| 1. |
- Cooray, Vernon, 1952-, et al.
(författare)
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A Novel Interpretation of the Electromagnetic Fields of Lightning Return Strokes
- 2019
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Ingår i: Atmosphere. - : MDPI. - 2073-4433 .- 2073-4433. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Electric and/or magnetic fields are generated by stationary charges, uniformly moving charges and accelerating charges. These field components are described in the literature as static fields, velocity fields (or generalized Coulomb field) and radiation fields (or acceleration fields), respectively. In the literature, the electromagnetic fields generated by lightning return strokes are presented using the field components associated with short dipoles, and in this description the one-to-one association of the electromagnetic field terms with the physical process that gives rise to them is lost. In this paper, we have derived expressions for the electromagnetic fields using field equations associated with accelerating (and moving) charges and separated the resulting fields into static, velocity and radiation fields. The results illustrate how the radiation fields emanating from the lightning channel give rise to field terms varying as 1/r and 1/r2, the velocity fields generating field terms varying as 1/r2, and the static fields generating field components varying as 1/r2 and 1/r3. These field components depend explicitly on the speed of propagation of the current pulse. However, the total field does not depend explicitly on the speed of propagation of the current pulse. It is shown that these field components can be combined to generate the field components pertinent to the dipole technique. However, in this conversion process the connection of the field components to the physical processes taking place at the source that generate these fields (i.e., static charges, uniformly moving charges and accelerating charges) is lost.
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| 2. |
- Cooray, Vernon, 1952-, et al.
(författare)
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Comment on "Straight lightning as a signature of macroscopic dark matter"
- 2022
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 105:8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In the discussed paper [N. Starkman, H. Winch, J. S. Sidhu, and G. Starkman, Straight lightning as a signature of macroscopic dark matter, Phys. Rev. D 103, 063024 (2021)], the authors have made several assumptions and statements concerning the initiation and propagation of lightning flashes induced by macroscopic dark matter passing through the atmosphere. The authors suggest that the path of dark matter can be identified by looking for lightning with straight channels, although such channels have not been previously reported. Even though we agree with the suggestion of the authors that macroscopic dark matter could, in theory, give rise to straight lightning channels, there are several statements in the paper that are not sufficiently clear and which could lead to misinterpretation. Our comments on the paper are the following.
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| 3. |
- Cooray, Vernon, 1952-, et al.
(författare)
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Could Macroscopic Dark Matter (Macros) Give Rise to Mini-Lightning Flashes out of a Blue Sky without Clouds?
- 2021
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Ingår i: Atmosphere. - : MDPI. - 2073-4433 .- 2073-4433. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- A recent study pointed out that macroscopic dark matter (macros) traversing through the Earth's atmosphere can give rise to hot and ionized channels similar to those associated with lightning leaders. The authors of the study investigated the possibility that when such channels created by macros pass through a thundercloud, lightning leaders may be locked in by these ionized channels, creating lightning discharges with perfectly straight channels. They suggested the possibility of detecting such channels as a means of detecting the passage of macros through the atmosphere. In this paper, we show that such macros crossing the atmosphere under fair weather conditions could also give rise to mini-lightning flashes with current amplitudes in the order of a few hundred Amperes. These mini-lightning flashes would generate a thunder signature similar to or stronger than those of long laboratory sparks and they could also be detected by optical means. As in the case of thunderstorm-assisted macro lightning, these mini-lightning flashes are also associated with straight channels. Moreover, since the frequency of mini-lightning flashes is about thirty times greater than the macro-generated lightning flashes assisted by thunderstorms, they could be used as a means to look for the paths of macroscopic dark matter crossing the atmosphere.
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| 4. |
- Cooray, Vernon, 1952-, et al.
(författare)
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Electromagnetic fields of accelerating charges : Applications in lightning protection
- 2017
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Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 145, s. 234-247
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Tidskriftsartikel (refereegranskat)abstract
- Electromagnetic fields generated by accelerating charges can be utilized to evaluate the electromagnetic fields generated by systems where moving charges and/or propagating currents are present. The technique can be used easily to evaluate the electromagnetic fields generated by systems in which propagating currents are present. This is illustrated by utilizing the equations to derive expressions for the electromagnetic fields generated by systems in which current pulses injected by lightning flashes are propagating.
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| 5. |
- Cooray, Vernon, 1952-, et al.
(författare)
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Exact Expressions for Lightning Electromagnetic Fields : Application to the Rusck Field-to-Transmission Line Coupling Model
- 2023
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Ingår i: Atmosphere. - : MDPI. - 2073-4433 .- 2073-4433. ; 14:2
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Tidskriftsartikel (refereegranskat)abstract
- An exact analytical expression for the electric field of the return stroke as excited by a propagating step current source is derived in this paper. This expression could be advantageously used to evaluate the disturbances caused by lightning on overhead lines. There are three equivalent procedures to evaluate the voltages induced by lightning on power lines, namely, the Agrawal-Price-Gurbaxani model, the Taylor-Satterwhite-Harrison model, and the Rachidi model. In the case of a vertical return stroke channel, the coupling model developed by Rusck becomes identical to these three coupling models. Due to its simplicity, the Rusck model is frequently used by engineers to study the effects of lightning on power distribution and transmission lines. In order to reduce the time involved in the electromagnetic field calculation, the Rusck model is incorporated with an analytical expression for the electromagnetic fields of the return stroke excited by a propagating step current pulse. Our research work shows that the Rusck expression can be used to calculate the peak values of lightning induced voltages to an accuracy of about 10%. However, the use of this analytical expression to calculate the time derivatives of lightning induced voltages may result in errors as large as 50%. The derived expression in this paper can be used to correct for this inaccuracy. We also provide an exact expression for the electric field at any given point in space when the propagating current is an impulse function. This expression can be combined with the convolution integral to obtain the electric field corresponding to waveforms similar to measured return stroke currents.
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| 6. |
- Cooray, Vernon, 1952-, et al.
(författare)
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Generalized Electric Field Equations of a Time-Varying Current Distribution Based on the Electromagnetic Fields of Moving and Accelerating Charges
- 2019
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Ingår i: Atmosphere. - : MDPI. - 2073-4433 .- 2073-4433. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- In several studies conducted recently, it was shown that equations pertinent to the electric and magnetic fields produced by electrical charges in motion can be used to calculate the electromagnetic fields produced by current pulses propagating along linearly restricted paths. An example includes the case of current pulses propagating along conductors and conducting channels such as lightning. In this paper, it is shown how the technique can be applied to estimate the electromagnetic fields generated by current and charge distributions moving in arbitrary directions in space. The analysis shows that, depending on the way the problem is formulated using the field equations pertinent to accelerating charges, one procedure leads to the generalized dipole equations, which are independent of the velocity of propagation of the current, and the other procedure leads to a set of equations that depend on the velocity. Using the well-tested transmission line model of lightning return strokes as an example, it is shown that both sets of field equations give rise to the same total electromagnetic field.
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| 7. |
- Cooray, Vernon, 1952-, et al.
(författare)
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Ionization Waves Enhance the Production of X-rays during Streamer Collisions
- 2021
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Ingår i: Atmosphere. - : MDPI. - 2073-4433 .- 2073-4433. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data show that in laboratory sparks, X-rays are produced in time synchronization with the meeting of streamers of opposite polarity just before the final breakdown of the discharge gap. It has been suggested that the electric field enhancement created during the collision of streamers could provide the necessary conditions for electron acceleration, even though some of the theoretical studies show that the duration of the electric field is not long enough to do so. The experimental data on laboratory discharges show that. when streamers of opposite polarity meet each other, a potential or ionization wave that renders the streamer channels conducting is initiated. This paper shows that these ionization waves that convert the discharge channels from weakly conducting to highly conducting are associated with electric fields large enough to accelerate electrons to relativistic energies.
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| 8. |
- Cooray, Vernon, 1952-, et al.
(författare)
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Modeling Compact Intracloud Discharge (CID) as a Streamer Burst
- 2020
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Ingår i: Atmosphere. - : MDPI. - 2073-4433 .- 2073-4433. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- Narrow Bipolar Pulses are generated by bursts of electrical activity in the cloud and these are referred to as Compact Intracloud Discharges (CID) or Narrow Bipolar Events in the current literature. These discharges usually occur in isolation without much electrical activity before or after the event, but sometimes they are observed to initiate lightning flashes. In this paper, we have studied the features of CIDs assuming that they consist of streamer bursts without any conducting channels. A typical CID may contain about 10(9) streamer heads during the time of its maximum growth. A CID consists of a current front of several nanosecond duration that travels forward with the speed of the streamers. The amplitude of this current front increases initially during the streamer growth and decays subsequently as the streamer burst continues to propagate. Depending on the conductivity of the streamer channels, there could be a low-level current flow behind this current front which transports negative charge towards the streamer origin. The features of the current associated with the CID are very different from those of the radiation field that it generates. The duration of the radiation field of a CID is about 10-20 mu s, whereas the duration of the propagating current pulse associated with the CID is no more than a few nanoseconds in duration. The peak current of a CID is the result of a multitude of small currents associated with a large number of streamers and, if all the forward moving streamer heads are located on a single horizontal plane, the cumulative current that radiates at its peak value could be about 10(8) A. On the other hand, the current associated with an individual streamer is no more than a few hundreds of mA. However, if the location of the forward moving streamer heads are spread in a vertical direction, the peak current can be reduced considerably. Moreover, this large current is spread over an area of several tens to several hundreds of square meters. The study shows that the streamer model of the CID could explain the fine structure of the radiation fields present both in the electric field and electric field time derivative.
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| 9. |
- Cooray, Vernon, 1952-, et al.
(författare)
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On the Action of the Radiation Field Generated by a Traveling-Wave Element and Its Connection to the Time Energy Uncertainty Principle, Elementary Charge and the Fine Structure Constant
- 2017
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433 .- 2073-4433. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Recently, we published two papers in this journal. One of the papers dealt with the action of the radiation fields generated by a traveling-wave element and the other dealt with the momentum transferred by the same radiation fields and their connection to the time energy uncertainty principle. The traveling-wave element is defined as a conductor through which a current pulse propagates with the speed of light in free space from one end of the conductor to the other without attenuation. The goal of this letter is to combine the information provided in these two papers together and make conclusive statements concerning the connection between the energy dissipated by the radiation fields, the time energy uncertainty principle and the elementary charge. As we will show here, the results presented in these two papers, when combined together, show that the time energy uncertainty principle can be applied to the classical radiation emitted by a traveling-wave element and it results in the prediction that the smallest charge associated with the current that can be detected using radiated energy as a vehicle is on the order of the elementary charge. Based on the results, an expression for the fine structure constant is obtained. This is the first time that an order of magnitude estimation of the elementary charge based on electromagnetic radiation fields is obtained. Even though the results obtained in this paper have to be considered as order of magnitude estimations, a strict interpretation of the derived equations shows that the fine structure constant or the elementary charge may change as the size or the age of the universe increases.
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| 10. |
- Cooray, Vernon, 1952-, et al.
(författare)
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On the Apparent Non-Uniqueness of the Electromagnetic Field Components of Return Strokes Revisited
- 2021
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Ingår i: Atmosphere. - : MDPI. - 2073-4433 .- 2073-4433. ; 12:10
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Tidskriftsartikel (refereegranskat)abstract
- Recent research work shows that there are four procedures that can be used to calculate the electromagnetic fields from a current source. These different procedures, even though producing the same total field, give rise to field components that differ from one procedure to another. This has led to the understanding that the various field terms that constitute the total field cannot be uniquely determined. In this paper, it is shown that all four field expressions can be reduced to a single field expression, and the various field terms arising from acceleration, uniformly moving, and stationary charges can be uniquely determined. The differences in the field terms arising from different techniques are caused by the different ways of summing up the contribution to the total electric field coming from the accelerating, moving, and stationary charges.
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