| 1. |
- Cooray, Vernon, et al.
(författare)
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On the possible mechanism of keraunographic markings on lightning victims
- 2015
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 136:Part A, s. 119-123
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Tidskriftsartikel (refereegranskat)abstract
- During a lightning strike to a human the high electric field that exists at the point of contact of the lightning flash can generate electrical discharges known as streamer discharges along the skin. Previous research work has shown that the electric field at the head of these streamer discharges are large enough to accelerate electrons to relativistic speeds. In this paper it is shown that the streamers propagating along the skin will bombard the skin with energetic electrons. In this paper an estimation of the energy dissipated by these energetic electrons on the skin is estimated. Since beta radiation generated by radioactive substances consists of energetic electrons the effects of the energetic electrons generated by streamer discharges would be similar to the effects caused by low level beta radiation. It is suggested that the feather like marks, called keraunographical marks, that is sometimes observed on the skin of lightning victims is a result of superficial radiation injury with following inflammation in the epidermis and superficial layers of the dermis caused by energetic electrons.
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| 2. |
- Cooray, Gerald, et al.
(författare)
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Application of electromagnetic fields of an accelerating charge to obtain the electromagnetic fields of a propagating current pulse
- 2012
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Ingår i: Lightning Electromagnetics. - : IET. - 9781849192156 ; , s. 55-65
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Bokkapitel (refereegranskat)abstract
- It was recently demonstrated that electromagnetic fields from accelerating charges can be utilized to evaluate the electromagnetic fields from lightning return strokes. It was documented in detail how to utilize the equations to calculate electromagnetic fields of various engineering return stroke models, both current propagation and current generation types.It was also demonstrated how the equations can be utilized to calculate radiation fields generated by currents propagating along transmission lines in the presence of bends. The basics of this technique are summarized in this chapter by applying it to evaluate the electromagnetic fields of a propagating current pulse.
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| 3. |
- Cooray, Gerald, et al.
(författare)
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Could Some Ball Lightning Observations be Optical Hallucinations Caused by Epileptic Seizures?
- 2008
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Ingår i: The Open Atmospheric Science Journal. - 1874-2823. ; 2, s. 101-105
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Cooray, Gerald, et al.
(författare)
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Electromagnetic fields of a short electric dipole in free space - revisited
- 2012
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Ingår i: PROG ELECTROMAGN RES. - 1559-8985. ; 131, s. 357-373
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Tidskriftsartikel (refereegranskat)abstract
- Maxwell's equations specify that electromagnetic radiation fields are generated by accelerating charges. However, the electromagnetic radiation fields of an accelerating charge are seldom used to derive the electromagnetic fields of radiating systems. In this paper, the equations pertinent to the electromagnetic fields generated by accelerating charges are utilized to evaluate the electromagnetic fields of a current path of length l for the case when a pulse of current propagates with constant velocity. According to these equations, radiation is generated only at the end points of the channel where charges are being accelerated or decelerated. The electromagnetic fields of a short dipole are extracted from these equations when r >> l, where r is the distance to the point of observation. The speed of propagation of the pulse enters into the electromagnetic fields only in the terms that are second order in l and they can be neglected in the dipole approximation. The results illustrate how the radiation fields emanating from the two ends of the dipole give rise to field terms varying as 1/r and 1/r(2), while the time-variant stationary charges at the ends of the dipole contribute to field terms varying as 1/r(2) and 1/r(3).
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| 5. |
- Cooray, Vernon, 1952-, et al.
(författare)
-
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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| 6. |
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| 7. |
- Cooray, Vernon, et al.
(författare)
-
Basic electromagnetic theory - a summary
- 2012
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Ingår i: Lightning Electromagnetics. - : The Institution of Engineering and Technology. - 9781849192156
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Bokkapitel (refereegranskat)abstract
- The goal of this chapter is to provide a summary of the basic concepts of electro- magnetic theory as a complement to the subject matter, most of which is related to electromagnetism, discussed in this book. The chapter covers only the concepts that are necessary to understand the electromagnetics of lightning flashes.
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| 8. |
- 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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| 9. |
- Cooray, Vernon, et al.
(författare)
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Corona currents generated from a person’s head in the vicinity of lightning strikes : Stimulation ofphosphenes
- 2011
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Ingår i: 7th Asia-Pacific International Conference on Lightning.
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Konferensbidrag (refereegranskat)abstract
- Phosphene is a sensory experience which occurs dueto the interaction of electric currents generated by an externalagent with the visual cortex or retina. Occurrence of phospheneshas been documented in clinical Transcranial MagneticStimulation (TMS) studies where electric fields are induced inthe brain by the application of time varying magnetic fields. Inthis paper the possibility of creating phosphenes by the coronacurrents developing from the head of a person located close to alightning strike is investigated. The results show that themagnitude of the electric fields induced in the brain by coronacurrents are comparable to those generated by TMS. This inturn shows that the corona currents generated by long durationlightning flashes could excite phosphenes through theirinteraction with the visual cortex or retina in a human located inthe vicinity of the lightning channel. It is suggested that some ofthe ball lightning observations reported in the literature could beluminous perceptions caused by the interaction of the coronacurrents with the visual cortex or retina of a person located inthe vicinity of a lightning strike.
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| 10. |
- Cooray, Vernon, 1952-, et al.
(författare)
-
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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