Experimental evidence for unstable waves in the lower E/Upper D-region excited near the bisector between the electric field and the drift velocity

1996 ◽  
Vol 23 (16) ◽  
pp. 2137-2140 ◽  
Author(s):  
T. A. Blix ◽  
E. V. Thrane ◽  
S. Kirkwood ◽  
Y. S. Dimant ◽  
R. N. Sudan
Keyword(s):  
Electric Field ◽  
Experimental Evidence ◽  
Drift Velocity ◽  
D Region

Electron drift velocity versus electric field in GaAs

1986 ◽  
Vol 29 (12) ◽  
pp. 1295-1296 ◽  
Author(s):  
Chian S. Chang ◽  
Harold R. Fetterman
Keyword(s):  
Electric Field ◽  
Drift Velocity ◽  
Electron Drift Velocity ◽  
Velocity Versus ◽  
Electron Drift

scholarly journals Mechanisms of the electron density depletion in the SAR arc region

1996 ◽  
Vol 14 (2) ◽  
pp. 211-221 ◽  
Author(s):  
A. V. Pavlov
Keyword(s):  
Electric Field ◽  
Magnetic Storm ◽  
Electron Density ◽  
Drift Velocity ◽  
Recovery Phase ◽  
Electron Densities ◽  
Model Framework ◽  
Vibrationally Excited ◽  
Plasma Drift ◽  
Excited Nitrogen

Abstract. This study compares the measurements of electron density and temperature and the integral airglow intensity at 630 nm in the SAR arc region and slightly south of this (obtained by the Isis 2 spacecraft during the 18 December 1971 magnetic storm), with the model results obtained using the time dependent one-dimensional mathematical model of the Earth\\'s ionosphere and plasmasphere. The explicit expression in the third Enskog approximation for the electron thermal conductivity coefficient in the multicomponent mixture of ionized gases and a simplified calculation method for this coefficient presents an opportunity to calculate more exactly the electron temperature and density and 630 nm emission within SAR arc region are used in the model. Collisions between N2 and hot thermal electrons in the SAR arc region produce vibrationally excited nitrogen molecules. It appears that the loss rate of O+(4S) due to reactions with the vibrationally excited nitrogen is enough to explain electron density depression by a factor of two at F-region heights and the topside ionosphere density variations within the SAR arc if the erosion of plasma within geomagnetic field tubes, during the main phase of the geomagnetic storm and subsequent filling of geomagnetic tubes during the recovery phase, are considered. To explain the disagreement by a factor 1.5 between the observed and modeled SAR arc electron densities an additional plasma drift velocity ~–30 m s–1 in the ion continuity equations is needed during the recovery phase. This additional plasma drift velocity is likely caused by the transition from convecting to corotating flux tubes on the equatorward wall of the trough. The electron densities and temperatures and 630 nm integral intensity at the SAR arc and slightly south of this region as measured for the 18 December 1971 magnetic storm were correctly described by the model without perpendicular electric fields. Within this model framework the effect of the perpendicular electric field ~100 mv m–1 with a duration ~1 h on the SAR arc electron density profiles was found to be large. However, this effect is small if ~1–2 h have passed after the electric field was set equal to zero.

scholarly journals Drift Velocity, Longitudinal and Transverse Diffusion in Hydrocarbons derived from Distributions of Single Electrons

1992 ◽  
Vol 45 (3) ◽  
pp. 351 ◽  
Author(s):  
Bernhard Schmidt ◽  
Michael Roncossek
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Drift Velocity ◽  
Simultaneous Measurement ◽  
Diffusion Coefficients ◽  
Number Density ◽  
Transverse Diffusion ◽  
Single Electrons ◽  
Time Of Flight Method

A time of flight method is described which allows the simultaneous measurement of drift velocity w and the ratios of the longitudinal and transverse diffusion coefficients to mobility (DL/JL, DT/JL) of electrons in gases. The accuracy achieved in this omnipurpose experiment is comparable with that of specialised techniques and is estimated to be �1 % for w and �5% for the D / JL measurements .. Results for methane, ethane, ethene, propane, propene and cyclopropane for values of E/N (the electric field strength divided by the number density) ranging from 0�02 to 15 Td are presented and discussed (1 Td = 10-21 Vm2 ).

Physical and chemical model of ion stability and movement within the dynamic and voltage-gated STM tip–surface tunneling junction

2017 ◽  
Vol 204 ◽  
pp. 159-172 ◽  
Author(s):  
Brandon E. Hirsch ◽  
Kevin P. McDonald ◽  
Steven L. Tait ◽  
Amar H. Flood
Keyword(s):  
Electric Field ◽  
Experimental Evidence ◽  
Electrostatic Interactions ◽  
Scanning Tunneling ◽  
Chemical Transformations ◽  
Tunneling Microscopy ◽  
Mobility Of Ions ◽  
Negative Surface ◽  
Ion Stability ◽  
And Migration

The interaction and mobility of ions in complex systems are fundamental to processes throughout chemistry, biology, and physics. However, nanoscale characterization of ion stability and migration remains poorly understood. Here, we examine ion movements to and from physisorbed molecular receptors at solution–graphite interfaces by developing a theoretical model alongside experimental scanning tunneling microscopy (STM) results. The model includes van der Waals forces and electrostatic interactions originating from the surface, tip, and physisorbed receptors, as well as a tip–surface electric field arising from the STM bias voltage (Vb). Our model reveals how both the electric field and tip–surface distance, dtip, can influence anion stability at the receptor binding sites on the surface or at the STM tip, as well as the size of the barrier for anion transitions between those locations. These predictions agree well with prior and new STM results from the interactions of anions with aryl-triazole receptors that order into functional monolayers on graphite. Scanning produces clear resolution at large magnitude negative surface biases (−0.8 V) while resolution degrades at small negative surface biases (−0.4 V). The loss in resolution arises from frequent tip retractions assigned to anion migration within the tip–surface tunneling region. This experimental evidence in combination with support from the model demonstrates a local voltage gating of anions with the STM tip inside physisorbed receptors. This generalized model and experimental evidence may help to provide a basis to understand the nanoscale details of related chemical transformations and their underlying thermodynamic and kinetic preferences.

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