Showing papers on "Electric field published in 1976"
TL;DR: In this article, the authors proposed an electro-mechanical model to explain the mechanism of dielectric breakdown and the non-linear I vs. U characteristics of the membrane.
243 citations
TL;DR: In this paper, the dynamo theory of Sq variations is reexamined to see if it can be reconciled with recent observations of ionospheric winds and electric fields.
Abstract: The dynamo theory of Sq variations is reexamined to see if it can be reconciled with recent observations of ionospheric winds and electric fields. Dynamo simulations are performed by using steady winds and both diurnal and semidiurnal tidal winds, observational and theoretical evidence being used to specify the amplitude and phase variations of the winds with altitude. We find that the first negative diurnal tidal mode, present in the upper E and lower F regions of the ionosphere, is capable of accounting for most of the Sq currents. The structure of this tide, which we call the (1, −2)* mode, is significantly influenced by the ion drag force. Lower E region winds, most notably the semidiurnal (2, 4) tidal mode, also contribute somewhat to the Sq currents. Our simulated electric fields using the combined (1, −2)* and (2, 4) modes are in fair agreement with observations; uncertainties in the ionospheric winds as well as errors in obtaining quiet day mean electric fields from the observations can easily account for the remaining discrepancies. Day-to-day variations in the daytime electric fields are probably related to variability of the E region winds. A simulation of electric currents and fields caused by hypothesized magnetospheric sources at quiet times shows that such sources alone cannot account for most of the observed middle- and low-latitude currents and fields, at least during daytime. Clarification of remaining problems requires further observational and theoretical work.
216 citations
TL;DR: In this article, a warm two-fluid theory of soliton formation near the upper-hybrid frequency is developed, and several forms of the nonlinear Schrodinger equation are obtained, depending on whether the electric field is completely perpendicular to the dc magnetic field or whether it has an additional small component parallel to the magnetic field.
Abstract: A warm two‐fluid theory of soliton formation near the upper‐hybrid frequency is developed. Several forms of the nonlinear Schrodinger equation are obtained, depending on whether the electric field is completely perpendicular to the dc magnetic field or whether it has an additional small component parallel to the magnetic field. For the perpendicular case, the character of the soliton depends on its scale length, L, and on β. For low β, when L
209 citations
TL;DR: In this article, the cutoff-frequency/gate-length curves are calculated for uniform and non-uniform channel field distribution in GaAs fets using the fit to the equilibrium Monte Carlo data.
Abstract: A simple model which describes well the nonequilibrium electron transport in GaAs using the fit to the equilibrium Monte Carlo data is suggested In the frame of this model, the cutoff-frequency/gate-length curves are calculated for uniform and nonuniform channel field distribution in GaAs fets The results show that the nonhomogeneity of the electric field in the channel can considerably decrease (by 30%) the maximal frequency of GaAs fets
185 citations
TL;DR: In this paper, the Fokker-Planck equation for an energetic ion beam injected into a magnetized plasma consisting of Maxwellian ions and electrons with υthi ≪υb≪ υthe was studied.
Abstract: The Fokker-Planck equation is studied for an energetic ion beam injected into a magnetized plasma consisting of Maxwellian ions and electrons with υthi ≪υb≪ υthe. The time evolution of the fast ion distribution is given in terms of an infinite sum of Legendre polynomials for distributions that are axisymmetric about the magnetic field. The effect of charge exchange is included. The resulting ion distribution is somewhat isotropic for velocities much less than the injection velocity, however, the distribution is sharply peaked in both energy and pitch angle for velocities near the injection velocity. Approximate asymptotic expressions are given for the distribution in the vicinity of the injected beam and for velocities greater than the injection velocity. The effect of a weak parallel electric field is also given.
171 citations
Patent•
12 Oct 1976
TL;DR: An optical notch filter has a suspension of small absorbing particles which blocks a narrow band of frequencies as discussed by the authors, which can be either a solid matrix as a transmission filter or used on the surface of a mirror as a reflection filter.
Abstract: An optical notch filter having a suspension of small absorbing particles which blocks a narrow band of frequencies. The small absorbent particles are suspended as a colloidal system which can have either a solid, liquid or gas as host material. The absorbing particles can be incorporated in a solid matrix as a transmission filter or used on the surface of a mirror as a reflection filter. The filter can be tuned by an externally applied electric field or by applying hydrostatic pressure.
165 citations
TL;DR: In this article, the dielectric constants of GaAs, CdTe, and ZnSe and their temperature dependences were found from low-frequency capacitance measurements.
Abstract: The dielectric constants of GaAs, CdTe, and ZnSe and their temperature dependences were found from low‐frequency capacitance measurements. From 100 to 300 °K the dielectric constants vary linearly with temperature. No electric field dependence was found up to 104 V/cm, nor frequency dependence between 20 Hz and 1 MHz. The dielectric constants extrapolated linearly to 0 °K are 12.35±0.09, 10.31±0.08, and 8.80±0.07 for GaAs, CdTe, and ZnSe, respectively. The temperature coefficients λ (≡e (0)−1 de/dt) are 2.01×10−4/°K, 2.27×10−4/°K, and 1.71×10−4/°K, respectively, with an accuracy of ±0.02×10−4/°K.
154 citations
TL;DR: In this paper, the nonlinear high-frequency conductance of superlattices due to the nonparabolicity of minizones has been investigated and exact expressions for the current excited with a harmonic electric field are obtained.
Abstract: The nonlinear high-frequency conductance of superlattices due to the nonparabolicity of minizones has been investigated. Exact expressions for the current excited with a harmonic electric field are obtained. A selftransparence effect is predicted. It is shown that in the presence of a strong high-frequency field the increase of the low-frequency oscillations is possible. The frequency doubling and the high-frequency signal detection in the presence of a strong constant electric field is also investigated.
[Russian Text Ignored].
131 citations
TL;DR: In this article, the authors measured the properties of holes trapped in an SiO2 layer by application of a large electric field and found that the maximum number of trapped holes was 4×1012 cm−2 and the centroid of their distribution was 130 A from the Si interface.
Abstract: We have measured the properties of holes trapped in an SiO2 layer by application of a large electric field. The high field (1.4×107 V/cm) was obtained by applying a negative corona charge to the outer SiO2 surface of a Si‐SiO2 structure. The maximum number of trapped holes was 4×1012 cm−2 and the centroid of their distribution was 130 A from the Si interface. All holes were trapped within 320 A of the Si interface. Photodischarge experiments show the level of the trapped holes to be at least 4–5 eV above the valence band edge. We were unable to trap holes in the SiO2 by internal photoemission of holes from the Si. A consistent picture is developed with results that are comparable to those found for trapping holes by irradiation of the SiO2 by a vacuum ultraviolet source.
121 citations
TL;DR: In this paper, the ambient electric field required for sustained positive corona streamer propagation is determined as a function of dry air pressure and water vapor partial pressure, and it is shown that the critical field is inversely proportional to the length of the trail that is effectively conducting and is dependent on the lifetime of low-energy electrons against attachment.
Abstract: Experiments are described in which the ambient electric field required for sustained positive corona streamer propagation is determined as a function of dry air pressure and water vapor partial pressure. This critical field varies approximately as the 1.5 power of the dry air pressure and shows a strong linear dependence on the water vapor partial pressure. These results differ substantially from what would be expected on the basis of Paschen’s Law, but are consistent with a propagation mechanism in which the ionizing streamer tip and a portion of the plasma trail left behind it are treated as an electrically isolated propagating conductor. Energy budget arguments indicate that the critical field is inversely proportional to the length of the trail that is effectively conducting and is dependent, therefore, on the lifetime of low‐energy electrons against attachment.
113 citations
TL;DR: In this article, the motion of charged particles is examined in the case of a homogeneous magnetic field B together with an orthogonal electric field E, which has a gradient ▽E parallel to B. If B 2 q 2 m 2 − q▽E m > 0, the particles drift at right angles to E and B with a modified gyrofrequency and produce a current in that direction.
TL;DR: In this article, the authors modeled the interface between two miscible fluids which have identical mechanical properties but disparate electrical conductivities and are stressed by an equilibrium tangential electric field, and derived over-stable (propagating) modes in terms of the complex growth rate and fastest growing wavenumber.
Abstract: The interface between two miscible fluids which have identical mechanical properties but disparate electrical conductivities and are stressed by an equilibrium tangential electric field is studied experimentally and theoretically. A bulk-coupled electrohydrodynamic instability associated with the diffusive distribution of fluid conductivity at the interface is experimentally observed.The configuration is modelled using a layer of exponentially varying conductivity spliced on each surface to a constant-conductivity fluid half-space. Over-stable (propagating) modes are discovered and characterized in terms of the complex growth rate and fastest growing wavenumber, with the conductivity ratio and an inertia-viscosity time-constant ratio as parameters. In the low inertia limit, growth rates are governed by the electric-viscous time τ = η/eE2. Instability is found also with the layer of varying conductivity bounded by rigid equipotential walls. A physical mechanism leading to theoretically determined fluid streamlines in the form of propagating cells is described.At relatively high electric fields, large-scale mixing of the fluid components is observed. Photocell measurements of distributions of average fluid properties demonstrate evolution in time on a scale determined by τ.
TL;DR: In this article, a numerical technique is used to calculate electric fields and currents between 0- and 150-km altitude produced by large-scale horizontal electric fields known to exist in the polar cap and auroral ionosphere.
Abstract: The main purpose of this paper is to draw attention to the important but long neglected problem of electrical coupling between the ionosphere and the lower atmosphere. A numerical technique is used to calculate electric fields and currents between 0- and 150-km altitude produced by large-scale horizontal electric fields known to exist in the polar cap and auroral ionosphere. A two-dimensional model assuming a flat earth and a vertical geomagnetic field is used. The results show that horizontal electric fields in the ionosphere map down to ∼ 10 km with little attenuation, in agreement with previous authors' results. In addition, these horizontal ionospheric electric fields should cause significant modulations of vertical electric fields down to the earth's surface. The effects of conductivity irregularities in the ionosphere, stratosphere, and troposphere are also examined. Localized conductivity enhancements associated with aurora are expected to produce a horizontal electric field of up to a few millivolts per meter at ∼30-km altitude in the absence of any horizontal field in the ionosphere. These conductivity enhancements have less than a 1% effect on the vertical electric field on the ground. The effects of stratospheric and tropospheric irregularities are negligible at large heights but become important below ∼20 km. Their magnitude depends on how the ratio between the local resistivity and the height-integrated columnar resistance is altered.
TL;DR: In this article, the authors used the retarding potential analyzer on the AE-C satellite to determine the shape of the ion velocity distribution in the velocity plane perpendicular to the magnetic field direction.
Abstract: The action of strong dc electric fields at high latitudes combined with a predominance of ion-neutral collisions has for some time been expected to create appreciable departures of the ion velocity distribution from the equilibrium Maxwellian configuration. We present new evidence gathered with the retarding potential analyzer on the AE-C satellite that shows that the ion velocity distribution departs significantly from the Maxwellian shape at ion temperatures greater than 1500degreeK. From the analysis of more than 50 volt-ampere characteristics we have determined the shape of the ion velocity distribution in the velocity plane perpendicular to the magnetic field direction. Theoretical analysis shows that the use of a relaxation model for the description of ion-neutral collisions gives velocity distributions for both O/sup +/ and molecular ions that are qualitatively correct. However, the departures from the Maxwellian configuration are always exaggerated by the theory. An immediate consequence is that the threshold for the onset of the Ott and Farley microinstability caused by the double-hump character of the velocity distribution must be increased to at least 80 mV/m. Finally, if the ion temperature exceeds 2000degreeK, we find that the interpretation of the retarding potential analyzer data can be seriously affected by the usemore » of the normally assumed Maxwellian ion velocity distribution in the data inversion process. For very strong electric fields, ion temperatures can be underestimated by more than 2000degreeK, and composition ratios can be affected by more than a factor of 2. Other ground-based or in situ measurements should be similarly affected. (AIP)« less
TL;DR: In this article, it was shown that the electronic contribution to the field gradient is largely responsible for the observed temperature dependence of non-cubic metals, i.e., the T √ 3 √ 2 −1 2 −2 −1 −1, and that the conclusions are general and apply to all non cubic metal types.
Abstract: Temperature dependence of the nuclear quadrupole frequency, ${\ensuremath{
u}}_{Q}$, of noncubic metals has been studied theoretically. It is shown that the electronic contribution to the field gradient is largely responsible for the observed ${T}^{\frac{3}{2}}$ behavior. The conclusions are general and apply to all noncubic metals.
Patent•
20 Jul 1976
TL;DR: In this paper, an electric field is generated across two electrodes or one electrode and ground, and is passed through both the tumor and the surrounding tissue, and the polarity of the electric fields is varied at radio frequency.
Abstract: Apparatus is described for heating tissue and which is particularly useful for treating tumors in humans and animals. An electric field is produced across two electrodes or one electrode and ground, and is passed through both the tumor and the surrounding tissue. The polarity of the electric field is varied at radio frequency. The power of the electric field is efficiently coupled into the tissue being heated. Direct current inverse feedback circuitry enables close control of tissue temperatures.
TL;DR: In this paper, the Stark energies for different states of a hydrogen atom in a uniform electric field calculated by the Rayleigh-Schrodinger perturbation theory and diagonal Pade approximants are compared with the results of exact numerical calculations.
Abstract: For pt.III see ibid., vol.12, p.2637 (1979). Stark energies for different states of a hydrogen atom in a uniform electric field calculated by the Rayleigh-Schrodinger perturbation theory and diagonal Pade approximants are compared with the results of exact numerical calculations. Certain general conclusions are formulated.
TL;DR: In this paper, the authors used the slow time dependences of the high-frequency small-signal capacitance and the current of a space charge region which is depleted of carriers.
Abstract: Charges trapped at imperfection centers can be detected by observing the slow time dependences of the high-frequency small-signal capacitance and the current of a space charge region which is depleted of carriers. Detection of as low as 1010 to 1011 trapped electron charges per cm3 in a volume of 10−3 cm × 10−3 cm2, or 105 to 10 electron charges, can be achieved. This technique has been used to study the temperature, electric field and photon energy dependences of the thermal, optical and Auger-impact emission and capture rates of electrons and holes at impurity and defect centers in depleted bulk and surface space charge regions in semiconductors, as well as the generation, annealing and diffusion kinetics of these centers. It has also been used to monitor the silicon integrated circuit fabrication processes. The principle of this technique is described and experimental examples are given to illustrate the applications of the technique.
TL;DR: In this paper, the breakdown voltage of abrupt cylindrical and spherical junctions has been obtained, using suitable approximations for the electric field in the depletion layer, using a single curve for each situation.
Abstract: Analytical solutions for the breakdown voltage of abrupt cylindrical and spherical junctions have been obtained, using suitable approximations for the electric field in the depletion layer. These solutions are shown to be within ±1% of exact computer solutions for doping densities of less thant 10 16 cm −1 . By normalization to the parallel plane case, these solutions have been presented in a form which allows the computation of the breakdown voltage of both cylindrical and spherical junctions using a single curve for each situation.
TL;DR: In this article, the energy level spacings for electrons and holes in surface-charge layers on Si(100) are determined from a measurement of direct optical absorption of far-infrared laser radiation guided along the surface.
Abstract: The energy-level spacings for electrons and holes in surface-charge layers on Si(100) are determined from a measurement of direct optical absorption of far-infrared laser radiation guided along the surface. At photon energies in the range 5.64-15.81 meV, the separation of the electric subbands is measured as a function of the surface-charge density ${N}_{s}$. For a comparison of the experimental results with theory we have characterized our metal-oxide-semiconductor system with the help of capacitance versus voltage measurements. At fixed values of ${N}_{s}$, we have examined the subband energies as a function of a substrate bias electric field. In the course of this work the influence of visible radiation on the resonance in surface-charge layers has been noted.
TL;DR: In this paper, a numerical model is used to calculate the electric field enhancement in a thundercloud due to the propagation of a growing system of positive corona streamers, such as might be initiated by a hydrometeor.
Abstract: A numerical model is used to calculate the electric field enhancement in a thundercloud due to the propagation of a growing system of positive corona streamers, such as might be initiated by a hydrometeor. These streamers intensify if the ambient electric field E exceeds a critical value E0, which is experimentally determined. The positive charge carried in the head of the system increases in magnitude, and the negative charge is deposited in the trail, and thus an electric dipole that tends to enhance the original field is created. The growth is calculated by solving an energy balance equation for the system, including the potential energy of the dipole, the losses due to ionization and excitation, and the production of new streamer tips. Several systems may propagate sequentially, each one passing into the debris of its predecessors and growing more vigorously as a result. For representative values of E and E0 at 6.5-km altitude it is shown that a series of three to seven such systems can give rise to local enhancement of the ambient electric field up to 15×105 V/m over a distance of a few meters, which is sufficient to insure dielectric breakdown and possibly launch the stepped leader.
TL;DR: The results indicate that peak power absorption densities as high as 5.63 W/kg can be produced in man exposed to 10 mW/cm2 31 MHz radiation fields and show that the absorption decreases as the square of the frequency as predicted by theory for frequencies below 31 MHz.
Abstract: When the body of man, small compared to a wavelength, is exposed to high frequency (HF) electromagnetic (EM) fields, the absorbed power density patterns and total absorbed power may be approximated by the simple superposition of the internal electric fields obtained from the quasistatic coupling characteristics of the electric and magnetic field components determined independently. These characteristics were obtained for full scale man by thermographic studies of power absorption in scale models of man exposed to fields at frequencies scaled up inversely proportional to the model size. A VHF resonant cavity was used to provide the necessary field strengths for producing measurable power absorption patterns under simulated HF exposure conditions. The results indicate that peak power absorption densities as high as 5.63 W/kg can be produced in man exposed to 10 mW/cm 2 31 MHz radiation fields. The results show that the absorption decreases as the square of the frequency as predicted by theory for frequencies below 31 MHz.
TL;DR: In this paper, a lightning discharge is modeled as an impulse current from cloud to ground which instantaneously removes a quantity of charge from a charge center originally screened by a neutralizing space charge.
Abstract: A lightning discharge is modeled as an impulse current from cloud to ground which instantaneously removes a quantity of charge from a charge center originally screened by a neutralizing space charge. The resulting time-dependent electric and magnetic fields at the ground and in the upper ionosphere are examined for a time interval that is long in comparison to the duration of a typical discharge but short in comparison to the relaxation time of the screening space charge. The calculations are carried out for a nominal nighttime ionosphere with an assumed exponential conductivity profile and with anisotropy taken into account. First, analytic approximations are obtained for the various ULF transfer functions of the medium throughout the entire altitude range between the ground and the upper ionosphere. The transfer functions are then used to obtain analytic expressions for the ULF component of the time-dependent fields produced by the assumed source. At the ground the fields result from electric relaxation of the ionosphere and persist for times of a few seconds. The decay time of the electric field at the ground decreases with increasing distance from the source. The time dependence of the fields can be explained on the basis of a simple variable capacitor model of the medium. In the upper ionosphere there is an outgoing hydromagnetic pulse which arises from a resonant excitation of the ionosphere by the low-frequency components of the discharge itself. The duration of the pulse seems too short to excite geomagnetic pulsations in the magnetosphere.
TL;DR: In this paper, the aerodynamic interaction between electrically charged cloud drops in the presence of vertical external electric fields was numerically investigated for 800 mb and +10°C.
Abstract: The aerodynamic interaction between electrically charged cloud drops in the presence of vertical external electric fields was numerically investigated for 800 mb and +10°C. The collector drops had radii between 11.4 and 74.3 µm while the collected drops had radii between 1 and 66 µm. The external electric fields considered ranged between 0 and 3429 V cm−1 (=3.429×105V m−1 and the electric charge on the cloud drops ranged between 0 and 1.1×10−4 (=3.7×10−14 C). The results demonstrate that the presence of electric charges and fields of magnitudes observed during thunderstorm and pre-thunderstorm conditions drastically enhance the collision efficiency of cloud drops. The enhancement was found to he most pronounced for the smallest collector drops studied.
TL;DR: In this paper, a new mechanism of superconductivity based upon the pairing of the spatially separated electrons and holes due to their Coulomb attraction is presented, and the possible experiments are discussed.
TL;DR: In this article, an impact ionization model was proposed to predict negative-resistance type of SiO2 dielectric instability, where electrons are injected from the cathode, the electron distribution is heated, hot electrons ionize the lattice, and the residual positive charge distorts the electric field and further increases impact ionisation.
Abstract: Dielectric instability and breakdown in SiO2 have been well characterized by many experimental techniques, including measurements of thickness dependence, contact barrier dependence, and time dependence of breakdown as well as a determination of radiation sensitivity and prebreakdown charge buildup within the insulator. All of the various types of data can be explained consistently by an impact ionization model, which predicts a negative‐resistance type of instability; electrons are injected from the cathode, the electron distribution is heated, hot electrons ionize the lattice, and the residual positive charge distorts the electric field and further increases impact ionization. The model is sensitive to two key parameters, the ionization bandgap Ei, and the electron–phonon scattering length λ.
TL;DR: In this article, a nonlinear relationship between the mean free path length for absorption and the applied electric field indicates the existence of hot electrons in liquid argon, and the recombination effect in the ionization column produced by α-particles is enhanced by oxygen and nitrogen impurities.
TL;DR: In this article, a model of the electrostatic field above an auroral arc is proposed in which the magnetic field lines are not all equipotentials and use is made of recent theoretical work on oblique current-driven electrostatic shocks to demonstrate the plausibility of nonequipotential field lines.
Abstract: Shaped charge barium release data and high-speed auroral image data show the likely existence of anomalously large (about 1 V/m referred to the 100-km level) electric fields at distances the order of one earth radius above the earth. A model of the electrostatic field above an auroral arc is proposed in which the magnetic field lines are not all equipotentials. Use is made of recent theoretical work on oblique current-driven electrostatic shocks to demonstrate the plausibility of nonequipotential field lines. The model is addressed to the structure of inverted-V electron spectra, current continuity between magnetosphere and ionosphere, and the results of recent shaped charge barium experiments. The model is used to identify specific gaps in our understanding of auroral phenomena.
TL;DR: In this article, the characteristics of pairs of oppositely directed spikes in ionospheric convection velocities (or shear flow reversals), as first described by Gurnett, have been conducted by using data from Atmosphere Explorer C.
Abstract: A study of the characteristics of pairs of oppositely directed spikes in ionospheric convection velocities (or shear flow reversals), as first described by Gurnett, has been conducted by using data from Atmosphere Explorer C. These phenomena tend to occur near the large-scale reversal from sunward to antisunward convection on the nightside of the earth. Generally, the spikelike shear flow reversals involve electric field components along the spacecraft orbit that are directed toward the region between them, in which inverted V type electron precipitation is observed. This relationship between the electron precipitation and the electric field spikes is consistent with an upward-flowing field-aligned current that is fed by Pedersen currents from the adjacent regions of strong convection. In one case a divergent equivalent electric field structure was observed, that is, with the spikelike electric fields pointing away from the region in between, which in this case exhibited a sharp electron flux dropout. This opposite configuration may be an example of counterparts to inverted V structures existing in regions of downward-flowing field-aligned currents.