Showing papers on "Electric field published in 1971"
TL;DR: In this article, the E-layer conductivity may be too small to close this circuit, so that polarization fields build up in the F-layer, causing the plasma to drift with the wind.
427 citations
TL;DR: In this article, a theory, valid for both steady and alternating fields, was developed which predicts the conditions leading to oblate and prolate spheroids, and which reduces to Taylor's equations for conducting dielectrics in steady fields and to the equations for perfect dielectric in alternating fields.
Abstract: In 60 Hz electric fields, liquid drops suspended in a second immiscible liquid deformed into prolate spheroids oriented in the direction of the field in 22 drop/medium combinations studied experimentally. In steady fields, oblate or prolate spheroids were formed depending upon the dielectric constants and resistivities of the drop and medium. In systems yielding oblate spheroids, a critical frequency existed at which the drop remained spherical at all field strengths. Electrohydrodynamic streaming near the surface of the drop occurred as predicted by Taylor. A theory, valid for both steady and alternating fields, was developed which predicts the conditions leading to oblate and prolate spheroids and which reduces to Taylor's equations for conducting dielectrics in steady fields and to the equations for perfect dielectrics in steady and alternating fields. The theory explains the general types of deformation and electrohydrodynamic flow which were observed and predicts several interesting new modes of behaviour. In most cases the measured deformations were greater than calculated from the theory; various explanations for this discrepancy are advanced, but no definite conclusions are reached. At high field strengths the drops burst in two basically different ways which we have designated as electric and electrohydrodynamic burst, the first caused by electric stresses alone and the second by a combination of electric and hydrodynamic stresses.
336 citations
TL;DR: In this article, the adiabatic theory for charged particles moving in a region where the main component of the magnetic field reverses its direction is presented for charge-reconnection geometry.
Abstract: The adiabatic theory is presented for charged particles moving in a region where the main component of the magnetic field reverses its direction. The unperturbed field configuration is one-dimensional and involves two regions of uniform and opposite magnetic fields separated by a reversal region of small but finite extent. The adiabatic theory is capable of describing particle orbits when gradual spatial and/or temporal field variations are added to this configuration. Several applications are given. These include orbits during a null-sheet compression, orbits in the sheets studied by Alfven and Speiser, and orbits in the vicinity of the magnetic null line of the so-called field-reconnection geometry.
302 citations
TL;DR: Several interesting side effect phenomena coincident with nonuniform electric field conditions were observed, including stirring (related to "jet" effects at localized electrode sites), discontinuous repulsions, and cellular rotation which was found to be frequency dependent.
288 citations
TL;DR: In this paper, the field-effect mobility of electrons in inversion layers of Si as functions of the crystalline orientation of the surface and of the azimuthal direction of the current path within the layers is reported.
Abstract: Measurements of the field-effect mobility of electrons in $n$-type inversion layers of Si as functions of the crystalline orientation of the surface and of the azimuthal direction of the current path within the layers are reported. Significant mobility anisotropy observed over a range of strong electric fields perpendicular to the surface at temperatures from 77 to 320 \ifmmode^\circ\else\textdegree\fi{}K contrasts substantially with that in the case of $p$-type inversion layers reported previously. The anisotropy at room temperature can be successfully interpreted in terms of the effective-mass anisotropy calculated on the basis of Stern and Howard's formula for the two-dimensional carriers. For a full understanding of the experimental results, particularly at low temperatures, theoretical investigations including the anisotropy of the relaxation time are required, but have not been explored enough. Extensive data on the dependences of the mobility on the electric field and temperature as well as bulk-acceptor concentration are presented and discussed in the light of existing scattering theories. Some hole-mobility data are included for comparison.
280 citations
TL;DR: In this article, the drift velocity of electrons and holes in high purity silicon has been measured, with the time of flight technique, as a function of electric field (0·1−50 KV/cm) at several temperatures between 77 and 300°K.
248 citations
TL;DR: In this article, an extension of the Helfrich theory of hydrodynamic instabilities to the case of alternating electric fields is presented, where the electrohydrodynamic effects are described by two coupled equations for the charge density (q) and the local curvature of the molecular alignment (ψ).
Abstract: We present an extension of the Helfrich theory of hydrodynamic instabilities to the case of alternating electric fields. The electrohydrodynamic effects are described by two coupled equations for the charge density (q) and the local curvature of the molecular alignment (ψ). The relaxation time for q is the dielectric relaxation time τ (∼ 10-2 s in typical samples). The relaxation time T for ψ is strongly dependent on the field magnitude. Provided that the sample thickness d is above a certain limit dc, the nature of the instability is very different, depending on the ratio of the field frequency ω to a critical frequency ω c. For ω ωc the situation at threshold corresponds to a constant q and an oscillating ψ. These predictions, together with the calculated curves of threshold voltage vs ω and d, are in reasonable agreement with a number of recent experiments.
236 citations
TL;DR: In this article, the role of charge separation due to splashing in thunderstorm electrification and in the build-up of space charges during rainfall is discussed and mechanisms for the formation and breakup of the crown are proposed.
Abstract: The charges separated by splashes on solid and wetted surfaces are shown to be carried on the liquid fragments ejected from the crown. Experimental observations on the nature of these splashes are presented and mechanisms for the formation and break-up of the crown are proposed. The surface on which a splash occurs is generally left with a positive charge, the magnitude of which decreases with increasing concentration of solute in the drop. This is explained by the disruption of the electrical double layer. When drops containing ammonium hydroxide in excess of 2.5 x 10-5 mol 1_1 splash on ice at — 1 °C the ice receives a positive charge. In this case, freezing potentials appear to play a role in the charging. In an applied electric field the charges separated by splashing increase as the field is increased, in agreement with an induction mechanism of charging. Also, in an applied electric field, the charges initially increase as the impact speed is increased but beyond a certain impact speed the charges decrease. This is explained in terms of the relative magnitudes of the time of contact of the ejected liquid fragments with the crown and the relaxation time of charge carriers in the liquid. The role of charge separation due to splashing in thunderstorm electrification and in the build-up of space charges during rainfall is discussed.
215 citations
TL;DR: In this paper, the theory of dissipation of ionospheric electric currents is extended to include viscosity, and conditions for significant heating by field-aligned currents are derived.
198 citations
TL;DR: The voltage dependence of photo-injected currents in SiO2 films for electric fields less than about 106 V/cm exhibits anomalous behavior as discussed by the authors, and the physical mechanism responsible for this behavior is the scattering of photoinjected electrons in the SiO 2 image force potential well between the emitter and the potential maximum.
Abstract: The voltage dependence of photoinjected currents in SiO2 films for electric fields less than about 106 V/cm exhibits anomalous behavior It is shown that the physical mechanism responsible for this behavior is the scattering of photoinjected electrons in the SiO2 image force potential well between the emitter and the potential maximum A previously published model attributing the effect to electron trapping in SiO2 is shown to be inconsistent with the experimental results A theoretical model is presented and the voltage dependence of photocurrents is derived including the effects of scattering and barrier lowering Experimental results from MIS structures using thermally grown SiO2 are found to be in excellent agreement with theoretical predictions when a 34 A mean free path for scattering in SiO2 is used in the model
194 citations
TL;DR: In this article, the electric field and temperature dependence of excitonic electroabsorption for direct-band-gap semiconductors and insulators were investigated. But the authors focused on the single-particle electro absorption theory.
Abstract: The electric field and temperature dependence of excitonic electroabsorption is presented for direct-band-gap semiconductors and insulators. Each excitonic electroabsorption spectrum is characterized in terms of three energy parameters: (i) $R$, the binding energy of the exciton; (ii) $\ensuremath{\Gamma}$, the thermal broadening parameter; and (iii) $\ensuremath{\hbar}\ensuremath{\theta}$, the electro-optical energy. The relative magnitude of these three quantities determines which, if any, of the competing forces dominate. In comparison with the single-particle electroabsorption theory, the excitonic electroabsorption theory gives several new results. The electric field and temperature dependence of ${\ensuremath{\epsilon}}_{2}$, $\ensuremath{\Delta}{\ensuremath{\epsilon}}_{2}$, and $\ensuremath{\Delta}{\ensuremath{\epsilon}}_{1}$ are displayed. Fitting of the excitonic electroabsorption theory to lead iodide data gives the values of 2.58 eV for the direct gap in lead iodide and 0.21 electron masses for the reduced mass of the electron-hole pair associated with the extrema in the valence and conduction bands, as compared with previous values of 2.55 eV and 0.24 electron masses.
01 Jan 1971
TL;DR: In this paper, conduction and absorption-current measurements up to about half the breakdown field have given clear evidence of space charge effects in polythene, and the apparent intrinsic electric strength under various modes of stressing was obtained from measurements of the apparent ‘intrinsic’ electric strength.
Abstract: There has been speculation in the past about the extent to which space charge formed by the flow of prebreakdown current affects the electric strength of polythene In the present work, conduction and absorption-current measurements up to about half the breakdown field have given clear evidence of space-charge effects Further evidence was obtained from measurements of the apparent ‘intrinsic’ electric strength under various modes of stressing It was found that the electric strength of polythene measured with direct voltage below about 30°C exceeded the corresponding value measured with impulse voltages by up to about 25% The impulse electric strength could be increased to equal the direct voltage by prestressing each specimen for 4min with direct voltage of the same polarity as the impulse voltage However, when the impulse was of opposite polarity to the direct prestressing voltage, the electric strength decreased with increase in the prestressing field The effect was dramatic, for the impulse electric strength changed from the normal value of about 6MV cm−1 to less than 2MV cm−1 as the prestressing field was increased to about 75% of the electric stength measured with direct voltage Experiments in which the breakdown impulse was applied some time after removal of the prestressing field showed that the impulse electric strength at 20°C recovered in about 10−2s to the value obtained with impulses without prestressing Thus the prestressing caused no permanent damage The observed effects are attributed to space-charge injection from the electrodes The observations are not consistent with the concept that breakdown occurs when the field at a point within the specimen exceeds a critical value, the intrinsic electric strength of polythene
TL;DR: In this article, the threshold ac electric field required for the excitation of the purely growing "oscillating two-stream" and decay instabilities is found to increase when the density gradient scale length H becomes less than the mean free path.
Abstract: The threshold ac electric field required for the excitation of the purely growing “oscillating two‐stream” and decay instabilities is found to increase when the density‐gradient scale length H becomes less than the mean free path. For a plasma with no magnetic field, the threshold field is given by E2/4πnTe≈2(k‖H)−1, where k‖≲(1/4)D−1 is the wavenumber of the instability in the direction orthogonal to the density gradient. (D is the electron Debye length.) Qualitative arguments suggest that this result should hold in the presence of a magnetic field. Recent experimental measurements of the threshold field agree well with these theoretical calculations. The reason for the threshold field increasing is that, in an inhomogeneous plasma, the unstable region has a finite extent spatially and energy (in the form of electron plasma waves) can propagate out of this region, thus creating an energy loss not found in uniform plasmas.
TL;DR: Low energy particle plasma sheet and convection electric field distributions over auroral zones and polar caps from satellite Injun 5 observation as mentioned in this paper were obtained by using the Injun-5 data set.
Abstract: Low energy particle plasma sheet and convection electric field distributions over auroral zones and polar caps from satellite Injun 5 observation
TL;DR: The extended Poole-Frenkel model as mentioned in this paper includes the variation of the barrier height with electric field in directions both opposite and forward to the electric force on an electron and the equation for the voltage-current characteristics based on this model gives not only the usual Poole Frenkel equation at extremely high electric fields but also Ohm's law at low fields.
Abstract: The extended Poole‐Frenkel model presented here includes the variation of the barrier height with electric field in directions both opposite and forward to the electric force on an electron The equation for the voltage‐current characteristics based on this model gives not only the usual Poole‐Frenkel equation at extremely high electric fields but also Ohm's law at low fields Several published experimental data are in good agreement with this equation
TL;DR: In this paper, the authors developed a theoretical solution for the electromagnetic response of a two-dimensional inhomogeneity in a conductive half-space, in the field of a line source of current.
Abstract: A theoretical solution is developed for the electromagnetic response of a two‐dimensional inhomogeneity in a conductive half‐space, in the field of a line source of current. The solution is in the form of an integral equation, which is reduced to a matrix equation, and solved numerically for the electric field in the body. The electric and magnetic fields at the surface of the half‐space are found by integrating the half‐space Green’s functions over the scattering currents. One advantage of this particular numerical technique is that it is necessary to solve for scattering currents only in the conductor and not throughout the half‐space. The response of a thin, vertical conductor is studied in some detail. Because the only interpretational aids available previously were scale model results for conductors in free space, the results presented here should be useful in interpreting data and in designing new EM systems. As expected, anomalies decay rapidly as depth of burial is increased, due to attenuation in...
TL;DR: In this paper, it was shown that dc, ac, or hf electric field acts across a vertical tube filled with a mixture of natural gas (CH4) or ethylene and air at 1 atm, the speed of flame propagation is shown to rise well above its value in zero field; however, no effect is found in town gas-air mixtures.
TL;DR: In this paper, an analysis of the effects of oxide space charge on the voltage dependence of photo-injected currents is presented, and it is shown that effective charge distributions in SiO2 can provide information about the spatial location of oxide charge.
Abstract: Determination of the nature and distribution of oxide charge in MOS structures is important to an understanding of oxide charging phenomena. In addition to their relevance to device failure mechanisms, it appears that charging phenomena may be used to advantage in memory device applications. The physical mechanism dominating the voltage dependence of photoinjected currents in SiO2 is the scattering of electrons in the region of the oxide between the injecting electrode and the image force potential maximum. Since the spatial position of the potential maximum depends on the electric field resulting from space charge in the oxide as well as the field due to the applied voltage, analysis of the V‐I characteristics of photoinjected currents can provide information about the spatial location of oxide charge. Presented in this paper are the results of an analysis of the effects of oxide space charge on the voltage dependence of photoinjected currents. It is shown that effective charge distributions in SiO2 can ...
TL;DR: Magnetospheric plasma convection electric field double-probe measurement at high latitude by Injun-5 satellite, noting east-west velocity reversals or discontinuities at auroral zone.
Abstract: Magnetospheric plasma convection electric field double-probe measurement at high latitude by Injun-5 satellite, noting east-west velocity reversals or discontinuities at auroral zone
TL;DR: In this article, it is shown that when an arbitrary external field is applied, the constitutive relation P=(e−1)/4 πE between the local polarization and the local macroscopic electric field is valid under some completely acceptable restrictions.
Abstract: A molecular fluid of identical molecules with a rigid dipole moment in an arbitrarily shaped volume is considered. The volume may or may not be embedded in a dielectric continuum. It is shown that when an arbitrary external field is applied, the constitutive relation P=(e−1)/4 πE between the local polarization and the local macroscopic electric field is valid under some completely acceptable restrictions. In the establishment of this relation a crucial role is played by a long‐range part of the two‐particle correlation function, for which an explicit expression is obtained. One term in this long‐range part is explicitly dependent on the shape of the sample volume and on the surroundings. The resulting dielectric constant of the molecular fluid can be formally expressed in only the local interactions of the molecules and is thus independent of the surroundings and the shape of the sample.
TL;DR: In this article, it was shown that propagation in a non-uniform medium increases the nonlinear penetration effect; the maximum non-relativistic plasma frequency which allows transmission of a strong wave is ${{\ensuremath{\omega}}_{p}}^{2} 2}, where p is the electric field in the absence of a plasma.
Abstract: We report two new results concerning the propagation of electromagnetic waves with a strength parameter $\ensuremath{
u}=\frac{\mathrm{eE}}{m\ensuremath{\omega}c}$ sufficiently large ($\ensuremath{
u}\ensuremath{\gg}1$) to cause relativistic electron velocities. The first is an analytic solution of the nonlinear equations for linearly polarized waves in a uniform medium. The second is that propagation in a nonuniform medium increases the nonlinear penetration effect; the maximum nonrelativistic plasma frequency ${\ensuremath{\omega}}_{p}$ which allows transmission of a strong wave is ${{\ensuremath{\omega}}_{p}}^{2}\ensuremath{\approx}{(\frac{\ensuremath{\omega}L}{c})}^{\frac{1}{2}}\frac{e{E}_{i}\ensuremath{\omega}}{\mathrm{mc}}$, where $L$ is the density-gradient scale length and ${E}_{i}$ the electric field in the absence of a plasma.
TL;DR: In this article, the authors extended the theory of optical activity to include the effects of the electric dipole induced by the electric field gradient of the electromagnetic wave as well as that of electric quadrupole induced from the electric fields.
Abstract: The established theory of optical activity relates the activity to the mean electric dipole induced by the time-derivative of the magnetic field of the light wave and to the associated mean magnetic dipole induced by the time-derivative of the electric field. The results is adequate for the interpretation of the average activity in an isotropic medium, but not for components of the activity along different molecular axes. The theory is extended to include the effects of the electric dipole induced by the electric field gradient of the electromagnetic wave as well as that of the electric quadrupole induced by the electric field. The resulting expression for any component of the optical activity is independent of the choice of origin.
TL;DR: In this paper, the drift of charge carriers in thin vitreous films of arsenic triselenide has been examined by a transit time technique, and it was found that the hole mobility was strongly dependent on temperature and applied electric field.
Abstract: The drift of charge carriers in thin vitreous films of arsenic triselenide has been examined by a transit time technique. The specimens used were prepared by cooling from the molten state, rather than by evaporation. Electron mobility measurements were found to be impractical, the mobility being estimated as less than 10−10 m2 v−1 sec−1 at room temperature. The hole mobility was measurable, however, and was found to be strongly dependent on temperature and applied electric field. The hole transit pulses were of a ‘rounded’ form, indicating a spread of carrier transit times. The field dependence was of a form attributable to the Poole–Frenkel effect (field-stimulated emission of carriers from charged trapping centres). After extrapolation of the measurements to zero applied field, the temperature dependence of the mobility indicated an activation energy of about 0·43 ev. These results, and those of a subsidiary examination of the temperature and field dependence of the specimen conductivity, are d...
TL;DR: Polar cap electric field measurements and model for Hall current auroral electrojet continuity and polar cap magnetic disturbances are presented in this article, where the model is extended to include magnetic disturbances.
Abstract: Polar cap electric field measurements, and model for Hall current auroral electrojet continuity and polar cap magnetic disturbances
01 Jun 1971
TL;DR: In this article, a method is described for tracing theoretically the growth in space and time of a rapidly developing gaseous discharge between parallel-plate electrodes where the electric field is distorted by the space charge of the electrons and ions.
Abstract: A method is described for tracing theoretically the growth in space and time of a rapidly developing gaseous discharge between parallel-plate electrodes where the electric field is distorted by the space charge of the electrons and ions. The results obtained for a discharge in nitrogen initiated by a pulse of electrons leaving the cathode have been used to simulate streak photographs of the light output from the discharge. There is excellent agreement between the present results and the experimental streak photographs of Wagner. It is concluded that the occurrence of the anode- and cathode-directed streamers can be satisfactorily explanined in terms of the basic Townsend ionisation processes, provided that space-charge distortion of the field is allowed for correctly.
TL;DR: In this paper, a pump frequency near 3 GHz is used to parametrically amplify the sound wave at one half the pump frequency and this process forms a method of generating sound waves throughout the crystal volume.
Abstract: The parametric interaction between two oppositely traveling sound waves and a nonspatially varying (k = 0) rf electric field in lithium niobate is illustrated in this paper. A pump frequency near 3 GHz is used to parametrically amplify the sound wave at one‐half the pump frequency. In addition with a pump field that is sufficiently strong parametric oscillations occur within the crystal and this process forms a method of generating sound waves throughout the crystal volume. Finally, we have found that this type of parametric mixing of two sound waves can be used to obtain convolution signals in real time by monitoring the electric polarization generated within the crystal at twice the signal frequency.
TL;DR: In this paper, the electric resonance spectrum of PH3 was measured at zero electric field for three rotational states, J=4, 5, and 7 with K=3, and the dipole moment (debye) is 0.57395±0.0003.
Abstract: The electric resonance spectrum of phosphine (PH3) was measured at zero electric field for three rotational states, J=4, 5, and 7 with K=3. In addition, the J=K=2 and J=K=1 spectra were observed at several values for the electric field. The dipole moment (debye) is 0.57395±0.0003. The magnetic hyperfine constants (kilohertz) are cα=−114.90±0.13, cβ=−116.38±0.32 for the spin—rotation interaction of the 31P nucleus, and ζ α=8.01±0.08,ζβ=7.67±0.19 for the spin—rotation interaction of the 1H nuclei. The α constant is the mean interaction in the x and y directions, and the β constant is the interaction about the molecular z axis. No inversion doubling was observed (Δ〈1 kHz). The K=3 levels have K‐doubling fine structure as predicted by Nielson and Dennison, but the magnitude does not agree with their formula.
TL;DR: In this paper, it has been shown that the values of the piezoresistance coefficients depend not only on the surface orientation but also on the magnitude of the gate voltage, and the strongest surface field influence was observed in the (100) plane whereas no gate voltage dependence could be detected on (111) surfaces.
Abstract: Piezoresistance measurements have been carried out on n‐type inversion layers on (100), (110), and (111) silicon at room temperature as a function of the gate voltage (perpendicular electric field). It has been shown that the values of the piezoresistance coefficients depend not only on the surface orientation but also on the magnitude of the gate voltage. The strongest surface field influence was observed in the (100) plane whereas no gate voltage dependence could be detected on (111) surfaces. The data obtained have been interpreted in terms of the quantization of energy levels in inversion layers. This quantization causes generally an occupation anisotropy of the valleys mostly pronounced for an electric field in the [100] direction and disappearing for a [111] direction of the field. Theoretical expressions for the (100) piezoresistance coefficients π11 and π12 have been derived taking into account the field dependences of the population effect and of the intervally scattering contribution, both affec...
TL;DR: In this article, a semi-empirical relation for the zero-field mobility as a function of density was obtained for the high density range studied 1.0-1.4 g/${\mathrm{cm}}^{3}.
Abstract: Drift velocities of electrons in fluid argon have been measured at temperatures from 90 to 160 \ifmmode^\circ\else\textdegree\fi{}K and at pressures from 10 to 100 atm for applied electric fields in the range -25 to -200 V/cm. The electron drift velocity is found to be linear with respect to electric field strength only to -100 V/cm at temperatures from 90 to 125 \ifmmode^\circ\else\textdegree\fi{}K and to become increasingly nonlinear at temperatures greater than 125 \ifmmode^\circ\else\textdegree\fi{}K. Mobilities can be obtained from these data by extrapolation to zero field; maxima are found in the zero-field mobilities as a function of density, in the region of 0.81 g/${\mathrm{cm}}^{3}$. Using the model proposed by Lekner for electron scattering by a system of fluctuating potentials and assuming that the scattering length for electrons in fluid argon approaches zero at some density, it is possible to obtain a semiempirical relation for the zero-field mobility as a function of density. Excellent agreement between calculated and observed mobilities is found in the high-density range studied 1.0-1.4 g/${\mathrm{cm}}^{3}$. At densities less than 1.0 g/${\mathrm{cm}}^{3}$, several qualitative aspects of the experimental data are accounted for by the theory, but quantitative agreement is lacking. It is possible that at these lower densities, gas-like scattering is of dominant importance.
TL;DR: A Nike-Tomahawk rocket equipped to measure electric and magnetic fields and charged particles from a few eV to several hundred keV energy was flown into an auroral band on April 11, 1970 as discussed by the authors.
Abstract: A Nike-Tomahawk rocket equipped to measure electric and magnetic fields and charged particles from a few eV to several hundred keV energy was flown into an auroral band on April 11, 1970 The purpose of this flight was to obtain evidence of the low-energy electrons and protons that constitute a field-aligned sheet current, and also to obtain the magnetic signature of such a current and the electric field in and near the auroral-arc electric current system Particular attention was given to a sudden increase in the field-aligned current associated with a prior sudden increase in the electric field and a sudden change in the magnetic field, all occurring near the edge of a visual auroral arc Data obtained are discussed and analyzed; they present an important contribution to the problem of mapping of atmospheric auroral phenomena to the magnetospheric equatorial plane