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## [TowerTalk] modeling lightning

 To: "Towertalk" [TowerTalk] modeling lightning Jim Lux Thu, 04 Jan 2007 20:24:00 -0800
 ```For those looking for technical papers on modeling lightning and coupling to antennas.. Sorry, some don't have the abstracts. Pokharel03 ? Pokharel, R.K., Ishii, M., Baba, Y, ?Numerical EM Analysis of Lightning Induced Voltage over Ground of Finite Conductivity?, IEEE Trans EM Compat., v45, #4, Nov 2003, p651-656 Krider92 - Krider, E.P., ?On the electromagnetic fields, Poynting vector, and peak power radiated by lightning return strokes,? J. Geophys. Res., vol. 97, pp. 15,913-15,917, Oct. 1992. Abstract: The initial radiation fields, Poynting vector, and total electromagnetic power that a vertical return stroke radiates into the upper half space have been computed when the speed of the stroke, , is a significant fraction of the speed of light, c, assuming that at large distances and early times the source is an infinitesimal dipole. The initial current is also assumed to satisfy the transmission-line model with a constant and to be perpendicular to an infinite, perfectly conducting ground. The effect of a large is to increase the radiation fields by a factor of (1 2 cos2 ) 1, where = /c and is measured from the vertical, and the Poynting vector by a factor of (1 2 cos2 ) 2. This increase is just a few percent or less at small , but when =0.67, the fields are about 80% larger at small and 50% larger at =30°, and the power that is radiated is increased by 26%. When =0.5 and the peak current is 30 kA, typical values for negative first strokes, the peak power that is radiated into the upper hemisphere is 1.0×1010 W. Wait00 ?Wait, J.R, Hill, D.A., ?Ground wave of an idealized lightning return stroke?, IEEE Trans Ant Prop, v48, #9, pp1349-1353, Sep 2000 Abstract: We model a lightning return stroke by a vertical traveling wave of current with a complex propagation constant. The Sommerfeld-integral analysis is similar to that of a vertical electric dipole over a lossy earth except that the source is distributed in height. When the integration over the source current is performed analytically, an extra term appears in addition to the classical Sommerfeld attenuation function. This term is a result of the height-gain function of the distributed source due to an effective elevated height of the source dipole moment. In most eases of interest, the extra term is small and the height-gain function is not much larger than one. The results have application to remote sensing of lightning from a ground-based observer Ishii00 ? Ishii,M., Baba,Y.,?Advanced computational methods in lightning performance. The Numerical Electromagnetics Code (NEC-2)?, IEEE Power Engr Soc, Winter Meeting, 2000, v4, 23-27 Jan 2000, pp2419-2424 Clancy06 - Clancy, T.J.; Brown, C.G., Jr.; Ong, M.M.; Clark, G.A., ?Lightning protection certification for high explosives facilities at Lawrence Livermore National Laboratory?, IEEE Ant Prop Soc Intl Symp 2006, 9-14 July 2006, pp 1163-1166 Lupo00 - Lupo, G. Petrarca, C. Tucci, V. Vitelli, M., ?EM fields associated with lightning channels: on the effect of tortuosity and branching?, IEEE Trans EM Compat, v42, #4, pp 394-404, Nov 2000 Abstract: Usually the electric and magnetic fields associated with lightning have been computed by assuming the lightning current to be contained in a straight vertical channel of negligible cross section above a flat perfectly conducting plane. Such a model, which does not take into account that real lightning is characterized by tortuosity and branching, is not able to justify the fine structure of the fields radiated by lightning discharges whose time-domain behavior exhibits a jagged shape with remarkable spectral content in several bands of practical interest. In this work the effect of channel tortuosity and branching is investigated by adopting a suitable numerical technique. The discharge channel has been regarded as a fractal antenna whose associated EM field has been evaluated by superimposing the contribution of the single line radiators composing the whole channel. Such a field has been compared with that generated by a simple dipole antenna in order to study the influence of the fractal nature of the channel on the generated EM fields. The relationship between the fractal dimension of the discharge channel and the fractal dimension of the generated time domain EM fields has been considered and the influence played on such a relationship by the distance between EM source and observation point has also been studied by analyzing the fields evaluated at far and close distances Portela98 - Portela, C., ?Statistical distribution of parameters of lightning impulses in antennas and radar towers-practical application examples?, Electromagnetic Compatibility, 1998. 1998 IEEE International Symposium on ,24-28 Aug 1998, v1, pp254-264 _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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