Showing papers on "Electric field published in 1978"
Book•
01 Jan 1978
974 citations
TL;DR: In this article, it was shown that the electrical conductivity of carbon polyvinylchloride composites can be attributed to a novel mechanism of tunneling with potential-barrier modulation by thermal fluctuations.
Abstract: We present evidence that in carbon-polyvinylchloride composites, consisting of aggregates of carbon spheres (100-400 \AA{}) dispersed in the insulating matrix, the electrical conductivity can be ascribed to a novel mechanism of tunneling with potential-barrier modulation by thermal fluctuations. Theoretical consideration of the tunneling-probability modification by thermal fluctuating electric field across tunnel junctions yields expressions for the temperature and the field dependences of the conductivity in excellent accord with experimental results.
548 citations
TL;DR: The antipolar crystal form of poly(vinylidene fluoride) can be made piezoelectric and pyroelecric by the temporary application of electric fields in excess of 1 MV/cm at room temperature as discussed by the authors.
Abstract: The antipolar crystal form of poly(vinylidene fluoride) can be made piezoelectric and pyroelecric by the temporary application of electric fields in excess of 1 MV/cm at room temperature. Infrared and x‐ray diffraction data reveal that the polarization occurs in two stages. At fields near 1 MV/cm, a phase transition to a polar form II occurs with presumably no change in chain conformation. Fields near 5 MV/cm cause a change in conformation to produce form I. Our results indicate that at least a portion of the residual polarization occurs within the crystal phase of the polymer.
533 citations
TL;DR: In this paper, the variation of the selfconsistent electrostatic potential along the magnetic field is calculated by application of the principle of quasi-neutrality to the plasma components distributed along an auroral field line.
Abstract: The variation of the self-consistent electrostatic potential along the magnetic field is calculated by application of the principle of quasi-neutrality to the plasma components distributed along an auroral field line. The equilibrium plasma consists of hot anisotropic magnetospheric plasma, ionospheric plasma evaporated or extracted upward by the parallel electrostatic field, and backscattered electrons. It is shown that the above charged particle populations can support a potential difference of up to several Kilovolts between the equator and the ionosphere along an auroral field line. Moreover, the corresponding parallel electric field has the proper signature to account for electron precipitation characteristics. Comparisons between theoretical and observed electron precipitation fluxes lead to estimates for the various physical parameters in the model.
385 citations
TL;DR: In this article, a review of the main results on electrostatic double layers obtained from theory and laboratory and space experiments up to the spring of 1977 is given, among other things, necessary criteria for existence and stability, quantitative estimates of charge separation and thickness, and some probable cause of DL-formation in terms of an instability.
Abstract: A review is given of the main results on electrostatic double layers (sometimes called ‘space charge layers’ or ‘sheaths’) obtained from theory and laboratory and space experiments up to the spring of 1977. The paper begins with a definition of double layers in terms of potential drop, electric field, and charge separation. Then a review is made of the theoretical results obtained so far. This covers, among other things, necessary criteria for existence and stability, quantitative estimates of charge separation and thickness, and some probable cause of DL-formation in terms of an instability. Next, experimental results obtained in the laboratory are compared with the theoretical results. Due to recent progress in experimental technique, the interior of a double layer can now be studied in much more detail than was possible before. By means of barium jets and satellite probes, double layers have now been found at the altitudes that were previously predicted theoretically. The general potential distribution above the auroral zone, suggested by inverted V-events and electric field reversals, is corroborated.
315 citations
TL;DR: In this paper, the time-dependent Smoluchowski equation with a Coulomb potential is solved analytically for a general boundary condition, and expressions for the distribution function, reaction rate, and survival probability are given.
Abstract: The time‐dependent Smoluchowski equation with a Coulomb potential is solved analytically for a general boundary condition, and expressions for the distribution function, reaction rate, and survival probability are given. The expressions are evaluated numerically and the long‐time behavior is derived. The theoretical results apply to experiments involving ion recombination without an electric field (or where there is a time delay in the application of the field), to scavenging experiments, and to fluorescence quenching.
314 citations
TL;DR: In this article, the classical theory of scattering under the Coulomb potential of both charged and neutral particles is used to derive formulae for the energy deposition rate and mean scattering of a beam of charged particles interacting with a cold hydrogen target of arbitrary ionization level as a function of the column density traversed by the beam.
Abstract: The classical theory of scattering under the Coulomb potential of both charged and neutral particles is used to derive formulae for the energy deposition rate and mean scattering of a beam of charged particles interacting with a cold hydrogen target of arbitrary ionization level as a function of the column density traversed by the beam. These general results hold for any form of stable injection energy spectrum, and their relevance to the existing literature on chromospheric heating during solar flares is discussed.
311 citations
01 Apr 1978
294 citations
TL;DR: In this article, a model for the field-aligned propagation of transverse electric fields and associated fieldaligned sheet currents is presented which takes into account the wave nature of the process.
Abstract: A model for the field-aligned propagation of transverse electric fields and associated field-aligned sheet currents is presented which takes into account the wave nature of the process. The model is applied to the separate cases of ionospheric and magnetospheric sources, and the resulting ionospheric electric field to field-aligned sheet current ratios are determined for comparison with experimental observations. It is found that the magnetospheric wave 'conductivity' for shear mode Alfven waves is small with respect to typical values of the height-integrated ionospheric Pedersen conductivity. For plasma convecting across a stationary disturbance a dynamic equilibrium is achieved in which field-aligned currents flow continuously away from the source on convecting field lines. Consistency with typical ionospheric electric fields requires that the field-aligned sheet currents are limited to around 0.1 A/m for ionospheric polarization sources, while magnetospheric sources are easily capable of 1 A/m or more.
272 citations
TL;DR: In this paper, the authors extended the DV-Xα cluster method to ionic crystals with inclusion of the long-ranged Coulomb potential of the ions outside the cluster, and the surface and the bulk electronic structures of MgO crystal were calculated.
Abstract: Discrete variational (DV) Xα cluster method is extended to ionic crystals with inclusion of the long-ranged Coulomb potential of the ions outside the cluster. As a typical example of partially ionic crystals, the surface and the bulk electronic structures of MgO crystal are calculated. The strong electric field, the reduction in the Madelung potential and the charge redistribution on the surface are found to be important factors for the formation of the surface state. Various features of the DV-Xα cluster method, such as the size and the shape dependence of the cluster, the effect of the exterior potential and so on are investigated.
226 citations
TL;DR: In this article, dissipative test electromagnetic fields in a black-hole background were studied and they were shown to satisfy Ohm's law with a surface resistivity of $4.377$ ohms.
Abstract: We study dissipative test electromagnetic fields in a black-hole background. Quantities such as surface velocity, tangential electric field, normal magnetic induction, total surface current, and conduction surface current are introduced and are shown to satisfy Ohm's law with a surface resistivity of $4\ensuremath{\pi}\ensuremath{\simeq}377$ ohms. Associated with these currents there exists a "Joule heating". These currents can exist when the black hole is inserted in an external electric circuit, but they can exist even in the absence of external currents. In particular, we study the eddy currents induced by the rotation of a black hole in an oblique uniform magnetic field, and we show how the computation of the ohmic losses allows a very simple derivation of the torque exerted on the hole.
TL;DR: In this article, the authors investigated the nonlinear development of the feedback instability for a conjugate perturbation elongating in the east-west direction, having a width of several tens of kilometers at the ionospheric level, standing along the magnetic field line.
Abstract: Being fed by the large-scale magnetospheric convection, the coupled ionosphere-magnetosphere system is subject to a feedback instability for a conjugate perturbation elongating in the east-west direction, having a width of several tens of kilometers at the ionospheric level, standing along the magnetic field line. The growth time is as short as several minutes even when no hot electrons are involved in the field-aligned current. Nonlinear development of the feedback instability is numerically investigated, taking hot electrons into account. The following conclusions are obtained. (1) An auroral arc can develop within a few tens of seconds once hot electrons take part. (2) The induced potential associated with the arc can reach several hundred volts. This predicts that the upward field-aligned current may be provided by electrons with energies of the order of several hundred electron volts, provided anomalous resistivity or double layers develop. (3) The electron density enhancement is directly connected with the upward field-aligned current and hence the auroral arc. (4) The downward current is localized equatorward of the upward current, when the background electric field is westward. (5) The electrojet current can grow to a few thousand amperes, which can either be westward or eastward, depending on the direction of the electric field. (6) The induced electric field inside the arc is almost constant and different from outside. These results are consistent with the observational results.
TL;DR: In this article, a simple analytic quasi-static electric potential field was used to simulate the magnetospheric convection field at ionospheric heights, and the transition region within the auroral zone where the meridional electric field component reverses was brought into close agreement with Heppner's (1977) observations.
Abstract: The observed magnetospheric convection field at ionospheric heights is simulated by a simple analytic quasi-static electric potential field. In particular, the transition region within the auroral zone where the meridional electric field component reverses is brought into close agreement with Heppner's (1977) observations. The location of zero meridional electric field strength in the model is compared with the observed Harang discontinuity (Maynard, 1974), where the zonal plasma flow reverses. The field-aligned electric currents associated with the model electric field occur within two regions. In region 1, within the auroral zone, maximum outflow out of the ionosphere occurs at 1600 LT. In region 2, equatorward of the auroral zone, maximum outflow is near 0700 LT, consistent with measurements of Iijima and Potemra (1976).
TL;DR: In this paper, a theoretical analysis has been conducted based on the model that positive ions produced by ionization near the wire electrode move toward the plate, introducing the bulk convective motion of neutral molecules as the result of collisions of ions and neutral molecules.
Abstract: The corona wind, with a velocity of several meters per second, is caused by applying high electric tension to bring about corona discharge in gases. In this paper the corona wind is experimentally and theoretically analyzed from an electrohydrod ynamical (EHD) standpoint. Experiments have been performed mainly in nitrogen by a two-dimensional electrode arrangement of a fine wire anode and a plate cathode. The voltage-current characteristics of an electrostatic probe indicate that positive ions predominate in the whole space except in an extremely narrow region close to the wire. A theoretical analysis has been conducted based on the model that positive ions produced by ionization near the wire electrode move toward the plate, introducing the bulk convective motion of neutral molecules as the result of collisions of ions and neutral molecules. The electric potential distribution in the space and pressure distribution on the plate calculated numerically agree well with the experimental data. Consequently, it is made clear that the corona wind is caused by the Coulomb force exerted on ions and collisions of ions and neutral molecules of gas.
TL;DR: In this paper, the ionospheric electric fields and currents that distribute globally were calculated using a fairly realistic empirical ionosphere conductivity model and the field-aligned current distribution inferred from TRIAD measurements, showing that the fieldaligned currents observed during disturbed periods can account for the equatorial fluctuations and reversals in electric field and associated magnetic disturbances noted during such times.
Abstract: Observational evidence indicates that high-latitude magnetic activity can be causally related to fluctuations and reversals of the equatorial electric field. Using Birkeland currents as the driving forces, we have made numerical calculations of the ionospheric electric fields and currents that distribute globally. Our calculations utilize a fairly realistic empirical ionospheric conductivity model and the field-aligned current distribution inferred from TRIAD measurements. The results presented here demonstrate that the field-aligned currents observed during disturbed periods can account for the equatorial fluctuations and reversals in electric field and associated magnetic disturbances noted during such times. In this way, magnetospheric dynamics has a direct and significant influence on the equatorial ionosphere through the ionospheric conductivity.
TL;DR: The results establish transient electric dichroism measurements as a technique well suited for study of alterations in the length and base pair inclination of rod-like DNA molecules.
Abstract: We report transient electric dichroism studies on monodisperse rod-like DNA molecules. By using restriction fragments and DNAs of known length, it is shown that the orientation time is accurately predicted by the theoretically calculated rotational diffusion coefficient. The field dependence of the steady-state dichroism values is not consistent with the induced electric dipole orientation mechanism, and the time dependence is not consistent with the presence of a permanent dipole moment. In order to explain the dependence of the dichroism on the electric field, the ionic strength of the medium, and the length of the macromolecule, we propose a new model in which anisotropic ion flow produces an asymmetric ion atmosphere around the polyelectrolyte, resulting in an orienting torque. From the limiting dichroism at high field, we estimate that the DNA bases are inclined at an angle of 73 degrees or less relative to the helix axis, in good agreement with the revised model of B-form DNA suggested by Levitt, in which the base pairs have a propeller-like twist. Our results establish transient electric dichroism measurements as a technique well suited for study of alterations in the length and base pair inclination of rod-like DNA molecules.
TL;DR: In this paper, the authors analyzed the response of the ionosphere to a suddenly impressed electric field, which is generated by large scale dynamic processes in the magnetosphere such as a sudden compression by an interplanetary shock wave or a change of the magnetospheric convection.
Abstract: SEVERAL kinds of geomagnetic variations are observed simultaneously at high latitudes and in the equatorial region. These are substorms or DP-1 variations, Spq or DP-2 variations, some kinds of pulsations, and the DS-part of SSC and SI. Araki1 analysed the relationship of the preliminary reverse impulse of SC* occurring in the high-latitude and the equatorial regions and found that their occurrence in both regions is well correlated, almost simultaneous, and that the waveforms are very similar. From the characteristics of these geomagnetic variations, it seems that a horizontal electric field impressed in the polar ionosphere from the magnetosphere greatly contributes to the equatorial part of these geomagnetic variations. This electric field is generated by large scale dynamic processes in the magnetosphere such as a sudden compression by an interplanetary shock wave or a change of the magnetospheric convection, and its direction will be approximately east–west (dawn–dusk)2. To clarify the mechanism of the instantaneous horizontal transmission of the polar electric field, we have analysed the response of the ionosphere to a suddenly impressed electric field.
Patent•
26 May 1978TL;DR: In this paper, the use of a light valve for spherical dipolar particle construction is described, and the method of manufacturing the spherical Dipolar Particle Particle (SPP) construction is discussed.
Abstract: A light valve is formed of a plurality of spherical dipolar particles suspended in a matrix material. Each spherical dipolar particle has a unified body formed in three discrete symmetrical sections. A central section is configured to permit light transmission when in a first orientation with respect to a path of light travel, and generally not permit light transmission when in a second, transverse orientation with respect to the path of light travel. A pair of intermediate sections bound the central section and are formed of a transparent material having an electrical permittivity that varies through a range of values as a function of the frequency of an applied electric field. A pair of outer sections bounds the intermediate sections and are formed of a material having a relatively stable electrical permittivity within the range of values of the intermediate sections. An applied electric field at one frequency extreme will cause the spherical dipolar particle to align in the first orientation to permit light transmission, and an applied electric field in the other frequency extreme will cause the particle to anti-align in the second, transverse orientation to shutter or reflect light. The matrix material is preferably formed of a plasticized elastomer that has a plurality of expanded cavities, with each cavity containing an outer lubricating layer to allow free rotational motion of a dipolar particle in the cavity. The use of a light valve of the present invention and method of manufacturing the spherical dipolar particle construction are also disclosed.
TL;DR: The mobility of thermal electrons in xenon varies with the density n : μαnx as discussed by the authors, and is characterized by simple scattering by a polarization field at high gas densities, where the positive value of x is due to the formation of a conduction band and the negative value to scattering by the repulsive cores of the closely spaced atoms.
Abstract: The mobility μ of electrons in xenon varies with the density n : μαnx. For thermal electrons in the gas, x=−1.0 when n<4×1020 molecule/cm3, independent of temperature. This corresponds to pressures ≲20 atm at 300 K and is characteristic of simple scattering by a polarization field. At higher gas densities x becomes more negative, then passes through a minimum, and μ has a positive temperature coefficient at constant n. At these densities thermal electrons form quasilocalized states in, or suffer enhanced scattering by, microscopic regions of relatively high density. The localization effect maximizes in the critical fluid, at n=5×1021 molecule/cm3 and T=290 K, and appears to be negligible again at n?6.8×1021. In the liquid phase x?+9 up to n=1.2×1022 molecule/cm3, then changes to x?−8 at higher densities. The positive value of x is due to the formation of a conduction band, and the negative value to scattering by the repulsive cores of the closely spaced atoms. In the gas and the low density liquid (n<1.2×...
TL;DR: In this article, the orientation of molecular dipoles in polyvinylidene fluoride (PVF2) films under electric field has been measured by ir spectroscopy using ir transparent indium-tinoxide electrodes.
Abstract: Orientation of molecular dipoles in poly(vinylidene fluoride) (PVF2) films under electric field has been measured by ir spectroscopy using ir transparent indium‐tin‐oxide electrodes. Significant changes in ir transmission with electric field have been observed at 512 and 446 cm−1, which demonstrate that crystalline dipoles in β‐phase PVF2 orient along the electric field. As the field is cycled between positive and negative values, the dipole orientation exhibits a hysteresislike behavior, demonstrating that the polarization of β‐phase PVF2 and its switching result directly from the orientation of crystalline dipoles. Time response of dipole orientation shows that the total orientation consists of an instantaneous part and a slowly developing part. Only the latter seems to contribute to the remnant polarization and its switching.
TL;DR: In this paper, the authors show that magnetic field-aligned electric fields in collisionless plasma can be explained by anomalous resistivity or thermoelectric effects based on wave-particle interaction.
Abstract: Mechanisms that may support magnetic-field-aligned electric fields in collisionless plasma are discussed in the light of recent magnetospheric observations, which for the first time allow a quantitative test of the theoretical models Data from barium ion releases which indicate large field-aligned potential drops and direct electric field probe measurements at high altitude which reveal electric fields of several hundred millivolts per meter are discussed It is concluded that the large field strengths observed (1) cannot be explained by anomalous resistivity or thermoelectric effects based on wave-particle interaction, (2) are much larger than required merely to balance the local mirror forces, and (3) are compatible with electric double layers of the same nature as those observed in the laboratory
01 Oct 1978
TL;DR: In this paper, the Imp 6 and Hawkeye satellites were used in a study of very intense electrostatic waves near the upper hybrid resonance frequency in the region just outside the plasmapause, where the polarization of these waves is such that the wave electric field vector is oriented perpendicular to the geomagnetic field.
Abstract: Plasma wave measurements using instruments on the Imp 6 and Hawkeye satellites are utilized in a study of very intense electrostatic waves near the upper hybrid resonance frequency in the region just outside the plasmapause. Studies of these electrostatic disturbances show that the events occur at local times and at magnetic latitudes varying from the equator to 50 deg, and the polarization of these waves is such that the wave electric field vector is oriented perpendicular to the geomagnetic field. In most cases the center frequency of the intense waves corresponds to an (n + 1/2) fg(-) harmonic near the upper hybrid resonance frequency. The hot distribution on function is described for a few events showing temperature anisotropy and a loss cone distribution. A possible mechanism for producing intense waves near the upper hybrid resonance frequency is suggested, and evidence which indicates that the intense electrostatic waves may be a source of nonthermal continuum radiation is given.
TL;DR: In this paper, the authors presented seven arguments in support of the view that discrete auroral arcs are produced by electron acceleration inside electrostatic shocks, as determined from 207 observations on high latitude magnetic field lines.
Abstract: Properties of typical electrostatic shocks, as determined from 207 observations on high latitude magnetic field lines, are summarized. Seven arguments are presented in support of the view that discrete auroral arcs are produced by electron acceleration inside electrostatic shocks.
TL;DR: In this paper, electric field ionization of a molten metal film on a wetted needle is used to generate a liquid cusp at the needle apex, which is then used to produce atomic-ion emission by field ionisation.
TL;DR: In this paper, a theoretical model was developed to classify electrostatic emissions, which appeared to be generated by an unstable electron plasma distribution consisting of cold electrons (less than 100 eV) and hot loss cone electrons (about 1 keV).
Abstract: A scheme was constructed and a theoretical model was developed to classify electrostatic emissions. All of the emissions appear to be generated by the same basic mechanism: an unstable electron plasma distribution consisting of cold electrons (less than 100 eV) and hot loss cone electrons (about 1 keV). Each emission class is associated with a particular range of model parameters; the wide band electric field data can thus be used to infer the density and temperature of the cold plasma component. The model predicts that gyroharmonic emissions near the plasma frequency require large cold plasma densities.
TL;DR: In this paper, the acceleration of a nonneutral stream of charged particles from the surface of an isolated rotating magnetized neutron star in the case where the particle stream flows along the open field lines of a curved poloidal magnetic field was calculated.
Abstract: The paper calculates the acceleration of a nonneutral stream of charged particles from the surface of an isolated rotating magnetized neutron star in the case where the particle stream flows along the open field lines of a curved poloidal magnetic field. It is shown that very large electrostatic potential drops can occur in steady unidirectional space-charge-limited flow along the curved open field lines. The explicit incorporation of magnetic field line curvature is the essential element leading to this new result, assuming that all the charges are supplied by emission from the surface. It is emphasized that the current flow and charge density are unique if all of the assumptions are met, with the result that the accelerating electric field near the stellar surface is quite small compared to the vacuum field.
TL;DR: In this paper, the authors provided a rigorous solution to the problem of combined field and diffusion charging of aerosol particles in the continuum regime, and showed that there is good agreement between the theoretical and experimental results.
TL;DR: In this paper, the authors identify two different processes by which free atoms are ionized in a static electric field, one by tunneling and the other by auto-ionization.
Abstract: We identify two different processes by which free atoms are ionized in a static electric field. The first process is by tunneling and is described accurately by theory developed for hydrogen. The second process, important for all atoms except hydrogen, is similar to autoionization and arises from the effect of level mixing. Data are presented on field ionization in lithium which display behavior due to each of these ionization mechanisms.
TL;DR: In this paper, a new feature of electric field frequency-time spectrograms observed on the S3-3 satellite was used to determine the polarization, frequency, and wavelengths of high-latitude turbulence.
Abstract: A new feature of electric field frequency-time spectrograms observed on the S3-3 satellite, the resonance fingerprint, is used to determine the polarization, frequency, and wavelengths of high-latitude turbulence. It is found that in the rest frame of the plasma the frequency is approximately zero, the wavelength may be as small as 5 m, and the electric field is polarized in the plane normal to the magnetic field. Consequently, the power spectrum below a few hundred hertz as measured by a satellite is dominated by the Doppler shift of zero frequency turbulence. The resonance fingerprint is a characteristic pattern of bite-outs in the electric field power spectrum which repeats at twice the spin frequency of the satellite. The bite-out, an interference effect, is a consequence of the fact that a double probe is insensitive to wavelengths such that the double-probe separation is an integral multiple of wavelength.
TL;DR: In this article, the Green's function solution of the Smoluchowski equation with a Coulomb potential and an electric field was obtained, corresponding to a general boundary condition at the origin, and expressions for the time evolution of quantities such as the rate of geminate recombination and the survival probability were derived.
Abstract: We obtain the Green’s function solution of the Smoluchowski equation with a Coulomb potential and an electric field, corresponding to a general boundary condition at the origin. In the low‐field limit the solution exhibits diffusive behavior for long times, but above a critical field the long‐time decay becomes purely exponential. We derive expressions for the time evolution of quantities such as the rate of geminate recombination and the survival probability, and for t→∞, a→0 (where a is the radius of a perfectly absorbing sphere at the origin) we recover Onsager’s results. We consider a variety of initial conditions, such as a δ function, isotropic and constant distributions, as well as a more complicated distribution applicable to fluorescence quenching in the presence of an electric field. For small values of the electric field and the Laplace transform variable we obtain an expression for the probability of a scavenging reaction taking place in competition with geminate recombination. Using the presc...