Showing papers on "Electric field published in 1980"

Electric dyadic Green's functions in the source region

Abstract: A straightforward approach that does not involve delta-function techniques is used to rigorously derive a generalized electric dyadic Green's function which defines uniquely the electric field inside as well as outside the source region. The electric dyadic Green's function, unlike the magnetic Green's function and the impulse functions of linear circuit theory, requires the specification of two dyadics: the conventional dyadic G- e outside its singularity and a source dyadic L-which is determined solely from the geometry of the "principal volume" chosen to exclude the singularity of G- e . The source dyadic L-is characterized mathematically, interpreted physically as a generalized depolarizing dyadic, and evaluated for a number of principal volumes (self-cells) which are commonly used in numerical integration or solution schemes. Discrepancies at the source point among electric dyadic Green's functions derived by a number of authors are shown to be explainable and reconcilable merely through the proper choice of the principal volume. Moreover, the ordinary delta-function method, which by itself is shown to be inadequate to extract uniquely the proper electric dyadic Green's function in the source region, can be supplemented by a simple procedure to yield unambiguously the correct Green's function representation and associated fields.

Satellite measurements and theories of low altitude auroral particle acceleration

Abstract: Several previous and new S3-3 satellite results on DC electric fields, field-aligned currents, and waves are described, interpreted theoretically, and applied to the understanding of auroral particle acceleration at altitudes below 8000 km. These results include the existence of two spatial scale sizes (less than 0.1 degree and a few degrees invariant latitude) in both the perpendicular and parallel electric fields; the predominance of S-shaped rather than V-shaped equipotential contours on both spatial saales; the correlated presence of field-aligned currents, low frequency wave turbulence, coherent ion cyclotron wave emissions and accelerated upmoving ions and downgoing electrons; intense waves inside electrostatic shocks and important wave-particle interactions therein; correlations of field-aligned currents with magnetospheric boundaries that are determined by convection electric field measurements; electron acceleration producing discrete auroral arcs in the smaller scale fields and producing inverted-V events in the larger scale fields; ion and electron acceleration due to both wave-particle interactions and the parallel electric fields. Further analyses of acceleration mechanisms and energetics are presented.

Photorefractive effects and light‐induced charge migration in barium titanate

Abstract: We propose a new theoretical model for the light‐induced migration of charges which mediates the ’’photorefractive effect’’ (light‐induced refractive index change) in barium titanate and other crystals. We also present experimental results of various effects of this light‐induced charge migration in a single‐domain crystal of barium titanate, specifically, (1) energy transfer between two intersecting optical beams, (2) optical four‐wave mixing and optical‐beam phase conjugation, (3) erasure of spatial patterns of photorefractive index variations, and (4) photoconductivity. The theoretical model predicts the observed dependences of these effects on (1) beam intensities, directions, and polarizations, (2) crystal orientation, and (3) on an externally applied dc electric field. Time dependences of transients as well as steady‐state magnitudes are predicted. In this model, identical charges migrate by hopping between adjacent sites, with a hopping rate proportional to the total light intensity at the starting site. The net hopping rate varies with the local electric potential that is calculated self‐consistently from the charge migration pattern. In barium titanate the charges are positive with a density of (1.90.2) ×1016 cm−3 at 514 nm. The origin of the charges and sites is at present unknown. The hopping rate constant determined from optical beam interactions is used to predict the observed photoconductivity of 1.3×10−10 cm Ω−1 W−1 at 514 nm.

Creating an asymmetric plasma resistivity with waves

Abstract: Preferential heating of electrons traveling in one direction can support a current even in the absence of a dc electric field. An immediate implication is that even waves which carry little toriodal momentum, such as electron cyclotron waves, may be attractive as a means for generating steady-state toroidal current in a tokamak. An analytical expression is derived for the current generated per power dissipated, which agrees remarkably well with numerical calculations.

Generation of large-scale regions of auroral currents, electric potentials, and precipitation by the divergence of the convection electric field

Abstract: It is shown that discontinuities in the magnetospheric convection electric field E with ▽ · E <0 can generate large-scale regions (of the order of 100 km in width) of magnetic field-aligned currents with associated field-aligned electric potential differences and electron precipitation of the magnitudes and widths observed in auroral regions. Such an electric field discontinuity is known to exist along the evening boundary between sunward and antisunward convection. In addition, such discontinuities may also exist over the polar cap, on account of inhomogeneities in the magnetosheath flow and in regions, such as the Alfven layer, where drifting trapped particles charge separate. The present analysis assumes that the field-aligned current is governed by the free particle motion in dc electric and magnetic fields, and nothing is assumed to inhibit this free particle motion.

Electrostrictive effect in lead magnesium niobate single crystals

Abstract: Transverse and longitudinal elastic strain have been measured for electric fields applied along the 〈100〉 direction in single crystals of lead magnesium niobate [Pb(Mg1/3Nb2/3)03], using a bonded strain gauge technique. A quadratic electrostrictive relation holds between induced elastic strain and electric polarization for temperatures near the low‐frequency dielectric maximum. The electrostriction coefficients are almost temperature independent with values Q11=2.50×10−2 m4/C2 and Q12=−0.96×10−2 m4/C2. To check the direct measurements, the hydrostatic Q coefficient was determined independently by measuring the pressure dependence of the dielectric permittivity. The value Qh =0.60×10−2 m4/C2 obtained is in good agreement with that calculated from the direct measurements.

Physics: Principles with Applications

Abstract: Describing motion - kinematics in one dimension kinematics in two or three dimensions - vectors motion and force - dynamics circular motion - gravitation work and energy linear momentum rotational motion bodies in equilibrium - elasticity and fracture fluids vibrations and waves sound temperature and kinetic theory heat the first and second laws of thermodynamics electric charge and electric field electric potential and electric energy electric currents DC circuits, electromagnetic induction and Faraday's Law - AC circuits electromagnetic waves light - geometric optics the wave nature of light optical instruments special theory of relativity early quantum theory and models of the atom quantum mechanics of atoms molecules and solids nuclear physics and radioactivity nuclear energy effects and uses of radiation elementary particles astrophysics and cosmology. Appendices.

Guiding center drift equations

Abstract: The equations for particle drift orbits are given in a new magnetic coordinate system. This form of the equations separates the fast motion along the magnetic field lines from the slow motion across the lines. In addition, less information is required about the magnetic field structure than in alternative forms of the drift equations.

Io's interaction with the plasma torus

Abstract: A new model for the interaction of Io with the dense corotating plasma of the Io torus is described which involves pickup and Alfven waves carrying a field-aligned current. Pickup refers to the process whereby ions freshly created near Io are accelerated by the corotational electric field. It is shown that the pickup current is connected to a field-aligned current carried by an Alfven wave. The combination of currents allows for a self-consistent determination of the electric field in Io's vicinity. Using a simplified solution for the electric field, we calculate the total pickup rate, field-aligned current, enhancement of plasma density in Io's vicinity, thermal energy injected into the torus, UV radiation power, and inertial drag on the magnetosphere. All observations made by Voyager are compatible with an electron impact ionization mechanism and a neutral SO/sub 2/ Io atmosphere with a density of 10/sup 9/ cm/sup -3/.

Hysteresis phenomena in polyvinylidene fluoride under high electric field

Abstract: Dielectric and piezoelectric responses caused by a high electric field and a 10‐Hz small strain have been simultaneously measured for stretched polyvinylidene fluoride using a minicomputer system. The electric field was applied up to 240 MV/m in a sinusoidal or triangular wave form in the frequency range 10−4–10−2 Hz at temperatures between −100 and 100 °C. Ferroelectric hysteresis loops were observed even below the glass‐transition temperature of −60 °C. At 20 °C the 120‐MV/m electric field gave the remanent polarization Pr of 50 mC/m2 which resulted in the piezoelectric activities e31 and e32 of 70 and 7.5 mC/m2, respectively. The origin of Pr was confirmed to be the molecular dipole orientation because the value of Pr was independent of the frequency of applied field. The coercive field Ec significantly decreased with increasing temperature from 180 MV/m (−100 °C) to 25 MV/m (100 °C), while Pr showed only a slight temperature dependence.

Charged macromolecules in external fields. I. The sphere

Abstract: The response of rigid macroions in aqueous solution to an external electric field is considered. The external field, which may be steady or oscillating, induces perturbations in the distribution of coions and counterions, and also in the electrical and solvent velocity fields. The basic equations that describe the various fields are reviewed, and then specialized to the special problem of thin double layers. Boundary conditions are derived which differ from those used in previous work. Previous treatments of the counterion flux into the double layer have either omitted the flux, or taken it to be in phase with the applied field. We find that this flux is large, and has a significant component out of phase. The new boundary conditions make substantial changes in the complex dielectric response. The dominant slow process that controls relaxation is the slow diffusion of neutral salt in the environment of the macromolecule. Large perturbations are induced in the neutral salt concentration by charge distortio...

Ion heating by strong electrostatic ion cyclotron turbulence

Abstract: A theory of the ion heating due to electrostatic ion cyclotron (EIC) waves in the auroral zone is presented. Due to the slowly convecting nature of the EIC mode, quasi-linear plateau formation cannot stabilize the waves, and growth occurs until the nonlinear mechanisms of ion resonance broadening and electron trapping provide saturation. The large amplitude and coherent nature of the resulting wave imply that quasi-linear theory provides only a lower limit to the ion heating. An upper bound on the heating rate is derived using a time-average model of ion dynamics in the coherent waves. The effects of ion heating in the presence of the magnetic gradient force and parallel electric fields are considered, with the result that perpendicular energies over 100 eV are easily attainable from a 1 eV source plasma. Perpendicular heating in the absence of a parallel electric field yields conical ion distributions, which in the presence of an electric field become field-aligned beams.

Sources of the strongest RF radiation from lightning

Abstract: Experiments performed at the Kennedy Space Center, Florida during TRIP-78 identified sources of the strongest RF radiation from lightning in the HF-VHF frequency range. Measurements were made of electric field changes associated with RF radiation using a field change system triggered on the output of an RF detector. The field changes associated with the strongest RF radiation are very fast (10 - 20 microseconds), bipolar pulses having an initial negative going half-cycle followed by a positive overshoot. These fast pulses consistently produced more RF radiation than was associated with return strokes, and their shape was remarkably consistent, independent of frequency.

Finite elements in electrical and magnetic field problems

Abstract: whilst both the electrical and mechanical activity of the heart is modelled in the following chapter. The dynamics of blood glucose and its regulating hormones is developed into a new model, building on the many previous attempts in this area. As a contrast, the electrical rythms of the gastro-intestinal tract, which have received little attention to date, are dealt with in chapter six. The lungs, and mechanical properties of the respiratory system, have frequently been modelled, but in this section both mathematical and electronic descriptions are evolved which incorporate adaptive trackers, and results are presented from clinical applications of the techniques. Serious consideration is given to modelling circadian and related biological rhythms, with many of the proposed interconnected oscillator systems discussed, and finally a chapter is devoted to the concept of catastrophe theory applied to psychological modelling, with a detailed analysis of anorexia nervosa, the obsessive fasting by slimmers. Those interested in modelling biological systems will find this book very useful, since the references to each chapter are very thorough: however, the problems with the vast complexity of the human body, and the engineering problems of obtaining measurements, ensure that this is a field just opening up for research. PETER WATTS, Medical Engineering Unit, UMIST.

Electromagnetic scattering by surfaces of arbitrary shape

Abstract: The electric field integral equation (EFIE) is used with the moment method to develop a simple and efficient numerical procedure for treating problems of scattering by arbitrarily shaped objects. For numerical purposes, the objects are modeled using planar triangular surfaces patches. Because the EFIE formulation is used, the procedure is applicable to both open and closed surfaces. Crucial to the numerical formulation is the development of a set of special subdomain-type basis functions which are defined on pairs of adjacent triangular patches and yield a current representation free of line or point charges at subdomain boundaries. The method is applied to the scattering problems of a plane wave illuminated flat square plate, bent square plate, circular disk, and sphere. Excellent correspondence between the surface current computed via the present method and that obtained via earlier approaches or exact formulations is demonstrated in each case.

Computer studies of the dynamic evolution of the geomagnetic tail

Abstract: The dynamic evolution of a stretched magnetotail configuration is investigated numerically by means of a two-dimensional time-dependant nonlinear resistive MHD code. The initial configuration is shown to be stable in ideal MHD. The unstable evolution is initiated by imposing a finite resistivity. Rather independently of the boundary conditions, the following phenomena develop spontaneously: plasma sheet thinning, topological changes of the magnetic field configuration, the formation of neutral lines with an almost stationary X line, large induced cross-tail electric fields, conversion of magnetic to kinetic energy resulting in strong earthward and tailward flow close to the neutral sheet, and outside the neutral sheet a significant part of the flow parallel to the magnetic field. This flow reverses sign across the plasma sheet boundary tailward of the X line. The results support the tearing theory of magnetospheric substorms. At the later stages the configuration around the X line is similar to that obtained from steady state reconnection theory; in particular we found that two current layers form downstream of the magnetic field separatrix, which may represent structures developing into slow shock waves.

Electron transport properties in GaAs at high electric fields

Abstract: Electron distribution function, drift velocity, mean energy, valley population fractions and diffusion coefficient were calculated at high, up to 100 kV/cm, electric fields. Calculations were carried out by the Monte Carlo method. The three-valley model of GaAs conduction band was used. The obtained results were compared with the experimental data.

Post-Ionization of Field-Evaporated Ions

Abstract: It is shown that the final observed charge state of a field-evaporated ion can be explained by the occurrence of post-ionization whereby an ion being accelerated away from a metal surface in a strong electric field loses one or more electrons by tunneling into the substrate. Calculations using an approximate analytic formula derived from a simple model potential predict the probability of post-ionization for many different elements.

Counterstreaming electron beams at altitudes of ∼1 RE over the auroral zone

Abstract: Intense beams of electrons with energies in the keV range have been streaming simultaneously both parallel and antiparallel to the magnetic field direction at altitudes between 4000 and 8000 km at auroral latitudes. The peak flux observed was 3 x 10/sup 11/ (cm/sup 2/ s sr keV)/sup -1/ at an energy of 160 eV. The beams are often tightly collimated with widths in pitch angle as narrow as approx.1 /sup 0/. Analysis of the energy spectrums of the beams and the simultaneously observed loss cones in the trapped electron population shows that the energization of the beams cannot be understood as acceleration by a simple quasi-static parallel electric field. Alternative models include acceleration by wave-particle interactions or by fluctuating electric fields. One candidate model consistent with the observations is outlined in which the energetic electrons in the counterstreaming electron beams are accelerated from the ambient cold plasma by multiple flickering double layers located in the 1-R/sub E/ altitude range.

Effects of high-latitude conductivity on observed convection electric fields and Birkeland currents

Abstract: Relationships between convective electric fields, Birkeland currents, and ionospheric conductivity at high latitudes are investigated by using simultaneous measurements of electric and magnetic fields and electron fluxes from the S3-2 satellite. Cases in which the polar cap is in sunlight and darkness are studied to assess the importance of ionospheric conductivity. We find that when the ionospheric conductivity is high, as it normally is in the auroral zones and the sunlit polar cap, Birkeland current sheets exist that deflect the magnetic field approximately in the direction of the convection, typically antisunward in the polar caps and sunward in the auroral zones. Under winter conditions (a dark polar ionosphere), no large-scale antisunward deflection of magnetic field lines is found in the polar cap. Magnetic field deflections in the auroral zone are the result of the region 1/region 2 current systems discussed by Iijima and Potemra (1976). In the cases studied, region 1 currents are not observed to extend significantly poleward of the electric field reversal. We interpret this result as indicating the existence of strong conductivity gradients near the poleward boundary of the auroral oval, even in sunlight conditions. Deflections of magnetic field lines in the summer polar cap, first reported by McDiarmid et al. (1978), result from currents which serve to link the high-latitude generator to the polar ionospheric load. Two types of linkage appear in the data; (1) Region 1 currents are greater than region 2 currents, with the excess region 1 current flowing across the polar cap from dawn to dusk. (2) An extra set of field-aligned currents exist which are clearly detached from those of region 1 and are entirely poleward of the convective electric field reversal. We find that the evidence for antisunward convection on closed field lines threading the boundary layer, cited by McDiarmid et al. (1978), is inconclusive. With our more complete data set there is some evidence at ionospheric altitudes for a boundary layer, but in such cases there is only a modest (a few kilovolts) potential drop across the layer and there are insignificant Birkeland currents.

Method and apparatus for controlling the electric charge on droplets and ink-jet recorder incorporating the same

Abstract: Method and apparatus for controlling the electric charge on droplets formed by the breaking up of a pressurized liquid stream at a drop formation point located within an electric field The field is provided to have an electric potential gradient and means are provided to effect drop formation at a point in the field corresponding to the desired predetermined charge to be placed on the droplets at the point of their formation The location of the drop formation point within the charging field may be controlled by one or more signals applied to various components of the apparatus The method and apparatus are particularly suited to ink-jet recording systems

Static dielectric properties of stockmayer fluids

Abstract: Dielectric constants for the Stockmayer fluid are computed both from the equilibrium fluctuations of the polarization and from the polarization response to an applied field in a molecular dynamics simulation with periodic boundary conditions and with the dipole interactions treated by the Ewald method. The dielectric constant at finite wavelength is obtained from a Kirkwood-like expression, while for uniform polarization fluctuations a different expression applies due to the absence of surface effects in the Ewald calculation. The results are nearly independent of the number (up to 500) of particles investigated, even at large values of the dipole moment. The dielectric constants obtained from the approximate solution of the hypernetted chain integral equation are considerably larger than the molecular dynamics results except at low dielectric constants. The external field simulation permits study of the non-linear dependence of the dielectric constant on the magnitude of the applied electric field.

Liquid‐crystal orientational bistability and nematic storage effects

Abstract: A new class of nematic liquid‐crystal storage effects with potential display applications is described. We have developed structures, produced by special surface alignment patterns, exhibiting bistable configurations. Switching between states has been demonstrated with both electric and magnetic fields. The movement of disclinations and the topological distinction between states play essential roles in bistable switching. The properties of the bistable states and a proposed switching mechanism are described.

Dielectric Breakdown of Cell Membranes

Abstract: A Coulter Counter is a measuring device for counting and sizing non-conducting particles suspended in a conducting medium. This instrument is based on the principle that the electrical resistance in a small orifice, across which a voltage is applied, will change when a suspension of non-conducting particles is sucked through it. The current or voltage pulses arising are, to a first approximation, proportional to the size of the particles (size = shape factor X volume); this means that after linear electronic amplification and subsequent pulse height analysis the size distribution of each population under investigation can be obtained. Using conventional Coulter Counters, however, the measured size distribution is generally strongly distorted (skewed) due to inhomogeneities in the electric field strength in and near of the orifice; the pulse height becomes dependent on the path and orientation of each particle in the orifice (GROVER et al., 1969a, b, 1972; THOM, 1972). As described previously (ZIMMERMANN et al., 1973) the distortion arising from the inhomogeneous field can be eliminated by hydrodynamic focusing of the suspension flow. Then the particles travel on the same pathway, parallelly oriented, along the central axis through the orifice, and a true measurement of the real size distribution of the population can be obtained.

Relationship between trapped holes and interface states in MOS capacitors

Abstract: Metal–silicon‐dioxide–silicon capacitors with dry‐grown oxides, when stressed at fields of 7.1–7.5 MV/cm with field plate positive at 90 K, showed buildup of trapped holes. Interface states appeared only after the samples were warmed. The number of interface states generated in one hour at either 20 or 66 °C was linearly proportional to the number of trapped holes, and the number of states generated in the central 0.7‐eV portion of the Si bandgap during one year’s storage at room temperature was essentially equal to the original number of trapped holes. These results provide quantitative evidence of a cause and effect relationship between trapped holes and interface states in the Si‐SiO2 system.

Impact ionization rates for electrons and holes in Ga0.47In0.53As

Abstract: We report the determination of the impact ionization rates for holes and electrons in Ga0.47In0.53As with the electric field oriented in the 〈100〉 direction. Our measurements show that the ionization rate for electrons α is greater than that for holes (β) by about a factor of 2 over electric fields ranging from 2.0×105 to 2.5×105 V cm−1 at 295 K.

Waves and transport in the pure electron plasma

Abstract: Investigations of low frequency waves and transport in a plasma consisting almost purely of electrons are presented here. This plasma is trapped in a cylindrical system with radial confinement supplied by a strong axial magnetic field and axial confinement supplied by electrostatic fields. Very long containment times are possible. Classical transport due to electron‐neutral collisions has been investigated and good agreement with the theory of Douglas and O’Neil is obtained. Externally launched diocotron waves are investigated. The modal frequencies agree well with linear theory, but the damping is governed by nonlinear effects. Experimental scaling laws for the damping rates are given. Measurements of spatial transport due to these modes are also presented. A signature of this process is that the transport is strongly localized spatially.

Comparison of the coupling of grounded humans, swine and rats to vertical, 60-Hz electric fields.

Abstract: Published and new data for grounded humans, swine, and rats exposed to vertical, 60-Hz electric fields are used to determine field strengths at the surfaces of the bodies and average components of induced-current density along the axes of the bodies At the tops of the bodies, surface electric fields are increased (enhanced) over the unperturbed field strength present before the subjects entered the field by factors of 17,7, and 4 for humans, swine, and rats, respectively For an unperturbed field strength of 10 kV/m, average induced axial current densities in the neck, chest, abdomen, and feet are: 550, 190, 250, and 2000 nA/cm2, respectively, for humans; 40, 13, 20, and 1100 nA/cm2, respectively, for swine; and 28, 16, 2, and 1400 nA/cm2, respectively, for rats These data are used to show that the actual electric fields experienced by animals depend strongly on the shape of the body and its orientation relative to the electric field and ground plane This fact must be taken into account if biological data obtained with laboratory animals are to be used for the assessment of possible hazards to humans exposed to 60-Hz electric fields