Effect of Nearby Buildings on Electromagnetic Fields from Lightning

Mosaddeghi, A.; Pavanello, D.; Rachidi, F.; Rubinstein, Marcos; Zweiacker, P.

doi:10.2174/1652803400901010052

Cited by 22 publications

(7 citation statements)

References 8 publications

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“…It is known that the building on top of which the measuring sensors are located can affect the measured signals (Baba & Rakov, 2007b;Mosaddeghi et al, 2009). For example, Baba and Rakov (2007b) have shown that a 20m tall building can result in an enhancement factor of 1.5.…”

Section: Lightning Current and Electric Field Measuring Systemsmentioning

confidence: 99%

Electromagnetic Fields Associated With the M‐Component Mode of Charge Transfer

Rachidi

Azadifar

et al. 2019

JGR Atmospheres

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In upward flashes, charge transfer to ground largely takes place during the initial continuous current (ICC) and its superimposed pulses (ICC pulses). ICC pulses can be associated with either M‐component or leader/return‐stroke‐like modes of charge transfer to ground. In the latter case, the downward leader/return stroke process is believed to take place in a decayed branch or a newly created channel connected to the ICC‐carrying channel at relatively short distance from the tower top, resulting in the so‐called mixed mode of charge transfer to ground. In this paper, we study the electromagnetic fields associated with the M‐component charge transfer mode using simultaneous records of electric fields and currents associated with upward flashes initiated from the Säntis Tower. The effect of the mountainous terrain on the propagation of electromagnetic fields associated with the M‐component charge transfer mode (including classical M‐component pulses and M‐component‐type pulses superimposed on the initial continuous current) is analyzed and compared with its effect on the fields associated with the return stroke (occurring after the extinction of the ICC) and mixed charge transfer modes. For the analysis, we use a 2‐Dimentional Finite‐Difference Time Domain method, in which the M‐component is modeled by the superposition of a downward current wave and an upward current wave resulting from the reflection at the bottom of the lightning channel (Rakov et al., 1995, https://doi.org/10.1029/95JD01924 model) and the return stroke and mixed mode are modeled adopting the MTLE (Modified Transmission Line with Exponential Current Decay with Height) model. The finite ground conductivity and the mountainous propagation terrain between the Säntis Tower and the field sensor located 15 km away at Herisau are taken into account. The effects of the mountainous path on the electromagnetic fields are examined for classical M‐component and M‐component‐type ICC pulses. Use is made of the propagation factors defined as the ratio of the electric or magnetic field peak evaluated along the mountainous terrain to the field peak evaluated for a flat terrain. The velocity of the M‐component pulse is found to have a significant effect on the risetime of the electromagnetic fields. A faster traveling wave speed results in larger peaks for the magnetic field. However, the peak of the electric field appears to be insensitive to the M‐component wave speed. This can be explained by the fact that at 15 km, the electric field is still dominated by the static component, which mainly depends on the overall transferred charge. The contribution of the radiation component to the M‐component fields at 100 km accounts for about 77% of the peak electric field and 81% of the peak magnetic field, considerably lower compared to the contribution of the radiation component to the return stroke fields at the same distance. The simulation results show that neither the electric nor the magnetic field propagation factors are very sensitive to the risetimes of...

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Section: Lightning Current and Electric Field Measuring Systemsmentioning

confidence: 99%

Electromagnetic Fields Associated With the M‐Component Mode of Charge Transfer

Rachidi

Azadifar

et al. 2019

JGR Atmospheres

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“…: Finally, it is well known that the presence of the building on which the field sensors are located might affect the measured waveform (e.g., [37] and [38]). In particular, the electric field measured on the roof of a building might experience an enhancement that depends on several factors related to the building (shape, material, presence of conducting beams, etc.)…”

Section: ) Presence Of the Building On Which The Field Sensor Ismentioning

confidence: 99%

On Lightning Electromagnetic Field Propagation Along an Irregular Terrain

Azadifar

Rachidi

et al. 2016

IEEE Trans. Electromagn. Compat.

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Abstract-In this paper, we present a theoretical analysis of the propagation effects of lightning electromagnetic fields over a mountainous terrain. The analysis is supported by experimental observations consisting of simultaneous records of lightning currents and electric fields associated with upward negative lightning flashes to the instrumented Säntis tower in Switzerland. The propagation of lightning electromagnetic fields along the mountainous region around the Säntis tower is simulated using a full-wave approach based on the finite-difference time-domain method and using the two-dimensional topographic map along the direct path between the tower and the field measurement station located at about 15 km from the tower. We show that, considering the real irregular terrain between the Säntis tower and the field measurement station, both the waveshape and amplitude of the simulated electric fields associated with return strokes and fast initial continuous current pulses are in excellent agreement with the measured waveforms. On the other hand, the assumption of a flat ground results in a significant underestimation of the peak electric field. Finally, we discuss the sensitivity of the obtained results to the assumed values for the return stroke speed and the ground conductivity, the adopted return stroke model, as well as the presence of the building on which the sensors were located.

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“…As can be seen in Figures 6a and 6b, the vertical component of the electric field waveforms predicted by the proposed model is more consistent with the measurement data from the point of view of the field's higher peak, trend and late time values. However, both extensions of the AT model have still a high difference in level with the measured values, that is significantly larger than the simulation predictions, this effect can be ascribed to the building enhancement effect that is discussed by Pavanello et al [2007a, 2007b], Baba and Rakov [2007b], and Mosaddeghi et al [2009]. The main feature of the proposed model is demonstrated in the case of far distance (Figure 6c) where, as opposed to the ATIL‐F model, a zero crossing time of 42.85 μ s in distance of 50 km is reproduced in the predicted vertical electric and the azimuthal magnetic field waveforms.…”

Section: Simulation Resultsmentioning

confidence: 78%

Application of the nonlinear antenna theory model to a tall tower struck by lightning for the evaluation of return stroke channel current and radiated electromagnetic fields

Moosavi¹,

Moini²,

Sadeghi³

et al. 2011

J. Geophys. Res.

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[1] In this paper an improved antenna theory (AT) model with nonlinearly varying resistive loading and fixed inductive loading is used to electromagnetically simulate lightning strikes to tall structures. Measurement data captured from Toronto's CN tower are used to verify the validity of the new model. Both the return stroke channel (RSC) and the tower are modeled by straight thin conducting wires. The wire model of the channel is assumed to have distributed nonlinear resistive elements as a function of current and time, adopted from the numerical models of a spark channel and consequent shockwave from a lightning discharge, yielding a varying value of the channel radius from the base to the cloud along the RSC. Such distributed elements are used to take into account the current attenuation while propagating along the channel and varying propagation speeds lower than the speed of light. RSC current distribution and radiated electromagnetic fields in near, intermediate, and far range distances predicted by the proposed model are compared with those obtained from the measurement data and with those of the original AT model and the AT with fixed inductive loading (ATIL-F) model. Current wave propagation speed profile in RSC and tower is investigated as a function of height as well. The effects of applying different tower geometry models are also studied. It is shown that the new model is able to reproduce one of the characteristic features of the electromagnetic fields radiated by lightning, namely, the far-field inversion of polarity with a zero crossing occurring in the tens of microseconds range. We have also investigated the effect of nonlinearity of the channel assumed in the new model. It is shown that among the electromagnetic models, distributed nonlinear resistance along the channel leads to a zero crossing in the tens of microseconds range even for large values of resistance. It is also shown that decreasing the nonlinearity results in the predictions asymptotically converging to those of the ATIL-F model in which a uniformly distributed resistance along the channel is used. Further, the profile of the return stroke current attenuation and speed and removed charge as a function of height are investigated. Finally, the effect of lossy ground is analyzed using Wait-Cooray convolution formula in the time domain to verify the validity of PEC assumption in the proposed model.

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Effect of Nearby Buildings on Electromagnetic Fields from Lightning

Cited by 22 publications

References 8 publications

Electromagnetic Fields Associated With the M‐Component Mode of Charge Transfer

Electromagnetic Fields Associated With the M‐Component Mode of Charge Transfer

On Lightning Electromagnetic Field Propagation Along an Irregular Terrain

Application of the nonlinear antenna theory model to a tall tower struck by lightning for the evaluation of return stroke channel current and radiated electromagnetic fields

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