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Measurements of NOx produced by rocket-triggered lightning
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research. (Åskforskning)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research. (Åskforskning)
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2007 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 3, p. L03816-Article in journal (Refereed) Published
Abstract [en]

We present the first direct measurements of NOx generated by specific lightning sources. In July 2005, three negative lightning flashes were triggered using the rocket-and-wire technique at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The NOx produced by these three rocket-triggered flashes was measured. The NOx production per unit charge was between 2 and 3 · 1020 molecules per meter per coulomb. The data show that the NOx production is primarily from long-duration, steady currents, as opposed to microsecondscale impulsive return stroke currents. This observation implies that cloud discharges, which transfer, via a steady current of the order of 100 A, larger charges than ground discharges, but do not contain return strokes, are as efficient as (or more efficient than) cloud-to-ground discharges in producing NOx.

 

Place, publisher, year, edition, pages
2007. Vol. 34, no 3, p. L03816-
National Category
Meteorology and Atmospheric Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Atmospheric Discharges; Electricity, Esp The Study Of Transients and Discharges
Identifiers
URN: urn:nbn:se:uu:diva-93605DOI: 10.1029/2006GL027956ISI: 000244360200001OAI: oai:DiVA.org:uu-93605DiVA, id: diva2:167133
Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2017-12-14
In thesis
1. NOx Production by Ionisation Processes in Air
Open this publication in new window or tab >>NOx Production by Ionisation Processes in Air
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study presented in this thesis was motivated by the large uncertainty on the concentration of atmospheric electrical discharges to the global nitrogen budget. This uncertainty is partly due to the fact that information concerning the NOx production efficiency of electrical discharges having current signatures similar to those of lightning flashes is not available in the literature. Another reason for this uncertainty is the fact that energy is used as a figure of merit in evaluating NOx production from lightning flashes even though insufficient knowledge is available concerning the energy dissipation in lightning flashes. The third reason for this uncertainty is the lack of knowledge concerning the contribution of discharge processes other than return strokes to the NOx production in the atmosphere. Lightning is not the only process in the atmosphere that causes ionisation and dissociation of atmospheric air. Cosmic rays continuously bombard the Earth with high energetic particles and radiation causing ionization and dissociation of air leading to the production of NOx in the atmosphere. The work carried out in this thesis is an attempt to improve the current knowledge on the way in which these processes contribute to the global NOx production. Experiments have been conducted in this thesis to estimate the NOx production efficiency of streamer discharges, laser-induced plasma, laboratory sparks having current signatures similar to those of lightning flashes, alpha particle impact in air and finally with the lightning flash itself. The results obtained from laboratory electrical discharges show the following: (a) The NOx production efficiency, in terms of energy, of positive streamer discharges is more or less similar to those of hot discharges. (b) The NOx production efficiency of an electrical discharge depends not only on the energy but also on the peak and the shape of the current waveform. (c) The current signature is a better figure of merit in evaluating the NOx yield of electrical discharges. As a part of this thesis work a direct measurement of NOx generated by lightning flashes was conducted and the results show that slow discharge processes such as continuing currents could be the main source of NOx in lightning flashes. Concerning NOx production by other ionisation processes such as alpha particle impacts in the atmosphere, the data gathered in this thesis show that each ionising event in air leads to the creation of one NOx molecule. In terms of energy the NOx production efficiency of alpha particles is similar to that of electrical discharges. The theoretical studies conducted within this thesis indicate that M-components contribute more than the return strokes to the NOx production. The calculations also show that the contribution to the global NOx budget by return stroke is not as high as that assumed in the current literature.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. p. 35
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 104
Keywords
Engineering physics, Nitrogen oxides, Lightning, Electrical Discharges, Cosmic Rays, Troposphere, Teknisk fysik
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:uu:diva-6016 (URN)91-554-6370-3 (ISBN)
Public defence
2005-10-28, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00
Opponent
Supervisors
Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2016-04-29Bibliographically approved

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Rahman, MahbuburCooray, Vernon

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