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K and M changes in ...
K and M changes in close lightning ground flashes in Florida
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- Thottappillil, Rajeev, 1958- (author)
- University of Florida, Gainesville, USA
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- Rakov, Vladimir A. (author)
- University of Florida, Gainesville, USA
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- Uman, Martin A. (author)
- University of Florida, Gainesville, USA
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(creator_code:org_t)
- 1990
- 1990
- English.
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In: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 95:D11, s. 18631-18640
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Abstract
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- Electric field changes produced by K and M processes in Florida lightning ground flashes at distances within 12 km are analyzed and compared. The geometric-mean time durations were similar: 0.7 ms for 135 K changes and 0.9 ms for 80 M changes. The geometric-mean time intervals between events were dissimilar: 12.5 ms for 93 K change intervals and 2.1 ms for 48 M change intervals. Our geometric mean K change interval is about twice the median value observed by Kitagawa et al. (1962) in New Mexico who used a somewhat different measurement technique, while our geometric mean M change interval is about one-third the New Mexico median value although Kitagawa et al. (1962) apparently excluded from their statistical data those M components occurring within 15 ms of the return stroke initial peak field, and we included these. The K electric field changes were not always simple ramps superimposed on the slower interstroke J or final F field changes, but, rather, could be grouped into four general waveshape categories. All M field changes had relatively similar hooked shapes. We argue that the hypothesis proposed by Kitagawa et al. (1962) that K and M processes are essentially the same physical phenomenon is not supported by our data, although it cannot be positively ruled out; and, additionally, that the conclusion of Kitagawa and Brook (1960) that the net interstroke field change (J change) is essentially the sum of the individual K changes is also not supported by our data. Further, our data suggest that there is a significantly higher upper limit for the moment change associated with K processes in ground flashes than the 1 to 2 C-km reported by Brook and Kitagawa (1960) and Ogawa and Brook (1964).
Subject headings
- TEKNIK OCH TEKNOLOGIER -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)
Keyword
- Lightning
- Electromagnetic Compatibility
Publication and Content Type
- ref (subject category)
- art (subject category)
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