| 1. |
- 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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| 2. |
- Cooray, Vernon
(författare)
-
Attachment of lightning flashes to grounded structures
- 2012
-
Ingår i: Lightning Electromagnetics. - : IET. - 9781849192156 ; , s. 765-787
-
Bokkapitel (refereegranskat)abstract
- A grounded structure can interact with a lightning flash in two different ways. It can interact with either a downward or an upward lightning flash. The initiation of a downward lightning flash takes place in the cloud, whereas in the case of upward lightning flash, the point of initiation is usually at the tip of a tall structure. In other words, upward lightning flashes are created by the grounded structure itself. In this chapter, a brief description of various models used to study the lightning attachment is given together with some of their predictions.
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| 3. |
- Cooray, Vernon
(författare)
-
Basic discharge processes in the atmosphere
- 2012
-
Ingår i: Lightning Electromagnetics. - : IET. - 9781849192156 ; , s. 65-85
-
Bokkapitel (refereegranskat)abstract
- The main constituents of air in the Earth's atmosphere are nitrogen (78%), oxygen (20%), noble gases (1%), water vapour (0.03%), carbon dioxide (0.97%) and other trace gas species. In general, air is a good insulator and it can maintain its insulating properties until the applied electric field exceeds about 2.8 x 104 V/cm at standard atmospheric conditions (i.e. T= 293 K and P =1 atm). When the background electric field exceeds this critical value, the free electrons in air generated mainly by the high energetic radiation of cosmic rays and radio active gases generated from the Earth start accelerating in this electric field and gain enough energy between collisions with atoms and molecules to ionize other atoms. This cumulative ionization leads to an increase in the number of electrons initiating the electrical breakdown of air. The threshold electric field necessary for electrical breakdown of air is a function of atmospheric density. When the leaders reach an electrode of opposite polarity or a region of opposite charge density, a rapid neutralization of the charge on the leader takes place. This neutralization process is called a return stroke. The exact mechanism of the return stroke is not yet known, but different types of models have been developed to describe them. These models are described in several chapters of this book. Here, we will concentrate on the four discharge processes mentioned above. Some parts of this chapter are adopted and summarized from Reference 1 where an extensive description of basic physics of discharges is given.
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| 4. |
- Cooray, Vernon, et al.
(författare)
-
Basic electromagnetic theory - a summary
- 2012
-
Ingår i: Lightning Electromagnetics. - : The Institution of Engineering and Technology. - 9781849192156
-
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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| 5. |
- Cooray, Vernon, et al.
(författare)
-
Excitation of visual sensory experiences by electromagnetic fields of lightning
- 2012
-
Ingår i: Lightning Electromagnetics. - : IET. - 9781849192156
-
Bokkapitel (refereegranskat)abstract
- In this chapter, we will consider the possible interactions, either direct or indirect, of the lightning-generated electromagnetic fields with the brain or the visual system of humans to induce visual sensations. Some of these visual sensations are known as phosphenes in the medical literature. Since some of these visual sensations could be misinterpreted as ball lightning, this subject is of interest for lightning researchers due to the still unsolved problem of the origin of ball lightning.
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| 6. |
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| 7. |
- Cooray, Vernon, et al.
(författare)
-
On the NOx generation in Corona, streamer and low-pressure electrical discharges
- 2012
-
Ingår i: Lightning Electromagnetics. - : Institution of Engineering and Technology. - 9781849192163 - 9781849192156 ; , s. 789-797
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- An assessment of the global distribution of nitrogen oxides (NOx) is required for a satisfactory description of tropospheric chemistry and in the evaluation of the global impact of increasing anthropogenic emissions of NOx. In the mathematical models utilized for this purpose, it is necessary to have the natural as well as man-made sources of NOx in the atmosphere as inputs. Thunderstorms are a main natural source of NOx in the atmosphere and it may be the dominant source of NOx in the troposphere in equatorial and tropical South Pacific.
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| 8. |
- Cooray, Vernon
(författare)
-
On the various approximations to calculate lightning return stroke-generated electric and magnetic fields over finitely conducting ground
- 2012
-
Ingår i: Lightning Electromagnetics. - : IET. - 9781849192156 ; , s. 427-484
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Bokkapitel (refereegranskat)abstract
- The exact solution to the electromagnetic fields generated by electric dipoles located above a finitely conducting ground plane was obtained by Sommerfeld. He presented his results in the form of a set of integrals. Since the numerical solutions of these integrals are time-consuming, attempts have been made to find approximate solutions to these integrals. In this chapter, various approximate solutions and procedures that have been used to calculate electromagnetic fields of return strokes over finitely conducting ground will be presented together with their limits of validity.
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| 9. |
- Cooray, Vernon
(författare)
-
Return stroke models for engineering applications
- 2012
-
Ingår i: Lightning Electromagnetics. - : The Institution of Engineering and Technology. - 9781849192156 ; , s. 231-261
-
Bokkapitel (refereegranskat)abstract
- In this chapter, we will describe and discuss several engineering models that can be utilized either to evaluate electromagnetic fields from lightning flashes or to study the direct effects of lightning attachment to various structures including tall towers. We will start by describing the basic concepts of engineering return stroke models. This discussion will be followed by a description of various return stroke models and the equations necessary for the evaluation of electromagnetic fields using these return stroke models.
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| 10. |
- Fernando, Mahendra, et al.
(författare)
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Measurements of lightning-generated electromagnetic fields
- 2012
-
Ingår i: Lightning Electromagnetics. - : IET. - 9781849192156 ; , s. 567-581
-
Bokkapitel (refereegranskat)abstract
- The vertical component of the electric field generated by lightning flashes can be measured either using a field mill or using a flat plate (or a vertical whip) antenna ; each method having its advantages and disadvantages. The three components of the electric field can be measured by using specially adapted spherical antennas.
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