Simulation of corona at lightning-triggering wire: Current, charge transfer, and the field-reduction effect

Abstract

[1] We have examined, using the finite difference time domain (FDTD) method for solving discretized Maxwell's equations, the effect of upward extending wire, used for artificial lightning initiation from natural thunderclouds, and corona space charge emanated from this wire on the close ground-level electric field (prior to lightning initiation). The wire current and charge transfer are also estimated. The lightning-triggering wire is assumed to be perfectly conducting and extending vertically upward with a constant speed of v = 150 m/s. Owing to the limitations of the FDTD method, the wire radius is set to r = 0.27 m, larger than the actual radius (0.1 mm), but the results are not expected to be much influenced by this assumption. The corona space charge that emanated from the wire surface is represented by a conducting cylindrical sheath of outer radius r = 2, 4, 8, and 16 m, coaxial with the wire (the dynamics of corona discharge are not considered here). Other geometries of the corona space charge sheath are considered as well. It has been found that the results presented here are insensitive to the value of corona sheath conductivity ranging from 10 −8 S/m to infinity. The corona space charge layer at the ground is simulated by perfectly conducting cylindrical tubes placed on the ground surface, coaxial with the upward extending conductor. The quasi-static electric field between the thundercloud charge source and the ground is simulated by creating a quasi-uniform, upward directed electric field of 43 kV/m between two parallel conducting plates limiting the FDTD computational domain. The simulated corona space charge at the ground reduced the electric field at the ground surface to 5.5 kV/m, a typical value at the time of rocket launch. The upward directed electric field E z on the ground surface in the vicinity of triggering wire decreases with increasing the altitude of the wire top. When the wire-top altitude is 200 m, the reduction of E z at horizontal distance d = 60 m is about 17, 26, 31, 40, and 52% relative to the background value of 5.5 kV/m for r = 0.27, 2, 4, 8, and 16 m, respectively, while the corresponding reduction of E z at d = 360 m in all cases is only 1% or less. The calculated results for r ≈ 4 to 16 m agree reasonably well with E z variations measured at d = 60 and 350 m from the triggering wire by Biagi et al. (2011). This indicates that the electric field reduction in the vicinity of triggering wire, prior to lightning initiation, is primarily caused by the presence of corona space charge emanated from the wire to a radius of about 4 m or more, as opposed to the presence of wire alone. The total charge transfer from the ground to the wire (whose top is at an altitude of 200 m) is 1.2, 4.5, 6.6, 9.5, and 14 mC for r = 0.27, 2, 4, 8, and 16 m, respectively. The corresponding currents flowing in the wire are 2.1, 7.9, 11, 15, and 22 mA. The model-predicted charges and currents for r = 2 to 4 m are consistent with limited measurements available in the literature, smaller than the values b...

Measurement and analysis of ground‐level electric fields and wire‐base current during the rocket‐and‐wire lightning triggering process

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A model for the evaluation of the electric field associated with the lightning-triggering rocket wire and its corona

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“…To perform the comparison with our analytical simulation, we have approximated the computed distribution of the background electric field shown in Figure 11a in Baba and Rakov [] as …”

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