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Showing papers on "Electric potential published in 2005"


Journal ArticleDOI
TL;DR: In this article, the authors used a hybrid technique to construct the high-latitude electric potentials and magnetic field aligned currents (FAC) as a function of the solar wind parameters.
Abstract: Improved techniques have been developed for empirical modeling of the high-latitude electric potentials and magnetic field aligned currents (FAC) as a function of the solar wind parameters. The FAC model is constructed using scalar magnetic Euler potentials, and functions as a twin to the electric potential model. The improved models have more accurate field values as well as more accurate boundary locations. Non-linear saturation effects in the solar wind-magnetosphere coupling are also better reproduced. The models are constructed using a hybrid technique, which has spherical harmonic functions only within a small area at the pole. At lower latitudes the potentials are constructed from multiple Fourier series functions of longitude, at discrete latitudinal steps. It is shown that the two models can be used together in order to calculate the total Poynting flux and Joule heating in the ionosphere. An additional model of the ionospheric conductivity is not required in order to obtain the ionospheric currents and Joule heating, as the conductivity variations as a function of the solar inclination are implicitly contained within the FAC model's data. The models outputs are shown for various input conditions, as well as compared with satellite measurements. The calculations of the total Joule heating are compared with results obtained by the inversion of ground-based magnetometer measurements. Like their predecessors, these empirical models should continue to be a useful research and forecast tools.

581 citations


Journal ArticleDOI
TL;DR: In this article, measurements from the Cluster spacecraft of electric fields, magnetic fields, and ions are used to study the structure and dynamics of the reconnection region in the tail at distances of ∼18 RE near 22.4 MLT on 1 October 2001.
Abstract: [1] Measurements from the Cluster spacecraft of electric fields, magnetic fields, and ions are used to study the structure and dynamics of the reconnection region in the tail at distances of ∼18 RE near 22.4 MLT on 1 October 2001. This paper focuses on measurements of the large amplitude normal component of the electric field observed in the ion decoupling region near the reconnection x-line, the structure of the associated potential drops across the current sheet, and the role of the electrostatic potential structure in the ballistic acceleration of ions across the current sheet. The thinnest current sheet observed during this interval was bifurcated into a pair of current sheets and the measured width of the individual current sheet was 60–100 km (3–5 c/ωpe). Coinciding with the pair of thin current sheets is a large-amplitude (±60 mV/m) bipolar electric field structure directed normal to the current sheets toward the midplane of the plasma sheet. The potential drop between the outer boundary of the thin current sheet and the neutral sheet due to this electric field is 4–6 kV. This electric field structure produces a 4–6 kV electric potential well centered on the separatrix region. Measured H+ velocity space distributions obtained inside the current layers provide evidence that the H+ fluids from the northern and southern tail lobes are accelerated into the potential well, producing a pair of counterstreaming, monoenergetic H+ beams. These beams are directed within 20 degrees of the normal direction with energies of 4–6 keV. The data also suggest there is ballistic acceleration of O+ in a similar larger-scale potential well of 10–30 kV spatially coinciding with the larger scale size (∼1000–3000 km) portions of current sheet surrounding the thin current sheet. Distribution functions show counterstreaming O+ populations with energies of ∼20 keV accelerated along the average normal direction within this large-scale potential structure. The normal component of the electric field in the thin current sheet layer is large enough to drive an E × B drift of the electrons ∼10,000 km/s (0.25 x electron Alfven velocity), which can account for the magnitude of the cross-tail current associated with the thin current sheet.

262 citations


Journal ArticleDOI
01 Jul 2005-EPL
TL;DR: A theoretical model for ionic transport through synthetic conical nanopores obtained using the track-etching technique is presented in this paper, based on the Poisson and Nernst-Planck equations.
Abstract: A theoretical model for ionic transport through synthetic conical nanopores obtained using the track-etching technique is presented. The model is based on the Poisson and Nernst-Planck equations. The results provided by the theory are compared with recent experimental current-voltage curves obtained for polymeric membranes containing single, gold-coated conical nanopores. The calculated profiles of average concentration and electric potential along the pore symmetry axis allow for an intuitive explanation of the rectification properties observed in these systems.

253 citations


Journal ArticleDOI
TL;DR: In this paper, the electrohydrodynamic flow in air produced by the electric corona discharge in the pin-plate and pin-grid configurations has been investigated numerically and experimentally.

195 citations


Journal ArticleDOI
TL;DR: In this paper, a linear electroosmotic model based upon the Debye-Huckel theory of the double layer was used to analyze the flow of electrolyte induced by a traveling-wave electric potential applied to an array of microelectrodes.
Abstract: Net flow of electrolyte induced by a traveling-wave electric potential applied to an array of microelectrodes is reported. Two fluid flow regimes have been observed: at small-voltage amplitudes the fluid flow follows the direction of the traveling wave, and at higher-voltage amplitudes the fluid flow is reversed. In both cases, the flow seems to be driven at the level of the electrodes. The experiments have been analyzed with a linear electroosmotic model based upon the Debye–Huckel theory of the double layer. The electrical problem for the experimental interdigitated electrode array is solved numerically using a truncated Fourier series. The observations at low voltages are in qualitative accordance with the electroosmotic model.

182 citations


Journal ArticleDOI
TL;DR: In this paper, single ZnO nanowires are configured as field effect transistors and their electrical properties are characterized using scanning probe microscopy (SPM) to map the electric potential distribution on the nanowire.
Abstract: Single ZnO nanowires are configured as field effect transistors and their electrical properties are characterized using scanning probe microscopy (SPM). Scanning surface potential microscopy is used to map the electric potential distribution on the nanowire. Potential drop along the nanowire and at the contacts are resolved, and contact resistances are estimated. Furthermore, conductive SPM tip is used as a local gate to manipulate the electrical property. The local change of electron density induced by a negatively biased tip significantly affects the current transport through the nanowire.

141 citations


Journal ArticleDOI
TL;DR: In this paper, a method for predicting ground surface geomagnetic variations from measurements of the approaching interplanetary magnetic field (IMF) and solar wind is described, using twin, empirical representations of the ionospheric electric and magnetic Euler potentials' response to the IMF drivers.
Abstract: [1] A technique is described for predicting ground surface geomagnetic variations from measurements of the approaching interplanetary magnetic field (IMF) and solar wind. The method uses twin, empirical representations of the ionospheric electric and magnetic Euler potentials' response to the IMF drivers. The magnetic potential model, originally derived for mapping the large-scale field-aligned current structure, describes the curl-free component of the horizontal ionospheric current, also called the “potential current.” Using approximations that the Hall and Pedersen conductances have a fixed ratio and that there are no conductivity gradients, then the Hall current is derived from the magnetic potentials. In this case the Hall current is the same as the divergence-free “equivalent current,” which is used to derive the geomagnetic variations at the ground surface. The assumption that the ionospheric conductances have no gradients is avoided if the empirical model for the ionospheric electric potentials is used in addition to the magnetic potentials. In this second method the electric field provides additional information about the direction of the estimated equivalent current. Despite the approximation of a fixed conductance ratio, both calculation methods perform remarkably well for predicting the large-scale and long-period geomagnetic variations. The method that includes the electric fields has a slightly better performance, particularly in the polar cap. Corrections for the effects of currents induced underground were not applied for this demonstration. Such corrections could in principle improve the predictions, particularly for the short-period variations for which the effect is the greatest.

116 citations


Journal ArticleDOI
TL;DR: In this paper, the interaction of an ion-collecting sphere at floating potential with a flowing collisionless plasma is investigated using the particle in cell code SCEPTIC, and the dependence of the floating potential on the flow velocity for a conducting sphere is found to agree very well with the orbital motion limited approximation, which ignores the asymmetry in the plasma potential.
Abstract: The interaction of an ion-collecting sphere at floating potential with a flowing collisionless plasma is investigated using the particle in cell code SCEPTIC. The dependence of the floating potential on the flow velocity for a conducting sphere is found to agree very well with the orbital motion limited approximation, which ignores the asymmetry in the plasma potential. But the charge, even on conducting spheres and at zero flow, is not well represented by using the standard expression for capacitance. Insulating spheres become asymmetrically charged because of ion collection asymmetry, and their total (negative) charge is considerably increased by flow. The collection flux asymmetry is documented for both conducting and insulating spheres and is not greatly different between them. The drag force upon the sphere is obtained from the code calculations. It shows reasonable agreement with appropriate analytic approximations. However, numerical discrepancies up to 20% are found, which are attributed to uncertainties in the analytical values.

114 citations


Journal ArticleDOI
TL;DR: In this article, a ring-shaped potential was proposed to solve the Schrodinger equation with the bound states and the exact solutions of the continuous states of the quantum system were derived.

109 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that a charge starved magnetosphere contains significantly less electric current than one with freely available electric charges, and that the magnetosphere may spontaneously rearrange itself to a lower energy configuration through a dramatic release of electromagnetic field energy and magnetic flux.
Abstract: Polar magnetospheric gaps consume a fraction of the electric potential that develops across open field lines. This effect modifies significantly the structure of the axisymmetric pulsar magnetosphere. We present numerical steady-state solutions for various values of the gap potential. We show that a charge starved magnetosphere contains significantly less electric current than one with freely available electric charges. As a result, electromagnetic neutron star braking becomes inefficient. We argue that the magnetosphere may spontaneously rearrange itself to a lower energy configuration through a dramatic release of electromagnetic field energy and magnetic flux. Our results might be relevant in understanding the recent December 27, 2004 burst observed in SGR 1806-20.

94 citations


Journal ArticleDOI
TL;DR: It is demonstrated that additional terms in the analytical expression appearing from derivatives of the approximated Coulomb potential are necessary to provide the gauge-origin independence of the results within a given numerical accuracy.
Abstract: We report the implementation of a method for the calculation of optical rotation. This method is based on the time-dependent density-functional theory and utilizes time-periodic magnetic-field-dependent basis functions. The calculations are based on a density fit. It is demonstrated that additional terms in the analytical expression appearing from derivatives of the approximated Coulomb potential are necessary to provide the gauge-origin independence of the results within a given numerical accuracy. Contributions from these terms also restore the symmetry between the electric and magnetic perturbations in the optical rotation tensor.

Journal ArticleDOI
TL;DR: In this paper, the electrophoretic motion of a conducting particle, driven by an induced-charge mechanism, is analyzed, and the dependence of the motion upon particle shape is embodied in two tensorial coefficients that relate the particle translational and rotational velocities to the externally applied electric field.
Abstract: The electrophoretic motion of a conducting particle, driven by an induced-charge mechanism, is analyzed. The dependence of the motion upon particle shape is embodied in two tensorial coefficients that relate the particle translational and rotational velocities to the externally applied electric field. The coefficients are represented as surface integrals of the electric potential over the particle boundary, thereby eliminating the need to solve the flow field. Nonspherical particles may translate and∕or rotate in response to the imposed field, even if their net electric charge vanishes.

Journal ArticleDOI
TL;DR: In this article, the influence of the magnetic field on the excitation of plasma waves in InGaAs/AlInAs matched high electron mobility transistors is reported, and it is shown that the threshold source-drain voltage of the terahertz emission shifts to higher values under a magnetic field increasing from 0 to 6 T.
Abstract: The influence of the magnetic field on the excitation of plasma waves in InGaAs/AlInAs lattice matched high electron mobility transistors is reported. The threshold source-drain voltage of the excitation of the terahertz emission shifts to higher values under a magnetic field increasing from 0 to 6 T. We show that the main change of the emission threshold in relatively low magnetic fields (smaller than approximately 4 T) is due to the magnetoresistance of the ungated parts of the channel. In higher magnetic fields, the effect of the magnetic field on the gated region of the device becomes important.

Journal ArticleDOI
TL;DR: In this paper, a planar Penning trap is proposed, which provides confinement perpendicular to its plane by an electric potential minimum while a superimposed magnetic field provides radial confinement, and switches between different traps in the planar array allow for controlled interactions between the single stored particles.
Abstract: We present a new concept for a Penning trap, which is planar and allows for the implementation of novel confinement techniques. The trap provides confinement perpendicular to its plane by an electric potential minimum while a superimposed magnetic field provides radial confinement. Both the axial position and the depth of the potential minimum can be controlled by the applied voltages. The device is scalable in the sense that an arbitrary number of planar traps can be embedded in one plane thus representing a multitrap array which can be used for particle interaction studies. Switches between different traps in the planar array allow for controlled interactions between the single stored particles.

Journal ArticleDOI
TL;DR: In this article, the authors presented a model for estimating the trajectory of a natural lightning stroke, including the return-stroke current and very close electric field measurements of the dart-leader charge density.

Journal ArticleDOI
TL;DR: An analytical model to study Joule heating effects on the transport of heat, electricity, momentum and mass species in capillary-based electrophoresis is developed and it is shown that, due to the thermal end effect, sharp temperature drops appear close to capillary ends, where sharp rises of electric field are required to meet the current continuity.

Patent
02 Aug 2005
TL;DR: In this article, an ion mobility spectrometer is described having an ion filter in the form of at least one ion channel having a plurality of electrodes, and a time-varying electric potential applied to the conductive layers allows the filler to selectively admit ion species.
Abstract: An ion mobility spectrometer is described having an ion filter in the form of at least one ion channel having a plurality of electrodes. A time-varying electric potential applied to the conductive layers allows the filler to selectively admit ion species. The electric potential has a drive and a transverse component, and in preferred embodiments each of the electrodes is involved in generating a component of both the drive and transverse fields. The device may be used without a drift gas flow, Microfabrication techniques are described for producing microscale spectrometers, as are various uses of the spectrometer.

Journal ArticleDOI
TL;DR: In this article, the exact solution for the simply supported and multilayered magneto-electro-thermoelastic strip under a plane strain state was obtained for a three-layered composite strip constructed of piezoelectric and magnetostrictive materials.

Journal ArticleDOI
07 Apr 2005-Langmuir
TL;DR: An additional degree of freedom is introduced for the surface deformation, the surface stretch, to account for the observation of a reversible normal relaxation of the top atomic layer as a function of the electrochemical potential.
Abstract: We analyze the simultaneous mechanical and chemical equilibrium at the interface between a fluid electrolyte and a solid conductor in terms of a continuum theory, with attention to surfaces of varying orientation and of arbitrary curvature. On top of the variable which is conjugate to the surface stress, the tangential strain, we introduce an additional degree of freedom for the surface deformation, the surface stretch, to account for the observation of a reversible normal relaxation of the top atomic layer as a function of the electrochemical potential. We derive relations between the materials constants of the surface, for instance, the pressure dependence of the electric potential at constant superficial charge density, and discuss experiments-using cantilevers or porous solids-by which they can be measured.

Journal ArticleDOI
TL;DR: In this article, a class of accurate and reliable piezoelectric plate elements is presented based upon the Reissner-Mindlin assumptions, which makes the elements applicable to both thin and moderately thick situations.

Journal ArticleDOI
TL;DR: Density-functional studies of the recently fabricated, lattice-matched perovskite titanates (SrTiO3)n/(LaTiO 3)m reveal a classic wedge-shaped potential well for the monolayer structure, originating from the Coulomb potential of a two-dimensional charged La sheet.
Abstract: Oxide superlattices and microstructures hold the promise for creating a new class of devices with unprecedented functionalities. Density-functional studies of the recently fabricated, lattice-matched perovskite titanates (SrTiO3)n/(LaTiO3)m reveal a classic wedge-shaped potential well for the monolayer (m = 1) structure, originating from the Coulomb potential of a two-dimensional charged La sheet. The potential in turn confines the electrons in the Airy-function-localized states. Magnetism is suppressed for the monolayer structure, while in structures with a thicker LaTiO3 part, bulk antiferromagnetism is recovered, with a narrow transition region separating the magnetic LaTiO3 and the nonmagnetic SrTiO3.

Journal ArticleDOI
TL;DR: In this article, the magnetic mirror effect is studied in the channel of a Hall thruster and it is shown that gradients in magnetic field affect the presheath structure and electric potential distribution.
Abstract: The magnetic mirror effect is studied in the channel of a Hall thruster It is shown that gradients in magnetic field affect the presheath structure and electric potential distribution The length of the radial presheath region decreases in the presence of a magnetic field gradient The two-dimensional potential shape can be affected by proper choice of the magnetic mirror ratio In particular, it is possible to obtain a concave shape of the potential profile in the channel even in the case of a primarily radial magnetic field This, in turn, can be used to efficiently control the ion dynamics in the acceleration region

Journal ArticleDOI
TL;DR: In this paper, the radial electric field profiles of the effective helical ripples are controlled by the modification of the magnetic field by changing the radial profile of the ripples,?h, creating a magnetic island with an external perturbation field coil and changing the local island divertor coil current.
Abstract: Control of the radial electric field, Er, is considered to be important in helical plasmas, because the radial electric field and its shear are expected to reduce neoclassical and anomalous transport, respectively. In general, the radial electric field can be controlled by changing the collisionality, and positive or negative electric fields have been obtained by decreasing or increasing the electron density, respectively. Although the sign of the radial electric field can be controlled by changing the collisionality, modification of the magnetic field is required to achieve further control of the radial electric field, especially to produce a strong radial electric field shear. In the Large Helical Device (LHD) the radial electric field profiles are shown to be controlled by the modification of the magnetic field by (1) changing the radial profile of the effective helical ripples, ?h, (2) creating a magnetic island with an external perturbation field coil and (3) changing the local island divertor coil current.

Journal ArticleDOI
TL;DR: In this paper, the three-dimensional non-hydrostatic mesoscale model MesoNH of the French community offers the numerical environment to develop a cloud electrification scheme in a consistent way with the original mixed phase microphysical scheme.

Journal ArticleDOI
TL;DR: In this paper, the authors solved the continuity equations governing electron and ion density with Poisson's equation to obtain spatial and temporal profiles of electron density, ion density, and voltage, and obtained the value of charge separation e(ni−ne) and the force per volume F=e(ni −ne)E near the dielectric surface for the 50th cycle.
Abstract: Continuity equations governing electron and ion density are solved with Poisson’s equation to obtain spatial and temporal profiles of electron density, ion density, and voltage. The motion of electrons and ions results in charge separation and generation of an electrostatic electric field. Electron deposition downstream of the overlap region of the electrode results in formation of a virtual negative electrode that always attracts the charge separation. The value of charge separation e(ni−ne) and the force per volume F=e(ni−ne)E have been obtained near the dielectric surface for the 50th cycle. Domain integration of the force F=e(ni−ne)E has been obtained for different plasma densities, frequencies, and rf voltage wave forms. The time average of the x force is positive and the y force is negative over the domain; therefore there is an average net force on the plasma in the positive x and negative y directions. This will result in a moving wave of plasma over the dielectric surface in the positive x direct...

Journal ArticleDOI
TL;DR: In this paper, the potential and electric field distributions along a typical ceramic extremely highvoltage post insulator covered with atmospheric ice during a melting period were determined using the boundary element method (BEM).
Abstract: The main objective of this paper is to determine the potential and electric-field distributions along a typical ceramic extremely-high-voltage post insulator covered with atmospheric ice during a melting period. Commercial software, Coulomb 3D, based on the boundary element method (BEM), was used for all of the three-dimensional modeling and simulations. It was demonstrated that the BEM is well suited for evaluating the effect of ice shedding on the potential and electric-field distributions along an ice-covered insulator during a melting period. The results obtained show that the length and number of ice free zones, also called air gaps, are the major parameters that affect the applied voltage distribution along an ice-covered insulator. The mean electric field per arcing distance, affected mainly by the air-gap lengths, can provide a good indication of the presence of partial arcing along the different air gaps.

Journal ArticleDOI
TL;DR: In this article, the effect of both an electric and magnetic field on the hydrogenic binding energy of a shallow donor impurity in a coaxial GaAs-(Ga, Al)As quantum well wire (QWW) has been investigated as a function of the impurity position and barrier thicknesses for different values of the applied magnetic and electric field strengths.
Abstract: The effect of both an electric and magnetic field on the hydrogenic binding energy of a shallow donor impurity in a coaxial GaAs-(Ga, Al)As quantum well wire (QWW) has been investigated as a function of the impurity position and barrier thicknesses for different values of the applied magnetic and electric field strengths. Within the effective mass approximation, the ground-state energy in the presence of a uniform magnetic field applied parallel to the wire axis has been calculated using the fourth-order Runge–Kutta method. The ground state binding energy under applied electric field has been studied with a variational approach. The two sharp increase in the binding energy have observed for the donor impurity located at outside of the center under the critical electric and magnetic field values. However, for the electric field off the binding energy monotonously decrease with increasing magnetic field strength up to a critical magnetic field and then a sharp decrease is seen before reaching a constant value. For the impurity located at the center, the abrupt deviations of the binding energy strongly depend not only on the electronic confinement, but also on the electric and magnetic field strength. We expect that these results will be useful in technological applications.

Journal ArticleDOI
TL;DR: In this article, a Coulomb gauge condition was proposed to improve the convergence behavior of the electric vector potential for static three-dimensional fully coupled electromechanical problems, and a penalized version of the weak vector potential formulation was proposed and tested on some numerical examples in electrostatics and piezoelectricity.
Abstract: A vector potential for the electric induction is applied to static three-dimensional fully coupled electromechanical problems. A Coulomb gauge condition imposed on the electric vector potential improves the convergence behaviour of nonlinear problems, and in combination with a discrete set of Dirichlet boundary conditions, it can enforce unique vector potential solutions. Based on a spectral analysis of the stiffness matrix, the Coulomb gauge is compared with other gauge conditions. A penalized version of the weak vector potential formulation with Coulomb gauge is proposed and tested on some numerical examples in electrostatics, piezoelectricity and ferroelectricity. Copyright © 2005 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, an analytical method to solve thermo-electro-elastic transient response in piezoelectric hollow structures subjected to arbitrary thermal shock, sudden mechanical load and electric excitation is presented.

Proceedings ArticleDOI
23 May 2005
TL;DR: The charge redistribution loss of capacitors is reviewed, and then employed in the optimal capacitor assignment of charge pumps, and the average output voltage is unambiguously defined.
Abstract: The charge redistribution loss of capacitors is reviewed, and then employed in the optimal capacitor assignment of charge pumps. The average output voltage is unambiguously defined, and efficiency due to redistribution loss is discussed. Analyses are confirmed by Hspice simulations on charge pumps designed using a 0.35 /spl mu/m CMOS process.