Parallel electric fields in mixing hot and cold plasmas in the auroral downward current region: Double layers and ambipolar fields

2009 ◽  
Vol 114 (A3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Nagendra Singh ◽  
Kalyan Arcot ◽  
B. E. Wells
Keyword(s):  
Electric Fields ◽  
Double Layers ◽  
Cold Plasmas ◽  
Current Region

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.

scholarly journals Electric fields and double layers in plasmas

1987 ◽  
Vol 5 (2) ◽  
pp. 233-255 ◽  
Author(s):  
Nagendra Singh ◽  
H. Thiemann ◽  
R. W. Schunk
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Electric Fields ◽  
Sheet Thickness ◽  
High Density ◽  
Effective Length ◽  
Double Layers ◽  
Low Density ◽  
Ambient Magnetic Field ◽  
Cold Plasmas

Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamic features of the double layers are discussed. These features, as seen in simulations, laboratory experiments and theory, indicate that double layers and the currents through them undergo slow oscillations, which are determined by the ion transit time across an effective length of the system in which the double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations have been considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields (parallel to an ambient magnetic field) and double layers in an expanding plasma are discussed.

scholarly journals Functionalized Silicon Electrodes Toward Electrostatic Catalysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Long Zhang ◽  
Xiaohua Yang ◽  
Shun Li ◽  
JianMing Zhang
Keyword(s):  
Electric Fields ◽  
Silicon Surfaces ◽  
Double Layers ◽  
External Electric Fields ◽  
Space Charges ◽  
Surface Models ◽  
Solid Liquid ◽  
Static Electric Fields ◽  
Mediator Catalysis

Oriented external electric fields are now emerging as “smart effectors” of chemical changes. The key challenges in experimentally studying electrostatic catalysis are (i) controlling the orientation of fields along the reaction axis and (ii) finely adjusting the magnitudes of electrostatic stimuli. Surface models provide a versatile platform for addressing the direction of electric fields with respect to reactants and balancing the trade-off between the solubility of charged species and the intensity of electric fields. In this mini-review, we present the recent advances that have been investigated of the electrostatic effect on the chemical reaction on the monolayer-functionalized silicon surfaces. We mainly focus on elucidating the mediator/catalysis role of static electric fields induced from either solid/liquid electric double layers at electrode/electrolyte interfaces or space charges in the semiconductors, indicating the electrostatic aspects is of great significance in the semiconductor electrochemistry, redox electroactivity, and chemical bonding. Herein, the functionalization of silicon surfaces allows scientists to explore electrostatic catalysis from nanoscale to mesoscale; most importantly, it provides glimpses of the wide-ranging potentials of oriented electric fields for switching on/off the macroscale synthetic organic electrochemistry and living radical polymerization.

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).

Particle Compaction with Alternating Electric Fields: The Effects of Electrode Geometry

1986 ◽  
Vol 73 ◽  
Author(s):  
Alan J. Hurd
Keyword(s):  
Electric Fields ◽  
Colloidal Particles ◽  
Dielectric Material ◽  
Double Layers ◽  
Electrode Geometry ◽  
Dipole Interactions ◽  
Alternating Electric Fields ◽  
Alternating Electric Field ◽  
Dc Bias ◽  
Induced Dipoles

ABSTRACTA technique for inducing ordered, close-packed arrangements of various symmetries among colloidal particles is discussed. An external alternating electric field applied to the colloid induces dipole interactions of variable strength by polarizing either the dielectric material of the particles or their electrostatic double layers. Ordering in various symmetries can be obtained by switching the field rapidly between pairs of electrodes, thereby changing the orientation of the induced dipoles. A small dc bias serves to deposit and compact the aligned particles.

Conditions for establishing quasistable double layers in the Earth’s auroral upward current region

2010 ◽  
Vol 17 (12) ◽  
pp. 122901 ◽  
Author(s):  
D. S. Main ◽  
D. L. Newman ◽  
R. E. Ergun
Keyword(s):  
Double Layers ◽  
Current Region ◽  
Upward Current

scholarly journals Volume ignition of laser driven fusion pellets and double layer effects

1988 ◽  
Vol 6 (2) ◽  
pp. 163-182 ◽  
Author(s):  
L. Cicchitelli ◽  
S. Eliezer ◽  
M. P. Goldsworthy ◽  
F. Green ◽  
H. Hora ◽  
...  
Keyword(s):  
Electric Fields ◽  
Inertial Confinement Fusion ◽  
Laser Pulses ◽  
Spark Ignition ◽  
State Density ◽  
Double Layers ◽  
Inertial Confinement ◽  
Confinement Fusion ◽  
Volume Compression ◽  
Volume Ignition

The realization of an ideal volume compression of laser-irradiated fusion pellets (by C. Yamanaka) opens the possibility for an alternative to spark ignition proposed for many years for inertial confinement fusion. A re-evaluation of the difficulties of the central spark ignition of laser driven pellets is given. The alternative volume compression theory, together with volume burn and volume ignition (discovered in 1977), have received less attention and are re-evaluated in view of the experimental verification by Yamanaka, generalized fusion gain formulas, and the variation of optimum temperatures derived at self-ignition. Reactor-level DT fusion with MJ-laser pulses and volume compression to 50 times the solid-state density are estimated. Dynamic electric fields and double layers at the surface and in the interior of plasmas result in new phenomena for the acceleration of thermal electrons to suprathermal electrons. Double layers also cause a surface tension which stabilizes against surface wave effects and Rayleigh–Taylor instabilities.

Dynamic Electric Fields and Double Layers in Laser-Produced Plasmas

1989 ◽  
Vol 16 (4) ◽  
pp. 419-463 ◽  
Author(s):  
Shalom Eliezer ◽  
Heinrich Hora
Keyword(s):  
Electric Fields ◽  
Double Layers

scholarly journals Dynamical behavior of U-shaped double layers: cavity formation and filamentary structures

2005 ◽  
Vol 12 (6) ◽  
pp. 783-798 ◽  
Author(s):  
N. Singh ◽  
C. Deverapalli ◽  
A. Rajagiri ◽  
I. Khazanov
Keyword(s):  
Electric Fields ◽  
Large Amplitude ◽  
Electron Beams ◽  
Ion Beam ◽  
Plasma Heating ◽  
Dynamical Behavior ◽  
Ion Beams ◽  
Double Layers ◽  
Lower Hybrid ◽  
Ps Ii

Abstract. Observations from the Polar and FAST satellites have revealed a host of intriguing features of the auroral accelerations processes in the upward current region (UCR). These features include: (i) large-amplitude parallel ( ) and perpendicular () fluctuating as well as quasi-static electric fields in density cavities, (ii) fairly large-amplitude unipolar parallel electric fields like in a strong double layer (DL), (iii) variety of wave modes, (iv) counter-streaming of upward going ion beams and downward accelerated electrons, (v) horizontally corrugated bottom region of the potential structures (PS), in which electron and ion accelerations occur, (vi) filamentary ion beams in the corrugated PS, and (vii) both upward and downward moving narrow regions of parallel electric fields, inferred from the frequency drifts of the auroral kilometric radiations. Numerical simulations of U-shaped potential structures reveal that such observed features of the UCR are integral parts of dynamically evolving auroral U-shaped potential structures. Using a 2.5-D particle-in-cell (PIC) code we simulate a U-shaped broad potentialstructure (USBPS). The dynamical behavior revealed by the simulation includes: (i) recurring redistribution of the parallel potential drop (PPD) in the PS, (ii) its up and downward motion, (iii) formation of filaments in the potential and density structures, and (iv) creation of filamentary as well as broad extended density cavities. The formation of the filamentary structures is initiated by an ion-beam driven instability of an oblique ion mode trapped inside a broad cavity, when it becomes sufficiently thin in height. The filaments of the PS create filamentary electron beams, which generate waves at frequencies above the lower hybrid frequency, affecting plasma heating. This results in plasma evacuation and formation of a cavity extended in height. The waves associated with filamentary electron beams also evolve into electron holes. The transverse and parallel scale lengths of the regions with large and as well as their magnitudes are compared with satellite data.

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