scholarly journals Electrical and Polarimetric Radar Observations of a Multicell Storm in TELEX

2007 ◽  
Vol 135 (7) ◽  
pp. 2525-2544 ◽  
Author(s):  
Eric C. Bruning ◽  
W. David Rust ◽  
Terry J. Schuur ◽  
Donald R. MacGorman ◽  
Paul R. Krehbiel ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Negative Charge ◽  
Positive Charge ◽  
Three Dimensional ◽  
Phase Region ◽  
Polarimetric Radar ◽  
Radar Observations ◽  
Mapping Array ◽  
Lightning Initiation

Abstract On 28–29 June 2004 a multicellular thunderstorm west of Oklahoma City, Oklahoma, was probed as part of the Thunderstorm Electrification and Lightning Experiment field program. This study makes use of radar observations from the Norman, Oklahoma, polarimetric Weather Surveillance Radar-1988 Doppler, three-dimensional lightning mapping data from the Oklahoma Lightning Mapping Array (LMA), and balloon-borne vector electric field meter (EFM) measurements. The storm had a low flash rate (30 flashes in 40 min). Four charge regions were inferred from a combination of LMA and EFM data. Lower positive charge near 4 km and midlevel negative charge from 4.5 to 6 km MSL (from 0° to −6.5°C) were generated in and adjacent to a vigorous updraft pulse. Further midlevel negative charge from 4.5 to 6 km MSL and upper positive charge from 6 to 8 km (from −6.5° to −19°C) were generated later in quantity sufficient to initiate lightning as the updraft decayed. A negative screening layer was present near the storm top (8.5 km MSL, −25°C). Initial lightning flashes were between lower positive and midlevel negative charge and started occurring shortly after a cell began lofting hydrometeors into the mixed phase region, where graupel was formed. A leader from the storm’s first flash avoided a region where polarimetric radar suggested wet growth and the resultant absence of noninductive charging of those hydrometeors. Initiation locations of later flashes that propagated into the upper positive charge tracked the descending location of a polarimetric signature of graupel. As the storm decayed, electric fields greater than 160 kV m−1 exceeded the minimum threshold for lightning initiation suggested by the hypothesized runaway breakdown process at 5.5 km MSL, but lightning did not occur. The small spatial extent (≈100 m) of the large electric field may not have been sufficient to allow runaway breakdown to fully develop and initiate lightning.

scholarly journals Evolving Complex Electrical Structures of the STEPS 25 June 2000 Multicell Storm

2008 ◽  
Vol 136 (2) ◽  
pp. 741-756 ◽  
Author(s):  
Stephanie A. Weiss ◽  
W. David Rust ◽  
Donald R. MacGorman ◽  
Eric C. Bruning ◽  
Paul R. Krehbiel
Keyword(s):  
Great Plains ◽  
Negative Charge ◽  
Positive Charge ◽  
Three Dimensional ◽  
Lightning Flash ◽  
Severe Thunderstorm ◽  
Electrical Structure ◽  
High Reflectivity ◽  
Maximum Value ◽  
Mapping Array

Abstract Data from a three-dimensional lightning mapping array (LMA) and from two soundings by balloon-borne electric field meters (EFMs) were used to analyze the electrical structures of a multicell storm observed on 25 June 2000 during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). This storm had a complex, multicell structure with four sections, each of whose electrical structure differed from that of the others during all or part of the analyzed period. The number of vertically stacked charge regions in any given section of the storm ranged from two to six. The most complex charge and lightning structures occurred in regions with the highest reflectivity values and the deepest reflectivity cores. Intracloud flashes tended to concentrate in areas with large radar reflectivity values, though some propagated across more than one core of high reflectivity or into the low-reflectivity anvil. Intracloud lightning flash rates decreased as the vertical extent and maximum value of reflectivity cores decreased. Cloud-to-ground flash rates increased as cores of high reflectivity descended to low altitudes. Most cloud-to-ground flashes were positive. All observed positive ground flashes initiated between the lowest-altitude negative charge region and a positive charge region just above it. The storm’s complexity makes it hard to classify the vertical polarity of its overall charge structure, but most of the storm had a different vertical polarity than what is typically observed outside the Great Plains. The electrical structure can vary considerably from storm to storm, or even within the same storm, as in the present case.

scholarly journals BEM Modelling of High Voltage ELF electric field applied to a 3D pregnant woman model

2010 ◽  
Vol 6 (1) ◽  
pp. 31 ◽  
Author(s):  
Cristina Peratta ◽  
Andres Peratta ◽  
Dragan Poljak
Keyword(s):  
Pregnant Woman ◽  
Electric Field ◽  
Electric Fields ◽  
High Voltage ◽  
Medical Information ◽  
Three Dimensional ◽  
Low Frequency ◽  
Element Model ◽  
The Body ◽  
Geometrical Properties

The paper introduces a three dimensional multidomainboundary element model of a pregnant woman and foetus for the analysis of exposure to high voltage extremely low frequency electric fields. The definition of the differentphysical and geometrical properties of the relevant tissues is established according to medical information available in existing literature. The model takes into account changes in geometry, body mass, body fat, and overall chemical composition in the body which influence the electrical properties, throughout the different gestational periods. The developed model is used to solve the case of exposure to overhead power transmission lines at different stages of pregnancy including weeks 8, 13, 26 and 38. The results obtained are in line with those published in the earlier works considering different approaches. In addition, a sensitivity analysis involving varying scenarios of conductivity, foetus postures and geometry for each stage is defined and solved. Finally, a correlation between the externally applied electric field and the current density inside the foetus is established and the zones of maximum exposure are identified.

scholarly journals Analysis of Pole-Ascending–Descending Action by Insects Subjected to High Voltage Electric Fields

Insects ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 187 ◽  
Author(s):  
Yoshinori Matsuda ◽  
Yoshihiro Takikawa ◽  
Koji Kakutani ◽  
Teruo Nonomura ◽  
Hideyoshi Toyoda
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Negative Charge ◽  
Sitophilus Oryzae ◽  
Experimental System ◽  
Insect Behavior ◽  
Free Electrons ◽  
Current Voltage ◽  
Direct Current Voltage ◽  
Oppositely Charged

The present study was conducted to establish an electrostatic-based experimental system to enable new investigations of insect behavior. The instrument consists of an insulated conducting copper ring (ICR) linked to a direct current voltage generator to supply a negative charge to an ICR and a grounded aluminum pole (AP) passed vertically through the center of the horizontal ICR. An electric field was formed between the ICR and the AP. Rice weevil (Sitophilus oryzae) was selected as a model insect due to its habit of climbing erect poles. The electric field produced a force that could be imposed on the insect. In fact, the negative electricity (free electrons) was forced out of the insect to polarize its body positively. Eventually, the insect was attracted to the oppositely charged ICR. The force became weaker on the lower regions of the pole; the insects sensed the weaker force with their antennae, quickly stopped climbing, and retraced their steps. These behaviors led to a pole-ascending–descending action by the insect, which was highly reproducible and precisely corresponded to the changed expansion of the electric field. Other pole-climbing insects including the cigarette beetle (Lasioderma serricorne), which was shown to adopt the same behavior.

scholarly journals A Comprehensive Review of the Influence of Electric Field on Flame Characteristics

2020 ◽  
Author(s):  
Yin Ma ◽  
Tong Li ◽  
Jun Yan ◽  
Xiaorong Wang ◽  
Ji Gao ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Three Dimensional ◽  
Combustion Efficiency ◽  
Two Dimensions ◽  
Three Dimensional Model ◽  
High Pressure And Temperature ◽  
Soot Particles ◽  
Flame Dynamics ◽  
Important Means

Electric field assisted combustion is an important means to improve fuel combustion efficiency. This paper conducts extensive research on flame characteristics under different forms and different application methods of electric fields, emission of soot particles and simulation status. Different flame parameter measurement methods will lead to different degrees of error, and perfect numerical simulation can make simple predictions on experimental data. Most of the current numerical simulations are in two dimensions, and it is necessary to develop a complete and accurate three-dimensional model to simulate and predict the characteristics of the flame under an electric field. The emission of soot particles is also affected by the electric field, and reasonable electric field parameters can greatly reduce the emission of soot particles. It is recommended to conduct centralized measurement of different fuels under the electric field under high pressure and temperature conditions, so as to be able to develop a wider and more accurate flame dynamics and chemical model under the electric field.

scholarly journals Simulated Electrification of a Small Thunderstorm with Two-Moment Bulk Microphysics

2010 ◽  
Vol 67 (1) ◽  
pp. 171-194 ◽  
Author(s):  
Edward R. Mansell ◽  
Conrad L. Ziegler ◽  
Eric C. Bruning
Keyword(s):  
Charge Separation ◽  
Negative Charge ◽  
Positive Charge ◽  
Model Simulation ◽  
Particle Density ◽  
Phase Region ◽  
Number Concentration ◽  
Ice Crystals ◽  
Microphysics Scheme ◽  
Charge Structure

Abstract Electrification and lightning are simulated for a small continental multicell storm. The results are consistent with observations and thus provide additional understanding of the charging processes and evolution of this storm. The first six observed lightning flashes were all negative cloud-to-ground (CG) flashes, after which intracloud (IC) flashes also occurred between middle and upper levels of the storm. The model simulation reproduces the basic evolution of lightning from low and middle levels to upper levels. The observed lightning indicated an initial charge structure of at least an inverted dipole (negative charge above positive). The simulations show that noninductive charge separation higher in the storm can enhance the main negative charge sufficiently to produce negative CG flashes before upper-level IC flashes commence. The result is a “bottom-heavy” tripole charge structure with midlevel negative charge and a lower positive charge region that is more significant than the upper positive region, in contrast to the traditional tripole structure that has a less significant lower positive charge region. Additionally, the occurrence of cloud-to-ground lightning is not necessarily a result of excess net charge carried by the storm, but it is primarily caused by the local potential imbalance between the lowest charge regions. The two-moment microphysics scheme used for this study predicted mass mixing ratio and number concentration of cloud droplets, rain, ice crystals, snow, and graupel. Bulk particle density of graupel was also predicted, which allows a single category to represent a greater range of particle characteristics. (An additional hail category is available but was not needed for the present study.) The prediction of hydrometeor number concentration is particularly critical for charge separation at higher temperatures (−5° < T < −20°C) in the mixed phase region, where ice crystals are produced by rime fracturing (Hallett–Mossop process) and by splintering of freezing drops. Cloud droplet concentration prediction also affected the rates of inductive charge separation between graupel and droplets.

Relationships between Lightning Location and Polarimetric Radar Signatures in a Small Mesoscale Convective System

2009 ◽  
Vol 137 (12) ◽  
pp. 4151-4170 ◽  
Author(s):  
Nicole R. Lund ◽  
Donald R. MacGorman ◽  
Terry J. Schuur ◽  
Michael I. Biggerstaff ◽  
W. David Rust
Keyword(s):  
Mesoscale Convective System ◽  
Convective System ◽  
Polarimetric Radar ◽  
Mature Phase ◽  
Mesoscale Convective ◽  
Mapping Array ◽  
Lightning Initiation ◽  
Convective Cells ◽  
Differential Reflectivity ◽  
Kinematic Properties

Abstract On 19 June 2004, the Thunderstorm Electrification and Lightning Experiment observed electrical, microphysical, and kinematic properties of a small mesoscale convective system (MCS). The primary observing systems were the Oklahoma Lightning Mapping Array, the KOUN S-band polarimetric radar, two mobile C-band Doppler radars, and balloonborne electric field meters. During its mature phase, this MCS had a normal tripolar charge structure (lightning involved a midlevel negative charge between an upper and a lower positive charge), and flash rates fluctuated between 80 and 100 flashes per minute. Most lightning was initiated within one of two altitude ranges (3–6 or 7–10 km MSL) and within the 35-dBZ contours of convective cells embedded within the convective line. The properties of two such cells were investigated in detail, with the first lasting approximately 40 min and producing only 12 flashes and the second lasting over an hour and producing 105 flashes. In both, lightning was initiated in or near regions containing graupel. The upper lightning initiation region (7–10 km MSL) was near 35–47.5-dBZ contours, with graupel inferred below and ice crystals inferred above. The lower lightning initiation region (3–6 km MSL) was in the upper part of melting or freezing layers, often near differential reflectivity columns extending above the 0°C isotherm, which is suggestive of graupel formation. Both lightning initiation regions are consistent with what is expected from the noninductive graupel–ice thunderstorm electrification mechanism, though inductive processes may also have contributed to initiations in the lower region.

scholarly journals A Bond Bundle Case Study of Diels-Alder Catalysis Using Oriented Electric Fields

2022 ◽  
Author(s):  
Timothy Wilson ◽  
Mark Eberhart
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Electric Fields ◽  
Chemical Reactions ◽  
Catalytic Effect ◽  
Reaction Pathway ◽  
Three Dimensional ◽  
Atomic Charge ◽  
Diels Alder

Bond bundles are chemical bonding regions, analogous to Bader atoms, uniquely defined according to the topology of the gradient bundle condensed charge density, itself obtained by a process of infinitesimal partitioning of the three-dimensional charge density into differential zero-flux surface bounded regions. Here we use bond bundle analysis to investigate the response of the charge density to an oriented electric field in general, and the catalytic effect of such a field on Diels-Alder reactions in particular, which in this case is found to catalyze by allowing the transition state valance bond bundle configuration to be achieved earlier along the reaction pathway. Using precise numerical values, we arrive at the conclusion that chemical reactions and electric field catalysis can be understood in terms of intra-atomic charge density redistribution, i.e., that charge shifts within more so than between atoms account for the making and breaking of bonds.

scholarly journals A Bond Bundle Case Study of Diels-Alder Catalysis Using Oriented Electric Fields

2021 ◽  
Author(s):  
Timothy Wilson ◽  
Mark Eberhart
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Electric Fields ◽  
Chemical Reactions ◽  
Catalytic Effect ◽  
Reaction Pathway ◽  
Three Dimensional ◽  
Atomic Charge ◽  
Diels Alder

Bond bundles are chemical bonding regions, analogous to Bader atoms, uniquely defined according to the topology of the gradient bundle condensed charge density, itself obtained by a process of infinitesimal partitioning of the three-dimensional charge density into differential zero-flux surface bounded regions. Here we use bond bundle analysis to investigate the response of the charge density to an oriented electric field in general, and the catalytic effect of such a field on Diels-Alder reactions in particular, which in this case is found to catalyze by allowing the transition state valance bond bundle configuration to be achieved earlier along the reaction pathway. Using precise numerical values, we arrive at the conclusion that chemical reactions and electric field catalysis can be understood in terms of intra-atomic charge density redistribution, i.e., that charge shifts within more so than between atoms account for the making and breaking of bonds.

Three-dimensional analysis of the steady-state shape and small-amplitude oscillation of a bubble in uniform and non-uniform electric fields

1999 ◽  
Vol 384 ◽  
pp. 59-91 ◽  
Author(s):  
S. M. LEE ◽  
I. S. KANG
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Indirect Effect ◽  
Oscillation Frequency ◽  
Small Amplitude ◽  
Free Oscillation ◽  
Three Dimensional ◽  
Spherical Shape ◽  
Uniform Electric Field ◽  
Small Amplitude Oscillation

A three-dimensional analysis is performed to investigate the effects of an electric field on the steady deformation and small-amplitude oscillation of a bubble in dielectric liquid. To deal with a general class of electric fields, an electric field near the bubble is approximately represented by the sum of a uniform field and a linear field. Analytical results have been obtained for steady deformation and modification of oscillation frequency by using the domain perturbation method with the angular momentum operator approach.It has been found that, to the first order, the steady shape of a bubble in an arbitrary electric field can be represented by a linear combination of a finite number of spherical harmonics Yml, where 0[les ]l[les ]4 and [mid ]m[mid ][les ]l. For the oscillation about the deformed steady shape, the overall frequency modification from the value of free oscillation about a spherical shape is obtained by considering two contributions separately: (i) that due to the deformed steady shape (indirect effect), and (ii) that due to the direct effect of an electric field. Both the direct and indirect effects of an electric field split the (2l+1)-fold degenerate frequency of Yml modes, in the case of free oscillation about a spherical shape, into different frequencies that depend on m. However, when the average is taken over the (2l+1) values of m, the frequency splitting due to the indirect effect via the deformed steady shape preserves the average value, while the splitting due to the direct effect of an electric field does not.The oscillation characteristics of a bubble in a uniform electric field under the negligible compressibility assumption are compared with those of a conducting drop in a uniform electric field. For axisymmetric oscillation modes, deforming the steady shape into a prolate spheroid has the same effect of decreasing the oscillation frequency in both the drop and the bubble. However, the electric field has different effects on the oscillation about a spherical shape. The oscillation frequency increases with the increase of electric field in the case of a bubble, while it decreases in the case of a drop. This fundamental difference comes from the fact that the electric field outside the bubble exerts a suppressive surface force while the electric field outside the conducting drop exerts a pulling force on the surface.

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