Duration of Lightning Strokes and Occurrence of Multiple Strokes

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Norinder, Harald (2011)

It is shown that the total duration of lightning strokes, the occurrence of multiple strokes and the time interval between them are partially influenced when measurements are made on direct strokes to tall objects. By recording the radiated electromagnetic field of lightning discharges in antenna circuits with cathode ray oscillographs at great distances from the lightning paths it was possible to obtain extensive data on the variation characteristics of lightning. Special methods were developed in order to analyse the lightning discharges with regard to the sequence of multiple strokes and the slow moving after-variation. A comparison of the discharge characteristics of lightning in Sweden with corresponding results from lower latitudes leads to the assumption that the intensity of thunderstorms is greater in low latitudes than in high latitudes. This involves researches of a geophysical problem of greatest interest from different points of view.DOI: 10.1111/j.2153-3490.1950.tb00308.x
  • References (9)

    15- vations will probably not alter this general character.

    In fig. 18 is reproduced the percentage distribution curves of time intervals between the beginning of successive components. In this distribution the Swedish values [4]are of a pronounced shorter time variation type, and mostly approach to the curves I and 2. The values of 3, taken in South Africa, have pronounced time intervals of longer durations.

    In fig. 19 the percentage distribution of durations of lightning strokes is reproduced.

    There is no doubt that the influence of the tall objects upon the results cannot be neglected when the lightning mechanism and especially the time variation character of lightning discharges are considered. The differences in the curves of fig. 19are pronounced also when we are dealing with measurements where strokes to open ground are analysed. These differences must have another explanation. I am inclined to ascribe the differences to a certain extent to latitude effects, as indicated previously. I have not personally been in a position to investigate lightning discharges in countries situated at a more southerly latitude, but I have had many opportunities to observe thunderstorms visually in southern countries, both in Europe, Africa and North America. My personal impression is that the intensity of such thunderstorms at lower latitudes in most cases is at a much higher level than in Sweden.

    [I] WAGNERC, . F., M c CANNG,. D., 1944: Lightning Phenomena. Electrical Transmission and Distribution Reference Rook. Third Edition p. 291-324. Westinghouse Electric and Manufacturing Company, East Pittsburg.

    [ 2 ] NORINDEHR., 1949: On thc Measurement and Nature of Atmospherics Produccd by Electric Discharges in Snow Squalls and from other Phenomena. Teflits I , 2.

    [3] NORINDERH, ., DAHLEO,., 1946: Measurements by Frame Aerials of Current Variations in Lightning Discharges. Arkiv .for Mntematik, Astronomi orh Fysik.

    32, A-,S.

    [4] ACKERMAN0N., A,, 1937: A Cathode Ray Oscillograph with Norinder Relay. Lightning Reference Book p. 564. Amer. Inst. of Electrical Engineers, N e w York.

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