scholarly journals Radio emission from polar caps in pulsars

1996 ◽  
Vol 160 ◽  
pp. 181-182
Author(s):  
Jan Kuijpers ◽  
Martin Volwerk
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Resonance Condition ◽  
Linear Acceleration ◽  
Stellar Atmospheres ◽  
Double Layers ◽  
Radio Pulsars ◽  
Polar Caps ◽  
Particle Speed ◽  
A Charge

Radiation from a charge accelerated along its path or Linear Acceleration Emission (LAE) involves a number of subtleties (Pauli 1921; Ginzburg 1970, 1989). Potential interest of the mechanism for astrophysics has been pointed out by Wagoner (1969). Melrose (1978) and Rowe (1995) have studied amplified LAE from time-varying electric fields for radio pulsars. In contrast with the latter work our calculations are for static electric field structures or double layers (DLs) as are thought to occur in magnetospheres of neutron stars. In ordinary stellar atmospheres a LAE maser can operate in non-relativistic DLs (Kuijpers 1990) at a frequencyω≈kDLυ≈ 2π/ttr, and a wave vectorwithkDL= 2π/L(Lis the DL length,υis the particle speed, andttris the transit time of the DL by the particle). The emission process can be considered as scattering of the electrostatic electric field on fast electrons into electromagnetic radiation satisfying the resonance condition:, when the frequency of the radiated mode in the frame of the emitting electron equals the Doppler shifted frequency of the electric field of the DL (DL wave frequencyωDL≈ 0). For relativistic DLs, as are applicable to pulsar magnetospheres, the emission is expected to be beamed under an angleθ≈γ−1and the frequency of emission boosted (ω≈kDLυ(1 −υcosθ/c)−1≈γ2kDLυ).

scholarly journals Double layers in the downward current region of the aurora

2003 ◽  
Vol 10 (1/2) ◽  
pp. 45-52 ◽  
Author(s):  
R. E. Ergun ◽  
L. Andersson ◽  
C. W. Carlson ◽  
D. L. Newman ◽  
M. V. Goldman
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Phase Space ◽  
Electric Field ◽  
Electric Fields ◽  
Double Layers ◽  
Parallel Electric Field ◽  
Electrostatic Waves ◽  
Current Region ◽  
Decisive Evidence

Abstract. Direct observations of magnetic-field-aligned (parallel) electric fields in the downward current region of the aurora provide decisive evidence of naturally occurring double layers. We report measurements of parallel electric fields, electron fluxes and ion fluxes related to double layers that are responsible for particle acceleration. The observations suggest that parallel electric fields organize into a structure of three distinct, narrowly-confined regions along the magnetic field (B). In the "ramp" region, the measured parallel electric field forms a nearly-monotonic potential ramp that is localized to ~ 10 Debye lengths along B. The ramp is moving parallel to B at the ion acoustic speed (vs) and in the same direction as the accelerated electrons. On the high-potential side of the ramp, in the "beam" region, an unstable electron beam is seen for roughly another 10 Debye lengths along B. The electron beam is rapidly stabilized by intense electrostatic waves and nonlinear structures interpreted as electron phase-space holes. The "wave" region is physically separated from the ramp by the beam region. Numerical simulations reproduce a similar ramp structure, beam region, electrostatic turbulence region and plasma characteristics as seen in the observations. These results suggest that large double layers can account for the parallel electric field in the downward current region and that intense electrostatic turbulence rapidly stabilizes the accelerated electron distributions. These results also demonstrate that parallel electric fields are directly associated with the generation of large-amplitude electron phase-space holes and plasma waves.

The vibration of electrified water drops

1971 ◽  
Vol 322 (1551) ◽  
pp. 523-534 ◽  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Axial Ratio ◽  
Uniform Electric Field ◽  
Interferometric Technique ◽  
Photographic Analysis ◽  
Wide Range ◽  
Water Drops ◽  
Strength And Deformation ◽  
A Charge

Pressure has been used as the principal parameter in calculations of the fundamental vibrational frequencies of spherical drops of radius R , density ρ, and surface tension T carrying a charge Q or uncharged spheroidal drops of axial ratio a / b situated in a uniform electric field of strength E . Freely vibrating charged drops have a frequency f = f 0 ( 1 - Q 2 /16π R 3 T ) ½ , as shown previously by Rayleigh (1882) using energy considerations; f 0 is the vibrational frequency of non-electrified drops (Rayleigh 1879). The fundamental frequency of an uncharged drop in an electric field will decrease with increasing field strength and deformation a / b and will equal zero when E ( R )/ T ) ½ = 1.625 and a / b = 1.86; these critical values correspond to the disintegration conditions derived by Taylor (1964). An interferometric technique involving a laser confirmed the accuracy of the calculations concerned with charged drops. The vibration of water drops of radius around 2 mm was studied over a wide range of temperatures as they fell through electric fields either by suspending them in a vertical wind tunnel or allowing them to fall between a pair of vertical electrodes. Photographic analysis of the vibrations revealed good agreement between theory and experiment over the entire range of conditions studied even though the larger drops were not accurately spheroidal and the amplitude of the vibrations was large.

scholarly journals Charge Densities above Pulsar Polar Caps

2000 ◽  
Vol 177 ◽  
pp. 463-464
Author(s):  
A. Jessner ◽  
H. Lesch ◽  
Th. Kunzl
Keyword(s):  
Neutron Star ◽  
Electric Field ◽  
Work Function ◽  
Potential Barrier ◽  
Electric Fields ◽  
Surface Potential ◽  
Thermal Emission ◽  
Equilibrium Density ◽  
Charge Densities ◽  
Polar Caps

A simplified model provided the framework for our investigation into the distribution of energy and charge densities above the polar caps of a rotating neutron star. We assumed a neutron star withm= 1.4M⊙,r= 10km, dipolar field |B0| = 1012G,B||Ω and Ω = 2Π · (0.5s)−1. The effects of general relativity were disregarded. The induced accelerating electric fieldE||reachesE0= 2.5 · 1013V m−1at the surface near the magnetic poles. The current density along the field lines has an upper limitnGJ, when the electric field of the charged particle flow cancels the induced electric field: At the polesnGJ(r=rns,θ= 0) = 1.4 · 1017m−3.The work function(surface potential barrier)EWis approximated by the Fermi energyEFof magnetised matter. Following Abrahams and Shapiro (1992) one needs to revise the surface density from the canonical 1.4 · 108kg m−3down toρFe = 2.9 · 107kg m−3. Withwe obtain a value ofEF=Ew= 417eV. There are two relevant particle emission processes:Field (cold cathode) emissionby quantum-mechanical tunneling of charges through the surface potentialandthermal emissionwhich is a purely classical process. In strong electric fields it is enhanced by the lowering of the potential barrier due to the Schottky effect. The combined Dushman-Schottky equationwithtells us, thatat temperatures> 2 · 105K the the Goldreich-Julian current can be supplied thermal emission alone. The surface temperature however has a lower limit in the order of 105K due to the rotational braking. Therefore, in most cases a sufficient supply of charges for the Goldreich-Julian current is available and the electrical field accelerating the particles will be quenched as a result of their abundance. Otherwise a residual equilibrium electric field Eeqremains with:and hence the equilibrium density is:n=nfieid(Eeq,EW) +nDS(Eeq,EW,T) For a temperature just below the onset of thermal emission (T= 1.85 · 105K) the charge density is found to vary almost linearly with the work functionEWfor values ofEWbetween 0.3 and 2 keV. At the chosen value forEWof 417 eVthe residual electric field amounts to only 8.5% of the vacuum value. Even in the residual electric field the particles are rapidly accelerated to relativistic energies balanced by inverse Compton and curvature radiation losses.

scholarly journals Photo- and electroluminescence of oxide-nitride-oxide-silicon structures for silicon-based optoelectronics

2018 ◽  
Vol 62 (5) ◽  
pp. 546-554
Author(s):  
I. A. Romanov ◽  
L. A. Vlasukova ◽  
F. F. Komarov ◽  
I. N. Parkhomenko ◽  
N. S. Kovalchuk ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Silicon Oxide ◽  
Light Emission ◽  
Chemical Vapor ◽  
Nitride Layer ◽  
Silicon Oxynitride ◽  
Radiative Relaxation ◽  
A Charge ◽  
Nitride Oxide

Oxide-nitride-oxide-silicon (SiO2/SiN0.9/SiO2/Si) structures have been fabricated by chemical vapor deposition. The elemental composition and light emission properties of “SiO2/SiN0.9/SiO2/Si” structures have been studied using Rutherford backscattering spectroscopy (RBS), photo- and electroluminescence (Pl, El). The RBS measurements has shown the presence of an intermediate silicon oxynitride layers at the SiO2–SiN0.9 interfaces.It has been shown that the photoluminescence of the SiO2/SiN0.9/SiO2/Si structure is due to the emission of a SiN0.9 layer, and the electroluminescence is attributed to the emission of silicon oxide and oxynitride layers. A broad intense band with a maximum at 1.9 eV dominates the Pl spectrum. This band attributed to the radiative recombination of excited carriers between the band tail states of the SiN0.9 layer. The origin of the less intense Pl band at 2.8 eV is associated with the presence  of nitrogen defects in the silicon nitride.El was excited in the electrolyte-dielectric-semiconductor system. The electric field strength in the SiO2 layers reached 7–8 MV/cm and exceeded this parameter in nitride layer nearly four times. The electrons accelerating in electric field of 7–8 MV/cm could heat up to energies more than 5 eV. It is sufficient for the excitation of luminescence centres in the silicon oxide and oxynitride layers. The SiO2/SiN0.9/SiO2/Si composition El bands with quantum energies of 1.9 and 2.3 eV are related to the presence of silanol groups (Si–OH) and three-coordinated silicon atoms (≡Si•) in the silicon oxide layers. The El band with an energy of 2.7 eV is attributed to the radiative relaxation of silylene (O2=Si:) centers in the silicon oxynitride regions. It is observed the least reduction of this band intensity under the influence of strong electric fields after a charge flow  of 1–3 C/cm2.

scholarly journals Storm enhanced density: magnetic conjugacy effects

2007 ◽  
Vol 25 (8) ◽  
pp. 1791-1799 ◽  
Author(s):  
J. C. Foster ◽  
W. Rideout
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Ionospheric Disturbance ◽  
Polar Regions ◽  
The North ◽  
Polar Caps ◽  
Source Regions ◽  
Field Lines ◽  
Magnetic Conjugacy ◽  
Early Phases

Abstract. In the early phases of a geomagnetic storm, the low and mid-latitude ionosphere are greatly perturbed. Large SAPS electric fields map earthward from the perturbed ring current overlapping and eroding the outer plasmasphere and mid-latitude ionosphere, drawing out extended plumes of storm enhanced density (SED). We use combined satellite and ground-based observations to investigate the degree of magnetic conjugacy associated with specific features of the stormtime ionospheric perturbation. We find that many ionospheric disturbance features exhibit degrees of magnetic conjugacy and simultaneity which implicate the workings of electric fields. TEC enhancements on inner-magnetospheric field lines at the base of the SED plumes exhibit localized and longitude-dependent features which are not strictly magnetic conjugate. The SED plumes streaming away from these source regions closely follow magnetic conjugate paths. SED plumes can be used as a tracer of the location and strength of disturbance electric fields. The SED streams of cold plasma from lower latitudes enter the polar caps near noon, forming conjugate tongues of ionization over the polar regions. SED plumes exhibit close magnetic conjugacy, confirming that SED is a convection electric field dominated effect. Several conclusions are reached: 1) The SED plume occurs in magnetically-conjugate regions in both hemispheres. 2) The position of the sharp poleward edge of the SED plume is closely conjugate. 3) The SAPS electric field is observed in magnetically conjugate regions (SAPS channel). 4) The strong TEC enhancement at the base of the SED plume in the north American sector is more extensive than in its magnetic conjugate region. 5) The entry of the SED plume into the polar cap near noon, forming the polar tongue of ionization (TOI), is seen in both hemispheres in magnetically-conjugate regions.

Characterization of interactive force acting on colloidal particles near an electrode in presence of a high-frequency (>10 kHz) AC electric field using particle diffusometry

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Kshitiz Gupta ◽  
Dong Hoon Lee ◽  
Steven T. Wereley ◽  
Stuart J. Williams
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Particle Motion ◽  
Electrode Surface ◽  
High Frequency ◽  
Colloidal Particles ◽  
Low Frequency ◽  
Double Layers ◽  
Average Height ◽  
Ac Electric Field

Colloidal particles like polystyrene beads and metallic micro and nanoparticles are known to assemble in crystal-like structures near an electrode surface under both DC and AC electric fields. Various studies have shown that this self-assembly is governed by a balance between an attractive electrohydrodynamic (EHD) force and an induced dipole-dipole repulsion (Trau et al., 1997). The EHD force originates from electrolyte flow caused by interaction between the electric field and the polarized double layers of both the particles and the electrode surface. The particles are found to either aggregate or repel from each other on application of electric field depending on the mobility of the ions in the electrolyte (Woehl et al., 2014). The particle motion in the electrode plane is studied well under various conditions however, not as many references are available in the literature that discuss the effects of the AC electric field on their out-of-plane motion, especially at high frequencies (>10 kHz). Haughey and Earnshaw (1998), and Fagan et al. (2005) have studied the particle motion perpendicular to the electrode plane and their average height from the electrode mostly in presence of DC or low frequency AC (<1 kHz) electric field. However, these studies do not provide enough insight towards the effects of high frequency (>10 kHz) electric field on the particles’ motion perpendicular to the electrode plane.  

Cotton as an Electret

1977 ◽  
Vol 47 (7) ◽  
pp. 471-476 ◽  
Author(s):  
Louis C. Weiss ◽  
Devron P. Thibodeaux
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Elevated Temperatures ◽  
Cotton Fibers ◽  
Threshold Values ◽  
Charge Density Distribution ◽  
Polyester Fibers ◽  
A Charge ◽  
Temperature Time

Research to enhance the storage of electrical charge in lint cotton led to imparting electret-like properties to cotton fibers. An electrostatic field introduced stored, oriented charges within a bundle of cotton fibers. The threshold values of temperature, time, and electric field for production of cotton electrets are defined, and specifications for measuring charge-density distribution are presented. The electret nature of the phenomenon is substantiated by findings that cotton fibers exposed to electric fields at elevated temperatures show long-term, charge-retention properties that are enhanced by short-circuiting. These fibers also display a tendency to a charge-polarity reversal after being removed from the electric field. Furthermore, the waxes native to the single fiber seem to be the basis of this new cotton property. These waxes are related to one of the best known electret materials—carnauba wax. A similar effect with analogous characteristics has also been produced in polyester fibers. With both fibers the effect is less than that possessed by ideal electrets.

scholarly journals Extreme electric fields power catalysis in the active site of ketosteroid isomerase

Science ◽  
2014 ◽  
Vol 346 (6216) ◽  
pp. 1510-1514 ◽  
Author(s):  
Stephen D. Fried ◽  
Sayan Bagchi ◽  
Steven G. Boxer
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Active Site ◽  
Stark Effect ◽  
Catalytic Effect ◽  
Biomolecular Systems ◽  
Ketosteroid Isomerase ◽  
Rate Determining Step ◽  
Experimental Approaches ◽  
A Charge

Enzymes use protein architecture to impose specific electrostatic fields onto their bound substrates, but the magnitude and catalytic effect of these electric fields have proven difficult to quantify with standard experimental approaches. Using vibrational Stark effect spectroscopy, we found that the active site of the enzyme ketosteroid isomerase (KSI) exerts an extremely large electric field onto the C=O chemical bond that undergoes a charge rearrangement in KSI’s rate-determining step. Moreover, we found that the magnitude of the electric field exerted by the active site strongly correlates with the enzyme’s catalytic rate enhancement, enabling us to quantify the fraction of the catalytic effect that is electrostatic in origin. The measurements described here may help explain the role of electrostatics in many other enzymes and biomolecular systems.

Electric Field Enhancement of Dark Current Generation in Detectors

2004 ◽  
Vol 829 ◽  
Author(s):  
James P. Lavine
Keyword(s):  
Activation Energy ◽  
Electric Field ◽  
Electric Fields ◽  
Dark Current ◽  
Field Enhancement ◽  
Electric Field Enhancement ◽  
Current Generation ◽  
Field Relation ◽  
Defects And Impurities ◽  
A Charge

ABSTRACTThe performance of detectors and sensors is degraded by dark current generation, which is due to defects and impurities in the materials. Electric fields enhance the generation from the resulting deep levels. When the electric field is in the mid-105 V/cm range, the present work finds enhancements of the order of 100 or more for iron and gold in silicon. The activation energy of the generation rate as a function of temperature is seen to decrease when the electric field increases. Many detectors have pixels that form a charge packet before the detectors are read out. Since the presence of charge decreases the electric field, the electric field enhancement varies with time. This is modeled for iron in silicon with an illustrative charge versus electric field relation. The resulting activation energy is found to be barely affected.

scholarly journals The path of an electron in combined radial magnetic and electric fields

1911 ◽  
Vol 85 (578) ◽  
pp. 257-262 ◽  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Electric Fields ◽  
Circular Cone ◽  
Conic Section ◽  
Magnetic Pole ◽  
Actual Distribution ◽  
A Charge ◽  
The Magnetic Field ◽  
Lines Of Force

1. In the course of an investigation with a focus tube, in which the anti-cathode was a magnetic pole, some interesting observations were made with regard to the distribution of the fluorescence on the walls of the tube as the magnetic field varied. In order to explain the changes observed, the path of an electron in a radial field was investigated mathematically, and was found to lie on a right circular cone whose vertex coincides with the magnetic pole. If the surface of the cone is developed into a plane the trace of the path is a conic section, with the vertex as focus. This result continues to hold when an electric field, with its lines of force radiating from the same point, is superposed on the magnetic field. Although the actual distribution of electric intensity in a highly exhausted tube must differ widely from that here considered, the investigation sufficiently explains the facts observed. Theoretical . 2. The object is to find the path of a particle of mass m carrying a charge e in combined magnetic and electric fields, when the lines of force are radial and are such as might be due to a single pole of strength μ coincident with an electric charge k .

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