Showing papers on "Electric potential published in 1978"

A double layer review

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.

Solution of the Smoluchowski equation with a Coulomb potential. I. General results

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.

Discrete Variational Xα Cluster Calculations. II. Application to the Surface Electronic Structure of MgO

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.

A model of the magnetospheric electric convection field

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).

EHD study of the corona wind between wire and plate electrodes

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.

Electrokinetic and magnetic anomalies associated with dilatant regions in a layered Earth

Abstract: According to the dilatancy-diffusion earthquake model, there will be fluid motion into a dilatant zone prior to an earthquake. One possible consequence of this fluid motion is the generation of an electric potential anomaly by means of electrokinetic processes. A surface electric potential anomaly will not be produced unless there is a boundary separating regions of differing streaming potential coefficient and there is a component of pressure gradient parallel to this boundary. The magnetic anomaly produced by the current flow is calculated. It is shown for the case of an n-layered half space that the surface magnetic field will be identically zero no matter what the pressure distribution is. There will, however, be an azimuthal component of the magnetic field inside the earth.

The ambipolarity paradox in toroidal diffusion, revisited

Abstract: The radial current in an axisymmetric toroidal plasma is shown to damp away because of parallel ion viscosity on the ion-ion collision time scale. After this transient phase, the electrostatic potential is quasi-statically related to the toroidal angular momentum of each flux surface, and the cross-field particle fluxes are ambipolar and independent of the radial electric field.

Potential drops above pulsar polar caps - Ultrarelativistic particle acceleration along the curved magnetic field

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.

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.

Solution of the time‐dependent Onsager problem

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...

Experimental observations of strong double layers

Abstract: A computer simulation is applied to the production of strong electric potential double layers (DL) in a triple plasma device. The simulation is intended to represent DL in the low magnetosphere above the auroral zones. The DL are described as standing electrostatic shocks with different energy coefficients in their strong and weak forms. The strong DL was generally found to be unstable, but stability could be imparted if a population of trapped electrons was presented. Stability increased with the length of the system. A schematic for the system is presented, and a phase-space plot of electrons (indicating system stability) is graphed.

Magnetic field‐aligned potential drops due to electrostatic ion cyclotron turbulence

Abstract: Measurements of DC and AC electric fields and plasma densities on the S3-3 satellite have shown that electrostatic ion cyclotron (EIC) turbulence is associated with significant DC electric fields parallel to auroral field lines The EIC mode has been identified in regions of strong DC electric fields and magnetic field aligned currents by AC electric field and density fluctuations with frequency components between the local hydrogen gyrofrequency and its harmonics, and by wave vector polarization primarily perpendicular to the magnetic field at wavelengths of an ion gyroradius The anomalous resistivity has been computed for measured AC electric fields of 50 mV/m in the EIC mode, yielding approx1 mV/m DC parallel electric fields for measured currents of approx10 muA/m/sup 2/ This theoretical results implies that several kV potential drops will occur if the anomalous resistivity region extends over several thousand kilometers along auroral field lines This is adequate to accelerate auroral particles to observed energies and consistent with the scale height over which parallel electric fields and EIC turbulence are statistically observed on S3-3

Point charge in a three‐dielectric medium with planar interfaces

Abstract: A simple method of obtaining integral representations of the electrostatic potential, the induced surface charge density, and the image potential for a point charge in a three‐dielectric medium with infinite planar interfaces is presented. The total induced charge at the interfaces is readily evaluated. Numerical results for the image potential in several illustrative cases are also shown. The case of a point charge between two grounded conducting plates becomes a special limiting case of the present problem.

Static electric potential structures on the surface of a type II superconductor in the flux flow state

Abstract: The static electric potential on the surface of a reversible type II superconducting cylinder carrying a current in an axial field has been investigated as a continuous function of position using a fine sliding contact. Three distinct regions of behaviour are identified, at low, medium and high applied axial fields. The remarkable potential structures displaying negative field regions, which were inferred by Irie, Ezaki and Yamafuji (1974) from point contact measurements, have been traced directly with a resolution of 50 μm. The voltage structure is shown to be very stable and reproducible with a complex fine structure. It is more irregular than supposed by Irie et al. (1974); the negative field regions are narrower and the traces do not appear to be strictly periodic, although there is some evidence that certain features of the traces repeat at regular intervals.

Lorentz invariance of the quantum field theory of electric and magnetic charge

Abstract: The Lorentz invariance of the gauge-invariant Green's functions in the local quantum field theory of electric and magnetic monopoles is formally established. This is accomplished by expressing these Green's functions as functional integrals over the trajectories of classical charged particles.

E1-M1 Interference in Radiative Decay of Hydrogenlike Atoms in an Electric Field

Abstract: An unpolarized hydrogenlike atom in the metastable $2{S}_{\frac{1}{2}}$ state in an electric field decays primarily by one- or two-photon emission. The angular distribution of the single-photon radiation is expected to be asymmetric with respect to the electric field direction as a result of $E1\ensuremath{-}M1$ interference. Observable consequences of this effect in high-$Z$ Lamb-shift experiments in progress are pointed out. A lowest-order estimate is given for the dependence of the asymmetry on the nuclear charge and the applied field strength.

Ionisation of highly-excited atoms by electric fields. I. Classical theory of the critical electric field for hydrogenic ions

Abstract: An exact classical method is developed for the study of the critical ionisation of highly-excited hydrogenic ions by slowly varying applied electric fields, under the assumption of adiabatic invariance of the classical action integrals. Exact classical values of the critical field, the critical energy of the atom and the separation constant are determined for a wide range of values of the parabolic action integrals. Simple analytic fits accurate to within one per cent of these values are presented. For applications to real atoms, effects of tunnelling and level crossing must be included. Corrections are also required for low-l states of excited non-hydrogenic atoms and ions.

The energy and electron density of states of H in Pd, Rh and Ni

Abstract: The authors introduce a new model for the screened Coulomb potential appropriate to dilute interstitial hydrogen impurities in a metallic host. This new potential provides an accurate representation of the self-consistent potential of a proton in an electron gas and is more suitable than the customary Thomas-Fermi potential in that it yields a charge density which is finite at the impurity site. Calculations have been performed using this new potential and the screened Coulomb potential employed in earlier work, for the case of hydrogen in palladium. Neither the change in the electronic structure, Delta N(E), nor the change in the total energy, Delta E, are found to be very dependent on the exact form of the screened Coulomb potential. The theoretical formalism has also been extended to the case of dilute hydrogen interstitial impurities in the FCC transition metals Ni and Rh. In both metals Delta E is found to be approximately -1.1 Ryd, and the octahedral site is predicted to have lower energy in agreement with experiment.

The Zero-Range Potential Model and Its Application in Atomic and Molecular Physics

Abstract: Publisher Summary This chapter discusses the zero-range potential model (ZRPM) and its application in atomic and molecular physics. The ZRPM is a method of treating the problem of a particle in the field of a short-range potential well when there is a shallow energy level near the boundary of the continuum spectrum. The basic idea of ZRPM is to replace the Schrodinger equation inside the well by a certain boundary condition on the wavefunction at the center of the well. The ZRPM can be easily generalized for the case when there are several potential wells at rest or moving and also when, besides the wells, there are electric and magnetic fields. The chapter also discusses the basic relations and presents some applications of one- and many-center boundary conditions in atomic and molecular physics. A charged particle was studied under the action of (1) a homogeneous electric field, (2) a homogeneous magnetic field, (3) crossed electric and magnetic fields, (4) a rotating electric field, and (5) a Coulomb field of a point charge.

Electric Fields in Dielectric Multi-Layers Calculated by Digital Computer

Abstract: The electric field of a point charge or a spherical conductor in three or more dielectric layers on a plane conductor is calculated ated by digital computer. That of a point charge is calculated by the method of images, and that of a spherical conductor by the charge simulation method in combination with the method of images. Numerical examples show that the potential, the field strength, and the flux density, all satisfy the boundary conditions with good accuracy. The method can be applied to fields of a line charge, a pillar conductor, and an electrode of body of revolution in the same circumstance.

A hydromagnetic dynamo of the atmosphere

Abstract: Conventional dynamo theories start from wind fields which are considered as external forces independent of the ionospheric plasma. These dynamos are called kinematic dynamos. Coupling between the neutral wind and the ionospheric plasma in a self-consistent manner results in a hydromagnetic dynamo. In this paper a theory of a hydromagnetic dynamo of the geomagnetic Sq current is developed assuming a thin shell model with constant elements of the electric conductivity tensor. Coupling between neutral gas and plasma is described by the Ampere force j × Bo (j being electric current density and Bo geomagnetic field) which depends not only on the velocity difference between neutrals and plasma (ion drag) but also on the electric polarization field. The electric polarization field includes a source free component which is not negligibly small at dynamo layer heights, so that the electric field cannot be represented by an electric potential. This theory leads to a modified Laplace equation of tidal theory which can be solved numerically. Calculations are presented for the diurnal and the semidiurnal tidal wave modes. Their equivallent depths, their vertical wavelengths, and their attenuation factors are discussed as functions of a plasma parameter δ which is proportional to a Cowling conductivity. The horizontal structures of pressure and electric current of the dominant symmetric tidal waves are determined for different values of δ representing the lower atmosphere (δ = 0), the dynamo region (δ ≃ 1), and F layer heights (δ ≃ 10). It is shown that waves with positive equivalent depths at δ = 0 are heavily attenuated at δ > 1 and drastically change their horizontal structure there. On the other hand, waves with negative equivalent depths at δ = 0 are only weakly affected by the Ampere force. From our calculations we suggest that tidal wave theory at thermospheric heights should be reconsidered taking into account electric coupling between the modes. In particular, we predict that the semidiurnal (2, 2) wave so far considered as the dominant semidiurnal mode above about 200 km height may have lost its significance and may in fact be replaced by the symmetric (2, -3) wave.

Electric energy density in a dissipative medium by circuit analog

Abstract: In a dispersive and dissipative medium, the electric energy density is no longer given by (1/2)E⋅D. When the dielectric function is given, the electric energy density of a monochromatic wave can be calculated by considering the energy stored in an equivalent linear circuit.

Beam generation in foil‐less diodes

Abstract: A study is made of the generation of intense relativistic electron beams in rectangular and cylindrical foil‐less diodes. The diode space charge is treated self‐consistently. The electron emission from the cathode is assumed to be space‐charge‐limited. A strong axial magnetic field is assumed to prevent the electrons from reaching the anode surface(s) directly, and to constrain the electron motion to be approximately one‐dimensional. A useful dimensionless measure of the diode potential φc is e≈[mec2/(eφc)]1/2, with me and e the electron rest mass and charge, and c the speed of light. Properties of the diodes are first analyzed in the ultra‐relativistic limit, e=0, where the condition for space‐charge‐limited emission gives rise to a linear singular integral equation. This equation is solved for rectangular diode geometry, and the solutions are studied in detail. In particular, the diode impedance is independent of φc, and the beams are, in general, hollow. The beam particle kinetic energy flux, Γp, decre...