On the accuracy of approximate techniques for the evaluation of lightning electromagnetic fields along a mixed propagation path

Abstract

[1] In this paper we review simplified analytical expressions derived by Wait using the concept of attenuation function for the analysis of the propagation of lightning-radiated electromagnetic fields over a mixed propagation path (vertically stratified ground). Two different formulations proposed by Wait that depend on the relative values of ground surface impedances are discussed. It is shown that both formulations give nearly the same results for the time domain electric field. However, depending on the values of the normalized surface impedance for each ground section, the use of one of the two formulations is computationally more efficient. The accuracy of the Wait formulations was examined taking as reference full-wave simulations obtained using the finite difference time domain technique. It is shown that Wait's simplified formulas are able to reproduce the distant field peak and waveshape with a good accuracy.Citation: Shoory, A., A. Mimouni, F. Rachidi, V. Cooray, and M. Rubinstein (2011), On the accuracy of approximate techniques for the evaluation of lightning electromagnetic fields along a mixed propagation path, Radio Sci., 46, RS2001,

On Lightning Electromagnetic Field Propagation Along an Irregular Terrain

“…Note that we have considered a simple, homogeneous model for the ground with constant, frequencyindependent electrical parameters. A more thorough analysis taking into account the soil inhomogeneity (e.g., [7] and [13]) and frequency dependence (e.g., [17], [34], and [53]) is beyond the scope of this paper.…”

Validation and revision of far-field-current relationship for the lightning strike to electrically short objects

“…The attenuation of the initial radiation field resulting from the propagation over finitely conducting ground strongly depends on the current risetime, the object height, the ground conductivity and so on. When the lightning strikes tall objects, the high frequency content increases due to the transient process, the corresponding attenuation will become more seriously, because of the selective attenuation of the high frequency components along the finitely conducting ground (e.g., Rubinstein, 1996;Cooray, 1987Cooray, , 2003Cooray, , 2008Cooray, , 2009Cooray and Ming, 1994;Cooray and Perez, 1994;Cooray et al, 2000;Delfino et al, 2008aDelfino et al, , 2008bShoory et al, 2011aShoory et al, , 2011bZhang et al, 2012aZhang et al, , 2012bZhang et al, , 2012cZhang et al, , 2012dZhang et al, , 2013Li et al, 2013Li et al, , 2014. As a result, the peak and peak derivatives of the electromagnetic radiation fields far away from a lightning strike point may deviate from their ideal values.…”

“…Based on the azimuthal magnetic field on the perfectly conducting ground as depicted above, the propagation effect of the finite conductivity of the earth can be computed as below (e.g., Shoory et al, 2011aShoory et al, , 2011bCooray and Ming, 1994;Zhang et al, 2012aZhang et al, , 2012bZhang et al, , 2012cZhang et al, , 2012dZhang et al, , 2013Li et al, 2013Li et al, , 2014.…”

On validation of FCCFs for lightning striking tall objects considering propagation effect of finitely conducting earth

“…1(a), for a 300-m-high object (h=300 m), four current waveforms are also characterized by the same peak value (12 kA), but with different values for RT=0.5s(0.5h/c), RT=1.0s(1.0h/c), RT=1.5s(1.5h/c) , RT=2.0s(2.0h/c), as shown in Fig. 1 Based on the azimuthal magnetic field on the perfectly conduting ground as depicted above, the propagation effect of the finitely conducting earth can be computed as below [27] [28]:…”