Fizika munja i grmljavine

master's thesis

• Title (english): Physics of lightning and and thunder
• Author: Nataša Gotal
• Mentor: Damir Pajić (mentor)
• Committee member: Damir Pajić (predsjednik povjerenstva)
• Committee member: Maja Planinić (član povjerenstva)
• Committee member: Nikola Poljak (član povjerenstva)
• Committee member: Davor Horvatić (član povjerenstva)
• Committee member: Damir Veža (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2014-07-18, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Strujni krug Zemlje je električni sistem građen kao sferni kondenzator sa dvije sferne koncentrične plohe, jedna je Zemljina površina, a druga je elektrosfera. Između njih nalazi se atmosfera kao dielektrik. U razdoblju lijepog vremena atmosfera je slabo vodljiva zbog djelomičnog ioniziranja atoma i molekula djelovanjem ultraljubičastog zračenja Sunca, kozmičkog zračenja i Zemljine radioaktivnosti. Između sfernih ploha postoji struja lijepog vremena od oko 1kA, ili 2pAm-2. Njome bi se sav naboj na Zemlji i u atmosferi mogao, ovisno o stupnju zagađenja zraka, neutralizirati u vremenskom intervalu od približno 10 minuta. Pretpostavlja se da oluje osiguravaju nadomještanje negativnog naboja na površini Zemlje stvarajući oborinske struje, struje korone i pražnjenja munjama. Postoji i ukupna struja od vrha oblaka prema elektrosferi veličine oko 0.5A po oluji. Stvaranjem jakog električnog polja, kod razvoja oluje, dio zraka postaje potpuno ionizirana plazma s temperaturom oko 30 000 K pa nastaje kanal električnog izboja koji zovemo munja. Zbog visoke temperature unutar kanala dolazi do povećanja tlaka, pa se zagrijani plin širi i izaziva stvaranje udarnog vala u zraku oko kanala. Okolni zrak stvara otpor valu i naglo ga prigušuje. Konačni efekt širenja i zgušnjavanja zraka je nastajanje valova zvuka koje zovemo grmljavina. Visoka temperatura unutar kanala električnog pražnjenja omogućuje fotokemijske reakcije pa je uočeno stvaranje reaktivnih dušikovih spojeva NOx koji utječu na klimatske promjene. Iako danas postoje različite mjerne tehnike i uređaji kojima se došlo do novih saznanja o munjama, teorijska predviđanja procesa koji omogućuju i iniciraju munje nisu potpuno potvrđena rezultatima promatranja i izvršenim mjerenjima. Istraživanje atmosferskog pražnjenja otežava prostorna i vremenska neodređenost udara munje. Razumijevanje mehanizama iniciranja munje u atmosferi, pomoglo bi i razvijanju boljih načina zaštite od udara. U metodičkom dijelu ovog rada prikazan je i jedan od načina kako se ova pojava može iskoristiti u nastavi.

Abstract (english)

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.

• Keywords: atmosferski tlak; oluja; munje; atmosferska fizika visokih energija; grmljavina
• Language: croatian
• URN:NBN: urn:nbn:hr:217:296132
• Study programme: Title: Physics; specializations in: Education; Course: Education; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra edukacije fizike (magistar/magistra edukacije fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-06-14 14:54:11