AN ANTENNA THEORY MODEL FOR THE LIGHTNING RETIJRN STROKE (original) (raw)
Related papers
On Representation of Lightning Return Stroke as a Lossy Monopole Antenna With Inductive Loading
IEEE Transactions on Electromagnetic Compatibility, 2000
In this paper, a modification of the antenna theory (AT) model of the lightning return stroke to include inductive loading is presented. The distributed inductive energy-storing elements are used in the modified AT model (designated as ATIL model, where IL stands for inductive loading) to control the propagation speed of the upward traveling current wave without using an artificial, higher permittivity dielectric medium, as done in the original AT model. The variation of the propagation speed along the channel is also considered in the proposed model. As in the original AT model, resistive loading is used to account for the current attenuation with height. Numerical solution of the electric field integral equation in the time domain using the method of moments with appropriate boundary conditions yields a time-space distribution of current along the lightning channel. This current distribution and the resultant electromagnetic fields for the ATIL model are compared with those predicted by other time-domain and frequency-domain electromagnetic models. The current distribution predicted by the ATIL model exhibits features (such as current dispersion) that are more consistent with optical observations of lightning compared to the predictions of the original AT model. Index Terms-Antenna theory (AT), current distribution, electric and magnetic fields, inductive loading, lightning return stroke modeling.
Analysis of Lightning-Radiated Electromagnetic Fields in the Vicinity of Lossy Ground
IEEE Transactions on Electromagnetic Compatibility, 2005
An antenna theory (AT) approach in the frequency domain is presented to compute electromagnetic fields radiated by a lightning return stroke. The lightning channel is modeled as a lossy-wire monopole antenna (a wire antenna with distributed resistance) energized by a current source at its base, and the ground is modeled as a lossy half-space. The method of moments is used for solving the governing electric field integral equation (EFIE) in the frequency domain. The resultant current distribution along the channel is used to calculate electromagnetic fields at different distances from the channel. All field components are evaluated using a rapid but accurate procedure based on a new approximation of Sommerfeld integrals. In contrast with the previous models, the approach proposed here is characterized by a self-consistent treatment of different field components in air or on the surface of a lossy half-space. It is shown that the omission of surface wave terms in the general field equations, as done in the perfect-ground approximation, can strongly affect model-predicted field components.
Electromagnetic models of the lightning return stroke
Journal of Geophysical Research, 2007
1] Lightning return-stroke models are needed for specifying the source in studying the production of transient optical emission (elves) in the lower ionosphere, the energetic radiation from lightning, and characterization of the Earth's electromagnetic environment, as well as studying lightning interaction with various objects and systems. Reviewed here are models based on Maxwell's equations and referred to as electromagnetic models. These models are relatively new and most rigorous of all models suitable for computing lightning electromagnetic fields. Maxwell's equations are numerically solved to yield the distribution of current along the lightning channel. Different numerical techniques, including the method of moments (MoM) and the finite difference time domain (FDTD) method, are employed. In order to achieve a desirable current-wave propagation speed (lower than the speed of light in air), the channel-representing wire is embedded in a dielectric (other than air) or loaded by additional distributed series inductance. Capacitive loading has been also suggested. The artificial dielectric medium is used only for finding the distribution of current along the lightning channel, after which the channel is allowed to radiate in air. Resistive loading is used to control current attenuation with height. In contrast with distributed circuit and so-called engineering models, electromagnetic return-stroke models allow a self-consistent full-wave solution for both lightning-current distribution and resultant electromagnetic fields. In this review, we discuss advantages and disadvantages of four return-stroke channel representations: a perfectly conducting/resistive wire in air, a wire embedded in a dielectric (other than air), a wire in air loaded by additional distributed series inductance, and a wire in air having additional distributed shunt capacitance. Further, we describe and compare different methods of excitation used in electromagnetic return-stroke models: closing a charged vertical wire at its bottom with a specified grounded circuit, a delta-gap electric field source, and a lumped current source. Finally, we review and compare representative numerical techniques used in electromagnetic modeling of the lightning return stroke: MoMs in the time and frequency domains and the FDTD method. We additionally consider the so-called hybrid model of the lightning return stroke that employs a combination of electromagnetic and circuit theories and compare this model to electromagnetic models. Citation: Baba, Y., and V. A. Rakov (2007), Electromagnetic models of the lightning return stroke,
New Approaches to Modeling of Lightning Electromagnetic Field
This paper presents the results of the research on lightning electromagnetic field calculations in time domain in the case of perfectly conducting ground, so as calculations in frequency domain of electromagnetic field radiated by mast antenna above real ground. It should be emphasized that several novel approaches during this research were introduced, includ-ing application of one new function for representing lightning return stroke channel-base current and one new model for spec-tral reflection coefficient for solving problems of the real ground parameters influence. INTRODUCTION In the first section of this paper the structure of light-ning electromagnetic field (LEMF) is numerically deter-mined directly in time domain using antenna theory ap-proach and thin wire approximation of the lightning chan-nel. Within modified transmission line model with expo-nential decay, as an engineering return stroke current model, one new suitable function is applied for the ap-proximation of cha...
American Journal of Applied Sciences, 2007
In this study we present and analysis of the return-stroke lightning current and described their models which existing in the literature by several authors for the evaluation of radiated electromagnetic fields and modelling the coupling with electrical systems based on the calculation of induced voltages. the objective of this work is to take part in the improvement of the coordination of electric insulations and to put device also for calculation of the over-voltages induced in the electrical networks by the indirect lightning strokes which represent the most dangerous constraint and most frequent. A comparative study between the existing models and the analysis of the parameters which affect the space and temporal behaviour of the current lightning strokes as well as the importance of the lightning current at the channel base form the essential consequence of this study.
Modeling of Lightning Strokes Using Two-Peaked Channel-Base Currents
International Journal of Antennas and Propagation, 2012
Lightning electromagnetic field is obtained by using “engineering” models of lightning return strokes and new channel-base current functions and the results are presented in this paper. Experimentally measured channel-base currents are approximated not only with functions having two-peaked waveshapes but also with the one-peaked function so as usually used in the literature. These functions are simple to be applied in any “engineering” or electromagnetic model as well. For the three “engineering” models: transmission line model (without the peak current decay), transmission line model with linear decay, and transmission line model with exponential decay with height, the comparison of electric and magnetic field components at different distances from the lightning channel-base is presented in the case of a perfectly conducting ground. Different heights of lightning channels are also considered. These results enable analysis of advantages/shortages of the used return stroke models acc...
Influence of Equivalent Lightning Discharge Channel Height on Electromagnetic Field
Using antenna theory approach and thin wire ap-proximation for lightning channel, the expressions for lightning electromagnetic field components are obtained directly in time domain. New suitable function for approximation of channel-base current is applied within one engineering lightning channel return-stroke current model. Function parameters are chosen so they provide desired characteristics of lightning electromagnetic pulse. The influence of equivalent lightning channel height on electromagnetic field components is presented in the paper.