| 1. |
- Cooray, Gerald, et al.
(author)
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Could Some Ball Lightning Observations be Optical Hallucinations Caused by Epileptic Seizures?
- 2008
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In: The Open Atmospheric Science Journal. - 1874-2823. ; 2, s. 101-105
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Journal article (peer-reviewed)abstract
- The great difficulty of encompassing all observed features of ball lightning into a single theory makes it highly probable that many observations and experiences which have no connection to ball lightning are also categorized as ball lightning experiences. In this note we compare the eyewitness reports of ball lightning and the symptoms of epileptic seizures of the occipital lobe as described in the medical literature and show that a person experiencing such a seizure for the first time may believe that he has witnessed a ball lightning event. Since many of the ball lightning reports are associated with nearby lightning strikes, the possibility that the rapidly changing magnetic field of a close lightning strike could trigger an epileptic seizure is analyzed. The results show that the time derivative of the magnetic field in the vicinity of an intense lightning flash is strong enough to stimulate neurons in the brain. This strengthens the possibility of inducing seizures in the occipital lobe of a person located in the vicinity of lightning strikes.
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| 2. |
- Cooray, Vernon, et al.
(author)
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Lightning caused injuries in humans
- 2009
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In: Lightning Protection. - London : The Institution of Engineering and Technology, London, UK. - 9780863417443
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Book chapter (pop. science, debate, etc.)
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| 3. |
- Cooray, Vernon, et al.
(author)
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Lightning caused injuries in humans
- 2007
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In: Journal of Electrostatics. - : Elsevier BV. - 0304-3886 .- 1873-5738. ; 65:5-6, s. 386-394
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Journal article (peer-reviewed)abstract
- A lightning flash may interact with humans in several ways. The possible pathways of interactions are direct strike, side flash, touch voltage, step voltage, subsequent stroke, connecting leaders and shock waves. The permanent or the temporary injuries that a victim suffers depend, among other parameters, on the type of interaction through which the body is exposed to a lightning strike and the path and the strength of the electric current passing through the body. In addition to the effects of electric current passing through the body, strong light and shock waves may also interact with the body in various ways. In this paper, the different types of injuries that may result from a lightning strike are documented and they are summarized, from engineering rather than a medical perspective
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| 4. |
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| 5. |
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| 6. |
- Amarasinghe, Dulan, et al.
(author)
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Channel tortuosity of long laboratory sparks
- 2007
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In: Journal of Electrostatics. - : Elsevier BV. - 0304-3886 .- 1873-5738. ; 65:8, s. 521-526
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Journal article (peer-reviewed)abstract
- Channel tortuosity of 50 cm long laboratory sparks were measured by analyzing a set of images taken by three cameras. The cameras were placed at a radial distance of 200 cm from the spark gap. The angle between any two cameras was 120 degrees. The sparks were generated between a steel rod and. a plane electrode. The distribution of the direction change of the channel was found to be Gaussian with a standard deviation of 15.3 degrees. The average tortuosity of the channel defined as the mean absolute value of the direction change was 11.8 +/- 1.4 degrees, which is smaller than the average tortuosity of natural lightning and close to the tortuosity of triggered lightning. The average tortuosity is dependent on the segment length used in calculating the direction change. A gradual increase in the average tortuosity (0.08 degrees/cm) was seen when the sparks propagated towards the plane electrode.
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| 7. |
- Amarasinghe, Dulan, et al.
(author)
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Correlation between brightness and channel currents of electrical discharges
- 2007
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In: IEEE transactions on dielectrics and electrical insulation. - 1070-9878 .- 1558-4135. ; 14:5, s. 1154-1160
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Journal article (peer-reviewed)abstract
- Channel brightness of 500 mm long electrical discharges were measured by analyzing a set of digitized images taken by 3 cameras placed symmetrically around a discharge gap at a radial distance of 200 cm from the axis of the spark. The sparks were generated between a steel rod and a plane electrode. The distribution of the brightness across the channel represented a Gaussian distribution. A linear correlation was seen between the channel brightness measured by different cameras looking at the same spark channel. No correlation was seen between the channel brightness and the channel depth (direction perpendicular to the camera plane). The measured peak current and the brightness of the main spark channel show a high degree of correlation (R-2=0.97). The sum of brightness of branches was equal to the brightness of the parent channel. One can use this result to calculate the relative distribution of branch currents in complex electrical discharges including natural lightning flashes. If the current in the parent channel is known, branch currents can be calculated by measuring the optical intensities using photographic techniques.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Arevalo, Liliana, et al.
(author)
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Numerical simulation of long laboratory sparks generated by positive switching impulses
- 2009
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In: Journal of Electrostatics. - : Elsevier BV. - 0304-3886 .- 1873-5738. ; 67:2-3, s. 228-234
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Journal article (peer-reviewed)abstract
- A numerical methodology using two different leader channel criteria has been implemented. The methodology is based on Bondiou and Gallimberti's proposition [A. Bondiou, I. Gallimberti, Theoretical modelling of the development of the positive spark in long spark, J. Phys. D: Appl. Phys. 27 (1994) 1252-1266]. The leader channel criteria used are Rizk engineering criterion [Rizk, A model for switching impulse leader inception and breakdown of long air gaps, IEEE Trans. Power Deliv., 4(1) (1989)] and Local thermodynamic - L.T.E. - physical concept [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193]. The methodology was tested in three different cases; a deterministic case, a statistical variation and a typical constant level test. Deterministic calculation considered corona inception using stabilization corona electric field criterion of Gallimberti [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193] and the leader moving as segments. The statistical simulation has two different statistical delays, one at inception and the other due to the tortuous characteristics of the leader channel. The constant level test consists of 200 positive switching impulses with the same characteristics such as maximum applied voltage, time to crest and time to fall. Time to breakdown and breakdown voltage were found based on the results obtained from the constant level test characteristics. All the numerical results presented are based on experimental conditions reported in [Les Renardières Group, Research on long gap discharges at Les Renardières, Electra N 35 (1973)] from the world class research group namely Les Renardieres Group.
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| 13. |
- Becerra Garcia, Marley, et al.
(author)
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Laboratory experiments cannot be utilized to justify the action of early streamer emission terminals
- 2008
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In: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 41:8
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Journal article (peer-reviewed)abstract
- The early emission of streamers in laboratory long air gaps under switching impulses has beenobserved to reduce the time of initiation of leader positive discharges. This fact has beenarbitrarily extrapolated by the manufacturers of early streamer emission devices to the case ofupward connecting leaders initiated under natural lightning conditions, in support of thosenon-conventional terminals that claim to perform better than Franklin lightning rods. In orderto discuss the physical basis and validity of these claims, a self-consistent model based on thephysics of leader discharges is used to simulate the performance of lightning rods in thelaboratory and under natural lightning conditions. It is theoretically shown that the initiation ofearly streamers can indeed lead to the early initiation of self-propagating positive leaders inlaboratory long air gaps under switching voltages. However, this is not the case for positiveconnecting leaders initiated from the same lightning rod under the influence of the electricfield produced by a downward moving stepped leader. The time evolution of the developmentof positive leaders under natural conditions is different from the case in the laboratory, wherethe leader inception condition is closely dependent upon the initiation of the first streamerburst. Our study shows that the claimed similarity between the performance of lightning rodsunder switching electric fields applied in the laboratory and under the electric field producedby a descending stepped leader is not justified. Thus, the use of existing laboratory results tovalidate the performance of the early streamer lightning rods under natural conditions is not justified.
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| 14. |
- Becerra Garcia, Marley, et al.
(author)
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Lightning striking distance of complex structures
- 2008
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In: IET Generation, Transmission & Distribution. - : Institution of Engineering and Technology (IET). - 1751-8687 .- 1751-8695. ; 2:1, s. 131-138
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Journal article (peer-reviewed)abstract
- Traditionally, the location of lightning strike points has been determined byusing the rolling sphere method, but recently the collection volumemethod (CVM) has also been proposed for the placement ofair terminals on complex structures. Both these methods are empiricalin nature and a more advanced model based on physicsof discharges is needed to improve the state of affairs.This model is used to evaluate the striking distance fromcorners and air terminals on actual buildings and the resultsare qualitatively compared with the predictions of the rolling spheremethod and the CVM. The results show that the strikingdistance not only depends upon the prospective return stroke currentand the geometry of the building, but also on thelateral position of the downward leader with respect to thestrike point. A further analysis is performed to qualitatively comparethe lightning attraction zones obtained with the CVM and theleader inception zones obtained for a building with and withoutair terminals. The obtained results suggest that the collection volumeconcept overestimates the protection areas of air terminals placed oncomplex structures, bringing serious doubts on the validity of this method.
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| 15. |
- Becerra Garcia, Marley, et al.
(author)
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On the velocity of lightning upward connecting positive leaders
- 2007
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In: IX International Symposium onLightning Protection.
-
Conference paper (peer-reviewed)abstract
- The point of interception of the downward movinglightning leader by a newly created upward connectingleader depends upon the velocity of both leaders. Eventhough measurements and estimates of the velocity ofdownward moving lightning leaders are more common in theliterature, only few values of the velocity of upwardconnecting leaders have been reported. In this paper, a selfconsistentleader propagation model is used to estimate thevelocity of upward connecting positive leaders initiated froma tall tower under the influence of downward negativelightning leaders. It is predicted that an upward connectingleader propagates with low velocity (lower than about 5 x103 m s-1) immediately after the creation of the first leadersegment. It is not until the electric field produced by thedownward leader is high enough for the continuousacceleration of the leader channel, when the upward leadervelocity reaches values close to the ones observed inlaboratory (about 1-2 x 104 m s-1). Then, the connectingleader continues its movement with increasing velocity untilit intercepts the downward moving leader. The propagationof upward connecting leaders has been found to beinfluenced by the prospective return stroke current, theaverage velocity and the lateral position of the downwardleader channel as well as by the ambient field. This resultclearly shows that the velocity and propagation time ofupward connecting positive leaders change from flash toflash and they cannot be generalized by assuming a givenvelocity ratio of both leaders as it is assumed by the existingleader progression models.
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| 16. |
- Becerra Garcia, Marley, et al.
(author)
-
On the velocity of positive connecting leaders associated with negative downward lightning leaders
- 2008
-
In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 35:2
-
Journal article (peer-reviewed)abstract
- A self-consistent leader propagation model is used to estimate the velocity of upward connecting positive leaders initiated from a tall tower under the influence of downward negative lightning leaders. The propagation of upward connecting leaders has been found to be influenced not only by the average velocity of the downward leader but also by the prospective return stroke current, the lateral position of the downward leader channel as well as by the ambient electric field. This result show that the velocity and propagation time of upward connecting positive leaders change from flash to flash due to the variations in these parameters.
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| 17. |
- Becerra Garcia, Marley, et al.
(author)
-
The early streamer emission principle does not work under natural lightning!
- 2007
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In: IX International Symposium on Lightning Protection.
-
Conference paper (peer-reviewed)abstract
- An appropriate evaluation of the efficiency of airterminals is a key factor for the discussion of the claimedadvantages of the Early Streamer Emission devices ESEcompared to the conventional Franklin rods. In order todiscuss the physical basis and validity of the ESE claim, aself-consistent physical model is used to simulate theperformance of an air terminal under laboratory and undernatural lightning conditions. It is theoretically shown thatthe early initiation of streamers can indeed lead to the soonerinitiation of a self-propagating positive leader in a laboratorylong air gap under switching voltages. However, this is notthe case for positive leaders initiated from the same terminalunder the influence of the electric field produced by thedescent of a downward moving lightning leaders. The timeevolution of the leader development under natural conditionsis different to the case in laboratory, where the leaderinception condition is closely dependant upon the streamerinititation. This is mainly because of the differences in thetime variation of the electric field applied in laboratory andthat produced by the approach of the downward leader.Therefore, it is found that the claimed similarity between theswitching electric fields applied in laboratory and the electricfield produced by the descent of a negative downward leader,used in the literature to extrapolate the early streameremission principle to natural lightning, is not true.
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| 18. |
- Becerra, Marley, et al.
(author)
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A self-consistent upward leader propagation model
- 2006
-
In: Journal of Physics D. - : Institute of Physics Publishing (IOPP). - 0022-3727 .- 1361-6463. ; 39:16, s. 3708-3715
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Journal article (peer-reviewed)abstract
- The knowledge of the initiation and propagation of an upward movingconnecting leader in the presence of a downward moving lightning steppedleader is a must in the determination of the lateral attraction distance of alightning flash by any grounded structure. Even though different models that simulate this phenomenon are available in the literature, they do not take into account the latest developments in the physics of leader discharges. Theleader model proposed here simulates the advancement of positive upward leaders by appealing to the presently understood physics of that process.The model properly simulates the upward continuous progression of thepositive connecting leaders from its inception to the final connection withthe downward stepped leader (final jump). Thus, the main physical properties of upward leaders, namely the charge per unit length, the injected current, the channel gradient and the leader velocity are self-consistentlyobtained. The obtained results are compared with an altitude triggeredlightning experiment and there is good agreement between the modelpredictions and the measured leader current and the experimentally inferredspatial and temporal location of the final jump. It is also found that the usualassumption of constant charge per unit length, based on laboratoryexperiments, is not valid for lightning upward connecting leaders.
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| 19. |
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| 20. |
- Becerra, Marley, et al.
(author)
-
A simplified physical model to determine the lightning upward connecting leader inception
- 2006
-
In: IEEE Transactions on Power Delivery. - 0885-8977 .- 1937-4208. ; 21:2, s. 897-908
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Journal article (peer-reviewed)abstract
- In this paper, a generalized leader inception model isproposed. It is based on an iterative geometrical analysis of thebackground potential distribution of an earthed structure to simulatethe first meters of propagation of an upward connecting leader.By assuming a static field approach, the leader stabilization fieldsand the striking distances were computed for a lightning rod andfor a building. The obtained results were compared with the existingleader inception criteria. Furthermore, in order to validatethe model, the leader inception condition was computed for a triggeredlightning experiment. Excellent agreement with the experimentalresults was obtained. The present model has several advantagesin comparison with the existing leader inception criteria.One of them is related to the fact that the proposed model can beused to analyze the effect of the space charge on the upward leaderinception.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Becerra, Marley, et al.
(author)
-
Effect of the space charge layer created by corona at ground level on the inception of upward lightning leaders from tall towers
- 2007
-
In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112:D12, s. D12205-
-
Journal article (peer-reviewed)abstract
- Electric field measurements above ground have shown that the space charge layer created by corona at ground level shields the background electric field produced by the thundercloud. Therefore it is expected that this space charge layer can also influence the conditions required to initiate upward lightning from tall objects. For this reason, a numerical model that describes the evolution of the main electrical parameters below a thunderstorm is used to compute the space charge layer development. The time variation of the electric field measured at 600 m above ground during the 1989 rocket triggered lightning experiment at the Kennedy Space Center (Florida) is used to drive the model. The obtained space charge density profiles are used to compute the conditions required to initiate stable upward lightning positive leaders from tall towers. Corona at the tip of the tower is neglected. It is found that the space charge layer significantly affects the critical thundercloud electric fields required to initiate upward lightning leaders from tall objects. The neutral aerosol particle concentration is observed to have a significant influence on the space charge density profiles and the critical thundercloud electric fields, whereas the corona current density does not considerably affect the results for the cases considered in the analysis. It is found that a lower thundercloud electric field is required to trigger a lightning flash from a tall tower or other tall slender grounded structure in the case of sites with a high neutral aerosol particle concentration, like polluted areas or coastal regions.
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| 26. |
- Becerra, Marley, et al.
(author)
-
Identification of lightning vulnerability points on complex grounded structures
- 2007
-
In: Journal of Electrostatics. - : Elsevier BV. - 0304-3886 .- 1873-5738. ; 65:9, s. 562-570
-
Journal article (peer-reviewed)abstract
- The identification of the most vulnerable points on a given structure to be struck by lightning is an important issue on the design of a reliable lightning protection system. Traditionally, these lightning strike points are identified using the rolling sphere method, through an empirical correlation with the prospective peak return stroke current. However, field observations in Kuala Lumpur and Singapore have shown that the points where lightning flashes strike buildings also depend on the height and geometry of the structure. Since a lightning strike point is believed to be the place on a grounded structure where a propagating upward leader is first initiated, a physical leader inception model is used here to estimate the background electric field required to initiate a stable upward leader from the corners of some complex buildings. The computed location of the points from where leaders are incepted are compared with the damaged points on buildings struck by lightning. The observed lightning strike points coincide rather well with the corners of the buildings which are characterized by lower leader inception electric fields. Furthermore, it is found that the geometry of the buildings significantly influences the conditions necessary to initiate upward leaders and, therefore, the location of the most likely strike points.
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| 27. |
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| 28. |
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| 29. |
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| 30. |
- Becerra, Marley, 1979-
(author)
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On the Attachment of Lightning Flashes to Grounded Structures
- 2008
-
Doctoral thesis (other academic/artistic)abstract
- This thesis deals with the physical modeling of the initiation and propagation of upward positive leader discharges from grounded structures during lightning strikes. It includes the analysis of upward leaders initiated under the influence of the electric field produced by a dominant negative cloud charge and due to the combined action of a negative thundercloud and a descending downward stepped negative leader. Thus, a self-consistent model based on the physics of leader discharges is developed for the evaluation of the attachment of lightning flashes to any kind of grounded structure. The predictions of the model have been found to be in good agreement with the results of laboratory long air gap experiments and with classical and altitude rocket triggered lightning experiments. Due to the high application level and predictive power of the developed model, several contributions to the physical understanding of factors influencing the initiation and propagation of upward positive leaders during thunderstorms have been made. For instance, it has been found that the initiation of upward connecting leaders is strongly affected by the average velocity of the downward stepped leader. Similarly, it is shown that the switching voltage impulses used in the laboratory do not “fairly approximate” the electric fields produced by a descending downward leader, as claimed by supporters of Early Streamer Emission (ESE) devices. Furthermore, it is found that the space charge layer created by corona at ground level significantly increases the thundercloud electric fields required to initiate upward lightning leaders from tall objects. On the other hand, it is also shown that the upward leader velocity depends on the downward leader average velocity, the prospective return stroke current, the lateral distance of the downward leader channel and the ambient electric field. By implementing the model to the analysis of complex structures, it has been observed that the corners of actual buildings struck by lightning coincide rather well with the places characterized by low leader inception electric fields. Besides, it has been found that the leader inception zones of the corners of complex structures do not define symmetrical and circular regions as it is generally assumed.
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| 31. |
- Becerra, Marley, et al.
(author)
-
On the interaction of lightning upward connecting positive leaders with humans
- 2009
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In: IEEE transactions on electromagnetic compatibility (Print). - USA : IEEE. - 0018-9375 .- 1558-187X. ; 51:4, s. 1001-1008
-
Journal article (peer-reviewed)abstract
- Upward connecting leaders can be initiated from humans under the influence of lightning downward stepped leaders, thereby causing severe injuries. In order to improve the scarce knowledge about the interaction of upward connecting leaders with humans, a self-consistent model based on the physics of leader discharges is used in this paper. Furthermore, a current-generation-type return-stroke model is applied to calculate the current pulse produced during the neutralization of unsuccessful aborted upward leaders. It is estimated that an upward connecting leader can be initiated even when the victim is located several tens of meters away from the lightning channel. However, the lightning exposure to a direct strike and to an aborted leader is found to be reduced by 50% and 70%, respectively, when an individual standing straight adopts the squat position. In the case of an aborted upward leader, it is estimated that a short-duration pulse of opposite polarity in the kiloampere range would be produced by the neutralization of the leader charge. Rough estimates of the total energy dissipated in the victim's body by the current of an aborted unsuccessful upward leader range between hundred and thousand joules.
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| 32. |
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| 33. |
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| 34. |
- Becerra, Marley, et al.
(author)
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Time dependent evaluation of the lightning upward connecting leader inception
- 2006
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In: Journal of Physics D. - : Institute of Physics Publishing (IOPP). - 0022-3727 .- 1361-6463. ; 39:21, s. 4695-4702
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Journal article (peer-reviewed)abstract
- The evaluation of the upward connecting leader inception from a grounded structure has generally been performed neglecting the effect of the propagation of the downward stepped leader. Nevertheless, field observations suggest that the space charge produced by streamer corona andaborted upward leaders during the approach of the downward lightning leader can influence significantly the initiation of stable upward positive leaders. Thus, a physical leader inception model is developed, which takes into account the electric field variations produced by the descending leader during the process of inception. Also, it accounts for the shielding effect produced by streamer corona and unstable leaders formed before the stable leader inception takes place. The model is validated by comparing its predictions with the results obtained in long gap experiments and in an altitude triggered lightning experiment. The model is then used to estimate the leader inception conditions for free standing rods as a function of tip radius and height. It is found that the rod radius slightly affects the height of the downward leader tip necessary to initiate upward leaders. Only an improvement of about 10% on the lightning attractiveness can be reached byusing lightning rods with an optimum radius. Based on the obtained results, the field observations of competing lightning rods are explained. Furthermore, the influence of the average stepped leader velocity on theinception of positive upward leaders is evaluated. The results obtained show that the rate of change of the background electric field produced by a downward leader descent largely influences the conditions necessary for upward leader initiation. Estimations of the leader inception conditions for the upper and lower limit of the measured values of the average downward lightning leader velocity differ by more than 80%. In addition, the striking distances calculated taking into account the temporal change of the background field are significantly larger than the ones obtained assuming a static downward leader field. The estimations of the present model are alsocompared with the existing leader inception models and discussed.
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| 35. |
- Becerra, Marley, et al.
(author)
-
Velocity of Laboratory Electrical Discharges at low Pressure
- 2006
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Conference paper (peer-reviewed)abstract
- One of the most important characteristics of sprite development is the velocity of the downward tendrils, which has been observed to range from 105 to 3x107 m/s (Moudry et al., JGR, 29, 2002). However, there is a lack of laboratory experimental data on the speed of propagation of electrical discharges at pressures similar to those encountered in the sprite environment. In order to gather more information on this topic, the average velocity of propagation of electrical discharges in quasi-uniform electric fields in air at pressures ranging from 1 to 10 mBar has been measured from optical emission. In the laboratory, the discharge is confined in a glass tube of 0.09 m diameter and between the electrodes placed 0.8 m apart. Each electrode has an equivalent radius of 0.25 m and is segmented into two concentric sections, one of them placed inside the tube. The voltage impulses applied to the cathode and the anode have a risetime of about 20 ns and a decay (half-value) time of 2 ms. The light from the discharge is detected with two optical fibers connected to photomultipliers Hamamatsu R1477-06, placed at 0.05 m from the electrodes. For each considered pressure, a set of impulse voltages with increasing peak values are applied. The lowest voltage applied at a particular pressure corresponds to the voltage for which light signals are detected. The average development velocities of the discharges at 1, 4 and 10 mBar are estimated from the measured optical signatures. For the considered pressures, the measured discharge velocity ranged from 1.5x105 to 1.5x107 m/s for reduced electric fields E/N (where E is the average electric field and N is the gas density) ranging from 120 to 1200 Td. This range of measured discharge velocities correspond to observed velocities of downward tendrils in sprites. In addition, a well-defined empirical relationship as given below, is found between the reduced discharge velocity v/N and the reduced electric field E/N in the range of pressures considered: v/N=102.002log(E/N)-5.234 [10-6 m4/s]
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| 36. |
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| 37. |
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| 38. |
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| 39. |
- Cooray, Vernon, et al.
(author)
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A current generation type return stroke model that predicts the return stroke velocity
- 2007
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In: Journal of Lightning Research. - 1652-8034. ; 1, s. 32-39
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Journal article (peer-reviewed)abstract
- AbstractThe engineering return stroke models available in the literature can be divided into current generation andcurrent propagation types, which are also referred to as the traveling current source type and transmission linetype, respectively. In the current propagation models the return stroke channel serves as a guiding structure forthe return stroke current which is injected at ground level. In the current generation models each channelsection acts as a current source which is turned on by the arrival of the return stroke front at that channelsection. Once turned on, the current source associated with the channel section injects a current, called a coronacurrent, into the core of the return stroke channel. This current contribution is assumed to travel to groundalong the core of the return stroke channel with the speed of light in vacuum. In the current generation typereturn stroke models available today, the channel base current and the return stroke velocity together with eitherthe distribution of the charge neutralized during the return stroke or the temporal variation of the coronacurrent are assumed as input parameters. With these input parameters, model outputs are the spatial andtemporal variation of the return stroke current and either the temporal variation of the corona current or thedistribution of the charge neutralized by the return stroke, depending on the input parameters selected in themodel. In this paper, we utilize a current generation type return stroke model to predict the return stroke velocityusing the channel base current, distribution of the charge neutralized by the return stroke, and the temporalvariation of the corona current as input parameters. We will show that for physically reasonable inputparameters the predicted return stroke velocity initially increases with height, reaches a peak, and then decreaseswith increasing height.
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| 40. |
- Cooray, Vernon
(author)
-
A novel procedure to represent lightning return strokes : current dissipation return stroke models
- 2009
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In: IEEE transactions on electromagnetic compatibility (Print). - USA : IEEE. - 0018-9375 .- 1558-187X. ; 51:3, s. 748-755
-
Journal article (peer-reviewed)abstract
- Engineering return stroke models available in the literature can be divided into two categories, namely, current propagation models and current generation models. Based on the theory of pulse propagation along transmission lines in the presence of corona, a third procedure to describe return strokes, which, in fact, is the inverse of current generation models, is introduced. Models based on the new concept are called current dissipation models. In the current generation models, the corona currents generated by the neutralization of the corona sheath travel downward and the cumulative effects of these corona currents generate the return stroke current. In current dissipation models, the return stroke is initiated by a current pulse injected into the core of the leader channel at ground level. This injected current pulse travels upward with speed vc . If the return stroke channel is treated as a transmission line, then this speed is equal to the speed of light. The propagation of this pulse along the central core initiates the neutralization of the corona sheath leading to the release of corona currents into the central core. In contrast to current generation models in which corona currents travel downward, these corona currents travel upward along the core. The speed of propagation of the corona pulses upward along the core is also equal to vc. The corona currents, being of opposite polarity, lead to the dissipation of the injected current pulse. As in the case of current generation models, a current dissipation model can be described completely by any three of the following four parameters. They are: 1) channel base current; 2) spatial variation of the return stroke velocity; 3) spatial variation of the corona decay time constant; and 4) the spatial variation of the positive charge deposited by the return stroke on the leader channel. It is also shown that current propagation models available in the literature are special cases of current dissipation models.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
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| 45. |
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| 46. |
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| 47. |
- Cooray, Vernon, et al.
(author)
-
Guest editorial
- 2007
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In: Journal of Electrostatics. - : Elsevier BV. - 0304-3886. ; 65:5-6, s. 281-
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Journal article (peer-reviewed)abstract
- From the 13th to 16th of September, 2004 researchers active in the fields of physics of lightning and lightning protection gathered in Avignon, France for the 27th International Conference on Lightning Protection (ICLP). Traditionally, the ICLP provides authoritative reviews of the progress and state of research, as well as opportunity for personal contact between the entire community of lightning researchers. The printed proceedings of previous ICLP conferences enjoyed considerable prestige on a worldwide basis. At the Avignon conference, over 150 papers presenting the entire range of lightning research and protection were presented by scientists from more than 30 countries throughout the world. We cannot claim to have collected a balanced overview of the entire conference, but we believe that the papers that survived the review process, first by the session chairmen and then by the strict anonymous review process of the Journal of Electrostatics, and that are included herein, represent some of the best current research in lightning and its effects. Naturally, any collection of papers in a single field creates a heavy burden of reviewing. We would like to thank session chairmen and many anonymous referees for their valuable, indispensable cooperation in the reviewing process of these papers. We also wish to thank Prof. Mark Horenstein, the Editor of the Journal of Electrostatics, for support of this issue.
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| 48. |
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| 49. |
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| 50. |
- Cooray, Vernon, et al.
(author)
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Lightning parameters of engineering interest
- 2009
-
In: Lightning Protection. - London : The Institution of Engineering and Technology, London, UK. - 9780863417443
-
Book chapter (pop. science, debate, etc.)
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