Physics of lightning and thunder

Gotal, Nataša (2014) Physics of lightning and thunder. Diploma thesis, Faculty of Science > Department of Physics.

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Abstract

The global electrical circuit is electrical system built like spherical condenser with two concentric spherical surfaces, one is Earth's surface, the other is electrosphere. The dielectric atmosphere is between them. In fair-weather regions atmosphere has low conductivity cause of partially ionization of atoms and molecules with cosmic radiation, ultraviolet radiation from the Sun and Earth's natural radioactivity. There is a fair weather current about 1kA, or 2pAm-2 between spherical surfaces. This current could neutralize, depending on atmospheric poluttion, in about 10 min. all charge on Earth and in atmosphere. It assumes the thunderstorms insure replacement of negative charges on the Earth's surface through precipitation current, corona discharges and lightning. There is integrated upward current about 0.5 A/thunderstorm from the top part of the thundercloud to electrosphere. Developed thunderstorm generates strong electric field, therefore a part of air becomes fully ionized plasma with temperature about 30 000 K and result in electrical discharge channel that is called lightning. The pressure raises inside of channel cause of high temperature, so heated gas expands and generates shock waves into the surrounding air. Air resistance damps the wave rapidly. Finally effect from propagation and inspissation of air is production of sound waves that are called thunder. High temperature within electrical discharge channel enables photochemical reactions that produces reactive nitrogen oxides NOx with influences on global climate change. Today are in use various experimental techniques and devices that have allowed great advences in our understanding of lightning. However theoretical presumptions of mechanisms that allow and initiate the lightning are not fully confirmed with measuring data yet. Atmospheric discharge research is difficult cause of spatial and time uncertainty of lightning discharge. If we better understand the mechanism of lightning initiation in the atmosphere, we'll be able to develop enhanced methods of lightning protection too. In the methodical part this paper presents one method how to use this phenomenon in theaching of physics.

Item Type: Thesis (Diploma thesis)
Keywords:
Supervisor: Pajić, Damir
Date: 18 July 2014
Subjects: NATURAL SCIENCES > Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 02 Sep 2014 13:16
Last Modified: 06 Oct 2014 13:34
URI: http://digre.pmf.unizg.hr/id/eprint/2590

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