Basic discharge processes in the atmosphere
2012 (English)In: Lightning Electromagnetics / [ed] Vernon Cooray, IET , 2012, 65-85 p.Chapter in book (Refereed)
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.
Place, publisher, year, edition, pages
IET , 2012. 65-85 p.
Physical Sciences Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-190582DOI: 10.1049/PBPO062E_ch3ISBN: 978-1-84919-215-6OAI: oai:DiVA.org:uu-190582DiVA: diva2:583774