Dynamics of Magnetophotorefractive Wave Mixing

Abstract. The geoelectric field drives geomagnetically induced currents (GICs) in technological conductor networks, which can affect the performance of critical ground infrastructure such as electric power transmission grids. The three-dimensional (3-D) electric field at the Earth's surface consists of an external divergence-free (DF) part due to temporally and spatially varying ionospheric and magnetospheric currents, an internal DF part due to temporally and spatially varying telluric currents, and a curl-free (CF) part due to charge accumulation at ground conductivity gradients. We have developed a new method for estimating these contributions. The external and internal parts of the DF electric field are calculated from the time derivative of the external and internal parts of the observed ground magnetic field, respectively, using DF two-dimensional (2-D) spherical elementary current systems (SECSs). The horizontal surface CF electric field is calculated from the known surface DF electric field using coefficients that linearly relate the DF electric field to the CF electric field. The coefficients were obtained from the 3-D induction model PGIEM2G (Polynomial Galerkin Integral Equation Modelling in ElectroMagnetic Geophysics). The calculations are carried out in the time domain, and only two consecutive time steps of the observed magnetic field are needed to compute the surface electric field. The external part of the DF electric field is valid at and below the ionosphere, the internal part at and above the Earth's surface, and the CF part at the Earth's surface. A dense magnetometer network is a requirement for reliable results. The external and internal parts of the DF electric field are generally oppositely directed and have comparable amplitudes, both on the ground and in the ionosphere, indicating that both contributions are significant for the total DF electric field. The largest peaks of the total DF electric field tend to occur when either the external or internal contribution is temporarily suppressed. At a given location, a DF electric field with a given amplitude can result in a total surface electric field amplitude with a difference of orders of magnitude depending on the direction of the DF electric field with respect to the locally dominant conductivity gradient structure. The electric field calculation is computationally light, facilitating operational implementation of a near-real-time 3-D surface electric field monitoring and derivation of long electric field time series.

Recent laboratory and epidemiological results have stimulated interest in the hypothesis that human beings may exhibit biological responses to magnetic and/or electric field transients with frequencies in the range between 100 Hz and 100 kHz. Much can be learned about the response of a system to a transient stimulation by understanding its response to sinusoidal disturbances over the entire frequency range of interest. Thus, the main effort of this paper was to compare the strengths of the electric fields induced in homogeneous ellipsoidal models by uniform 100 Hz through 100 kHz electric and magnetic fields. Over this frequency range, external electric fields of about 25-2000 V/m (depending primarily on the orientation of the body relative to the field) are required to induce electric fields inside models of adults and children that are similar in strength to those induced by an external 1 microT magnetic field. Additional analysis indicates that electric fields induced by uniform external electric and magnetic fields and by the nonuniform electric and magnetic fields produced by idealized point sources will not differ by more than a factor of two until the sources are brought close to the body. Published data on electric and magnetic field transients in residential environments indicate that, for most field orientations, the magnetic component will induce stronger electric fields inside adults and children than the electric component. This conclusion is also true for the currents induced in humans by typical levels of 60 Hz electric and magnetic fields in U.S. residences.

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. This thesis describes an experimental and theoretical study on modal dispersal of information and wave mixing in photorefractive crystals for vector phase conjugation and real-time information processing. Photorefractive crystals with short drift lengths (BaTiO3 and [...]) and long drift ones (Bi12SiO20 and semi-insulating GaAs) are particularly used in this thesis. In the first part, the photorefractive effect in electrooptic crystals is described in terms of Kukhtarev's band transport model. The explicit solution of the space-charge electric field for the case of one photorefractive species and one type of charge carrier is extended to the case of two photorefractive species and two types of charge carriers. The enhancement of the space-charge electric field is also described. In particular an approximate solution to Stepanov and Petrov's enhancement method of using AC external electric field is extended to a general case that describes the transient behavior for AC external electric field of arbitrary waveform. The anisotropic refractive index change due to the space-charge field formation is then described in terms of tensorial forms of the nonlinear susceptibility. In the second part, anisotropic beam coupling in photorefractive crystals is presented and a general set of coupled-wave equations that describes beam coupling in amplitude, phase, and polarization is derived by using the nonlinear and tensorial susceptibility. The polarization properties of the interacting waves are particularly stressed. Two limiting cases, i.e., one for scalar beam coupling and the other for cross-polarization beam coupling, are obtained from the general expression and solved. Experimental results of beam coupling in semi-insulating GaAs are presented, and the signs of dominant charge carriers and the density of photorefractive species are estimated from beam-coupling gain. The enhancement of beam-coupling gain and its temperature dependence are also discussed. In the third part, four-wave mixing for scalar and vector phase conjugation is described. Self-pumped phase-conjugate mirrors using photorefractive crystals are presented and one of the most interesting properties of these mirrors, i.e., the response to phase changes of inputs, is emphasized both theoretically and experimentally. In the fourth part, two-wave and four-wave mixing in photorefractive crystals are applied to moving object detection, mathematical operation on images, and one-way image transmission through phase-distorting media. In these applications, polarization properties of interacting waves are particularly utilized. In the fifth part, a novel method of vector phase conjugation by modal dispersal and scalar phase conjugation is discussed. The propagation characteristics of conjugate waves in strongly scattering media (e.g., mode-scrambling multimode fibers) are described theoretically, followed by the experimental demonstration of vector phase conjugation. In the theory the unitarity and time-reversal symmetry of the scattering matrix are incorporated into the analysis of the coherency matrix of the conjugate field. This theory which describes the physical process of the generation of vector phase conjugation can successfully explain the experimental results of its fidelity. In the last part, we describe experiments in which the new concept of modal dispersal of information and scalar phase conjugation is used for several novel applications that include nonreciprocal polarization-distortion correction, amplitude-distortion correction, and phase-conjugate multimode fiber-optic sensors. Experiments as well as proposals for these applications are presented.

Electromagnetic Environment Associated with Lightning Strikes to Tall Strike Objects

Calculation of electric and magnetic induced fields in humans subjected to electric power lines

Electro-optic and magneto-optic modulations of Goos-Hänchen effect in double graphene coating waveguide with sensing applications

Abstract. Rapid changes in the ionospheric current system give rise to induction currents in the conducting ground that can significantly contribute to magnetic and especially electric fields at the Earth's surface. Previous studies have concentrated on the surface fields, as they are important in, for example, interpreting magnetometer measurements or in the studies of the Earth's conductivity structure. In this paper we investigate the effects of induction fields at the ionospheric altitudes for several realistic ionospheric current models (Westward Travelling Surge, Ω-band, Giant Pulsation). Our main conclusions are: 1) The secondary electric field caused by the Earth's induction is relatively small at the ionospheric altitude, at most 0.4 mV/m or a few percent of the total electric field; 2) The primary induced field due to ionospheric self-induction is locally important, ~ a few mV/m, in some "hot spots", where the ionospheric conductivity is high and the total electric field is low. However, our approximate calculation only gives an upper estimate for the primary induced electric field; 3) The secondary magnetic field caused by the Earth's induction may significantly affect the magnetic measurements of low orbiting satellites. The secondary contribution from the Earth's currents is largest in the vertical component of the magnetic field, where it may be around 50% of the field caused by ionospheric currents. Keywords. Geomagnetism and paleomagnetism (geomagnetic induction) – Ionosphere (electric fields and currents)

Electric and magnetic fields (EMF) are ubiquitous. The earth has static electric fields, which produce lightning during thunderstorms, and geomagnetic fields created by electric currents within its core. Electric and magnetic fields are also produced during electric power generation, transmission, and use.Electric power has generally been considered safe during the more than 100 years of its use, although shocks and burns from direct contact with electrical conductors are a recognized health hazard. Of the approximately 1100 deaths from electric shock that occur each year in the United States, about three‐fourths result from unsafe operation of household appliances; accidents in the workplace account for the rest. The possible health consequences of electric and magnetic field exposure are a much more recent concern.Power‐frequency EMF exposure—unavoidable since the use of electricity has spread throughout the world—has been under investigation since the early 1970s. Investigations have included epidemiologic as well asin vitroandin vivolaboratory studies encompassing a wide range of diseases. The literature on EMF and health is vast, comprising over 1000 published studies, and has been reviewed in depth by several authoritative committees. Of note are reviews by the National Research Council of the National Academy of Sciences (NAS), the National Institute of Environmental Health Sciences (NIEHS) and the U.K. National Radiological Protection Board (NRPB).Electric power systems in the United States, Canada, and Mexico generate and transmit electricity as alternating current (ac), which oscillates at a frequency of 60 cycles per second, or 60 hertz (Hz). Most of the rest of the world generates power at 50Hz. Power‐frequency 50‐ and 60‐Hz fields occupy the extremely low‐frequency (ELF), nonionizing range of the electromagnetic spectrum. The ELF range includes frequencies from 3 to 3000Hz. Above 3000Hz are, in order of increasing frequency or decreasing wavelength, radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, x‐rays, and gamma rays. Microwaves have enough photon energy to heat tissue; ionizing radiation like x‐rays and gamma rays can damage biological systems by breaking chemical bonds. Extremely low‐frequency electric and magnetic fields can neither break bonds nor heat tissue, and the electric currents they induce in the body are very weak.Power‐frequency fields have very long wavelengths of about 5000km. Exposure distances are much shorter than this wavelength; under these circumstances, electric and magnetic fields are independent.Electric field strength increases with increasing voltage, or electric potential; magnetic field strength increases with increasing current. Both electric and magnetic fields decline rapidly with distance from their source, with a faster decline of fields from point sources such as machinery and a slower decline of fields from power lines. Electric fields are further reduced when shielded by conducting objects like buildings and have little penetrative ability; magnetic fields, on the other hand, are capable of penetrating tissue and are not easily shielded.Occupational exposure to electric and magnetic fields occurs from proximity to large motors as well as from wiring in buildings and the use of computers, office machines, and heating and air conditioning systems. Power transmission and distribution facilities are other sources.Accurate assessment of EMF exposure has presented many difficulties in epidemiologic studies and continues to be a considerable challenge. EMF have several unique characteristics that make them more difficult to measure than most other types of exposures. EMF are not readily detectable, are variable in time and space, and are to some extent present in all environments. Additionally, electric fields are both perturbed and intensified by conducting objects like the human body, so that fields measured at various points on the body's surface have different values. Because of the complexity of exposure circumstances, exposure reports from workers are not reliable.

Some functional fluids that respond to both magnetic and electric fields have been prepared and their characteristics are described. In this study, an electro-magnetorheological fluid (EMRF) dispersing zeolite particles containing metallic iron by reducing precipitated magnetite has been investigated. When the viscosity is measured by cone plate viscometer and cylindrical viscometer, electric and magnetic fields are applied both between cone and plate or two cylinders. In case of cone plate, the shear stress at constant shear rate increased with the increase of both magnetic field and electric field. On the other hand when the viscosity is measured by cylindrical viscometer, the shear stress at constant shear rate increased with the increase of electric field, however, the increase rate of shear stress by magnetic field is very small. In this case the magnetic field direction is perpendicular to electric field. The EMRF has typical characteristics to respond with magnetic and electric field. The shear stress of EMRF in electric field is stronger than that of magnetic field. Additionally, the inflection and peak point in the shear rate-shear stress curve are appeared and the behaviors of the clusters in the electric field are observed. The experimental results suggested that the fluid viscosity (shear stress/shear rate) is affected by the arrangement of clusters parallel or perpendicular to the direction of the EMRF flow.

Some functional fluids that respond to both magnetic and electric fields have been prepared and their characteristics are described. In this study, an electro-magnetorheological fluid (EMRF) dispersing zeolite particles containing metallic iron by reducing precipitated magnetite has been investigated. When the viscosity is measured by cone plate viscometer and cylindrical viscometer, electric and magnetic fields are applied both between cone and plate or two cylinders. In case of cone plate, the shear stress at constant shear rate increased with the increase of both magnetic field and electric field. On the other hand when the viscosity is measured by cylindrical viscometer, the shear stress at constant shear rate increased with the increase of electric field, however, the increase rate of shear stress by magnetic field is very small. In this case the magnetic field direction is perpendicular to electric field. The EMRF has typical characteristics to respond with magnetic and electric field. The shear stress of EMRF in electric field is stronger than that of magnetic field. Additionally, the inflection and peak point in the shear rate-shear stress curve are appeared and the behaviors of the clusters in the electric field are observed. The experimental results suggested that the fluid viscosity (shear stress/shear rate) is affected by the arrangement of clusters parallel or perpendicular to the direction of the EMRF flow.

In this paper, both electric field and magnetic field were used to assist the hot filament chemical vapor deposition (HFCVD) and we systematically investigated the effects of which on the (1) phase composition, (2) grain size, (3) thickness and (4) preferred orientation of diamond films through SEM, Raman and XRD. The application of magnetic field in electric field, so called ‘the magnetic and electric coupling fields’, enhanced the graphitization and refinement of diamond crystals, slowed down the decrease of film thickness along with the increase of bias current, and suppressed diamond (100) orientation. During the deposition process, the electric field provided additional energy to HFCVD system and generated large number of energetic particles which might annihilate at the substrate and lose kinetic energy, while the Lorentz force, provided by magnetic field, could constrict charged particles (including electrons) to do spiral movement, which prolonged their moving path and life, thus the system energy increased. With the graphitization of diamond films intensified, the preferred orientation of diamond films completely evolved from (110) to (100), until the orientation and diamond phase disappeared, which can be attributed to (I) the distribution and concentration ratio of carbon precursors (C2H2 and CH3) and (II) graphitization sequence of diamond crystal facets. Since the electron field emission property of carbon film is sensitive to the phase composition, thickness and preferred orientation, nano- carbon cones, prepared by the negative bias current of 20 mA and magnetic field strength of 80 Gauss, exhibited the lowest turn-on field of 6.1 V −1 μm−1.

The Martian bow shock represents the main interface between the upstream interplanetary space and the downstream planetary obstacle, where the solar-wind plasma and the frozen-in interplanetary magnetic field (IMF) begin to be perturbed. However, the physical characteristics of the Martian bow shock layer and the influence of the external solar wind drivers on them remain unclear. By employing a three-dimensional Hall magneto-hydrodynamic (MHD) model, this study aims to reveal the physical characteristics of the Martian bow-shock layer extracted from the maximum radially inward gradient of the solar-wind velocity (VS W), including the magnetic field, current density, electric fields, and the energy transfer between the fields and solar wind protons, as well as the influence of the VS W and the IMF on these features. Simulation results indicate that the IMF has initiated the processes of piling-up, draping, bending, and slipping at the Martian bow shock, inducing an associate current to flow from the +ZMS E pole to the −ZMS E pole along the bow-shock layer, with the strongest being located at the subsolar position. Furthermore, the total electric field at the Martian bow shock is constituted by the motional electric field (EM) with the +ZMS E direction around the ±ZMS E flanks and the outward ambipolar (EA) and Hall (EH) electric fields around the lower solar zenith angles; through these, the solar wind transfers its kinetic energy to the electromagnetic fields. A higher VS W gives rise to an enhanced magnetic field, current density, and electric fields at the Martian bow shock, thereby leading to an increase in the corresponding energy-transfer rates. A greater magnitude of the IMF cross-flow component tends to result in an intensified magnetic field, current densities, EM, and EH; while it causes a decreased EA and associated energy-transfer rate at the bow shock layer. If the Parker spiral angle of the IMF is not restricted to 90°, a portion of the quasi-parallel bow-shock layer will be formed, within which the magnitudes of the magnetic field, current density, EH, and the corresponding energy-transfer rate through EH are all lower than those of the quasi-perpendicular bow-shock layer. The results of this study provide valuable insights into the physical properties at the bow-shock layer that emerge during the Mars-solar-wind interactions.

Electromagnetic induction in the Earth’s interior is an important contributor to the near-Earth magnetic and electric fields. The oceans play a special role in this induction due to their relatively high conductivity which leads to large lateral variability in surface conductance. Electric currents that generate secondary fields are induced in the oceans by two different processes: (a) by time varying external magnetic fields, and (b) by the motion of the conducting ocean water through the Earth’s main magnetic field. Significant progress in accurate and detailed predictions of the electric and magnetic fields induced by these sources has been achieved during the last few years, via realistic three-dimensional (3-D) conductivity models of the oceans, crust and mantle along with realistic source models. In this review a summary is given of the results of recent 3-D modeling studies in which estimates are obtained for the magnetic and electric signals at both the ground and satellite altitudes induced by a variety of natural current sources. 3-D induction effects due to magnetospheric currents (magnetic storms), ionospheric currents (Sq, polar and equatorial electrojets), ocean tides, global ocean circulation and tsunami are considered. These modeling studies demonstrate that the 3-D induction (ocean) effect and motionally-induced signals from the oceans contribute significantly (in the range from a few to tens nanotesla) to the near-Earth magnetic field. A 3-D numerical solution based on an integral equation approach is shown to predict these induction effects with the accuracy and spatial detail required to explain observations both on the ground and at satellite altitudes.

This study aims to clarify the frequency characteristics of the spatial distribution of electromagnetic noise inside a distance of 3 m around a printed circuit board (PCB) by simulation and experiment. It is also shows that the finite difference time domain method (FDTD method) is a useful tool to estimate the frequency characteristic of the spatial distribution for the electric and magnetic field around the PCB. By comparison between the electric and magnetic near field spectrum above the printed line by simulation, these spectra are shown to have differences in the resonance frequency: when the characteristics of the electric and magnetic field strength at 60 ns after the excitation is calculated, the electric field is decreased, the magnetic field is not decreased, as the distance from PCB is farther. From the characteristics of particular frequencies, the electric field spectrum at 3 MHz, i.e, clock pulse, is decreased, whereas the magnetic field is not decreased. The electric and magnetic field strength at the resonance frequency, 417 MHz, is decreased in inverse proportional to the square of the distance. It is also clear that the low frequency magnetic field strength may be superior to higher frequency.

Overview Having shown in Chapter 5 that the magnetic force must exist, we will now study the various properties of the magnetic field and show how it can be calculated for an arbitrary (steady) current distribution. The Lorentz force gives the total force on a charged particle as F = q E + q v × B . The results from the previous chapter give us the form of the magnetic field due to a long straight wire. This form leads to Ampere’s law , which relates the line integral of the magnetic field to the current enclosed by the integration loop. It turns out that Ampere’s law holds for a wire of any shape. When supplemented with a term involving changing electric fields, this law becomes one of Maxwell’s equations (as we will see in Chapter 9). The sources of magnetic fields are currents, in contrast with the sources of electric fields, which are charges; there are no isolated magnetic charges, or monopoles . This statement is another of Maxwell’s equations. As in the electric case, the magnetic field can be obtained from a potential, but it is now a vector potential ; its curl gives the magnetic field. The Biot–Savart law allows us to calculate (in principle) the magnetic field due to any steady current distribution. One distribution that comes up often is that of a solenoid (a coil of wire), whose field is (essentially) constant inside and zero outside. This field is consistent with an Ampere’s-law calculation of the discontinuity of B across a sheet of current. By considering various special cases, we derive the Lorentz transformations of the electric and magnetic fields. The electric (or magnetic) field in one frame depends on both the electric and magnetic fields in another frame. The Hall effect arises from the q v × B part of the Lorentz force. This effect allows us, for the first time, to determine the sign of the charge carriers in a current.