50166-2 'Human Exposure to Electromagnetic Fields'. In terms of power density the highest observed value (0.34 μW.m -2 ) was more than a thousand times below the prescribed standards.

Magnetohydrodynamic Simulations of Alfvenic Pulse Propagation in Solar Magnetic Flux Tubes: Two‐dimensional Slab Geometries

Two-dimensional magnetohydrodynamic simulations are presented of the evolution of a nonlinear Alfven wave pulse in the region between the solar photosphere and corona. A magnetic field profile that incorporates the characteristic field spreading expected in flux tubes is used. The pulse is chosen initially to have a purely Alfvenic polarization and to extend over a limited horizontal distance. It is shown that as this pulse rises in the atmosphere, it becomes wedge-shaped. The part of the pulse at the center of the flux tube reaches the transition region first, with other parts arriving at a time that is determined by the history of the Alfven speed along the path of the wave. Since field lines that spread out from the center of the flux tube spend longer in the high-density photosphere and chromosphere, and also have a smaller total field strength, waves that travel along them will take longer to reach the corona. The nonlinearity of the Alfvenic pulse drives a plasma flow both parallel to the ambient magnetic field and in a direction normal to the field, owing to transverse modulation of the Alfvenic pulse. The pulse associated with this plasma flow is also wedge-shaped, but the actual shape is different from that of the Alfvenic pulse. Since these plasma flows are compressible, they propagate at a different characteristic speed from the Alfven waves, and so can reach the transition region either before or after the Alfven pulse, the precise result depending on the plasma parameters. As the compressible pulse moves upward, a finite-sized blob of chromospheric material is injected into the corona. The relevance of this to spicules and jets is discussed.

Particle growth and transport in silane plasma chemical vapour deposition

The model equations for particle formation, growth and transport were proposed for silane plasma chemical vapour deposition and were solved numerically. We included the plasma chemistry of silane, particle nucleation by cluster formation, aerosol dynamics and transport of chemical species and particles. The evolutions of gaseous species and particles along the reactor were presented for several conditions of process variables such as reactor pressure, total gas flow rate and electric field strength. To reduce the CPU time in numerical simulation, we used lower values of electric field strength in the sheath region then the actual values and analysed the effects of electric field strength qualitatively. It was found that the concentration profiles of positive ions show peaks at the centre of the plasma reactor, whereas most of the negative ions are located in the bulk plasma region owing to the electrostatic repulsion from the sheath region. Most of the particles in the plasma reactor are located around the sheath boundaries, owing to the balance of the electrostatic force and the ion drag force. As the reactor pressure increases, the contaminant concentration and diameter increase in the plasma reactor. The lower the total gas flow rate the higher the particle concentration and the larger the particle diameter. The particle concentration and diameter in the plasma reactor increase abruptly as the electric field strength in the sheath region increases.

In Vivo Brain Water Determination by T1 Measurements: Effect of Total Water Content, Hydration Fraction, and Field Strength

This work is concerned with the accurate quantification of brain water content under routine clinical conditions. Gelatin solutions of varying water content are first employed as a model of an edematous brain and longitudinal relaxation measurements are performed at proton Larmor frequencies of 5, 41, 63, and 100 MHz. These are followed with in vivo measurements in an experimental animal model of brain edema at 41 MHz. The results underscore the dominant role of total water content W in the relaxation process and verify the expected linearity between 1/T1 and 1/W. A scheme is presented and experimentally verified at 41 MHz for deducing the exact relationship of 1/T1 vs 1/W at any frequency. Knowledge of this relationship along with precise measurements of 1/T1 at a given field strength permits quantitative in vivo measures of brain water content to be obtained with a precision of about 0.01. It is concluded that routine, accurate, and noninvasive brain water measurements are possible by magnetic resonance imaging in a clinical environment.

Field distribution on an HVDC wall bushing during laboratory rain tests

An efficient countermeasure to suppress flashovers across high-voltage DC (HVDC) wall bushings is to make their surfaces hydrophobic. The measured electric fields along such a bushing under different environmental conditions are reported. A significantly reduced radial field strength has been found for the hydrophobic bushing. Moreover, the total field strength distribution becomes almost independent of the prevailing dry zone. The flashover voltage for bushings with a hydrophobic surface is therefore significantly increased.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design of a non-equisectored 20-electrode deflector for e-beam lithography using a field emission electron beam

Abstract In order to achieve good field homogeneity various equi- and non-equisectored deflectors were analysed numerically. The least inhomogeneity of a field for practicable realization was found with a non-equisectored 20-pole deflector (30mm in diameter, 1.528° gap width, 110mm in length). In a square of 6mm by 6mm the total field strength variation is 0.38% of the main component and 0.24% for the perpendicular component. The numerical results and the fabrication of the 20-pole deflector already incorporated in an e-beam lithography system with thermal field emission cathode are discussed.

Upgraded Norwegian magnetic observatories in the Arctic

A description is given of a new digital fluxgate magnetometer system to be run at the following stations in the Norwegian Arctic region: Ny-Ålesund, Bjørnøya, Jan Mayen, Ramfjordmoen, and the Auroral Observatory in Tromsø. Summaries of the annual quiet mean values of the H- and D-components as well as the total field strength F observed at Tromsø, Bjørnøya and Ny-Ålesund for the last decades are also presented. The magnetic field strength reached a maximum at all three stations in the period 1975–1977. The maximum was first reached at the northernmost station indicating a phase shift from north to south.