A New Approximate Method for Lightning-Radiated ELF/VLF Ground Wave Propagation over Intermediate Ranges

Hou, Wenhao; Zhang, Qilin; Zhang, Jinbo; Wang, Lei; Shen, Yuan

doi:10.1155/2018/9353294

Cited by 12 publications

(10 citation statements)

References 27 publications

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“…The FDTD (finite difference time domain method) computed result is an E-field signal 2200 km away from the assumed lightning position. The model settings of FDTD were consistent with Hou's paper [21]. Figure 7 shows the formal FDTD computed result and that with added white noise for decomposition.…”

Section: Results Of Fdtd Computing Lightning Signal With White Noisesupporting

confidence: 72%

Application of a Modified Empirical Wavelet Transform Method in VLF/LF Lightning Electric Field Signals

Dai

Zhou

et al. 2022

Remote Sensing

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In this paper, to realize a better adaptive method for the lightning electric field signal denoising, we firstly compared the decomposition results of three methods called the EMD (empirical mode decomposition), the CEEMDAN (complete ensemble empirical mode decomposition with adaptive noise), and the EWT (empirical wavelet transform) by artificial signals, respectively, and found that the EWT was better than the other two methods. Then, a MEWT (modified empirical wavelet transform) method based on the EWT was presented for processing the natural lightning signals data. By using our MEWT method, we processed three types of electric field signal data with different frequency bands radiated by the lightning step leader, the cloud pulse and the return stroke, respectively, and the VLF (very low frequency) lightning signals propagating different distances from 500 km to 3500 km, by using the data of the fast electric field change sensors from Nanjing Lightning Location Network (NLLN) in 2018 and the data of the fast electric field change sensors and the VLF electric antennas from the NUIST Wide-range Lightning Location System (NWLLS) in 2021. The results showed that our presented MEWT method could adaptively process different lightning signal data with different frequencies from the step leader, the cloud pulse, and the return stroke; for the lightning VLF signal data from 500 km to 3500 km, the MEWT also achieved a better noise reduction effect. After denoising the signal by using our MEWT, the detection ability of the fast electric field change sensor was improved, and more weak lightning signals could be identified.

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Section: Results Of Fdtd Computing Lightning Signal With White Noisesupporting

confidence: 72%

Application of a Modified Empirical Wavelet Transform Method in VLF/LF Lightning Electric Field Signals

Dai

Zhou

et al. 2022

Remote Sensing

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“…Figure 3 shows the ionospheric electron density profiles used in the FDTD model during the daytime and nighttime. Other model settings are consistent with that of Hou et al's paper [37,38]. However, it is enough to accurately identify the ground wave peak point of the measured data by using a waveform bank without considering the geomagnetic field, and we are only interested in the character of the waveform bank, but not the value peak.…”

Section: Sferic Waveform Bankmentioning

confidence: 63%

“…It is worth noting that we have not established a simulated waveform bank of intracloud lightning (IC), because it is difficult to observe the multistation synchronization data of the IC owing to the propagation effect for a ground-based long-range lightning location network. Other model settings are consistent with that of Hou et al's paper [37,38]. However, it is enough to accurately identify the ground wave peak point of the measured data by using a waveform bank without considering the geomagnetic field, and we are only interested in the character of the waveform bank, but not the value peak.…”

Section: Sferic Waveform Bankmentioning

confidence: 63%

Preliminary Application of Long-Range Lightning Location Network with Equivalent Propagation Velocity in China

Dai

Zhou

et al. 2022

Remote Sensing

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The equivalent propagation method adopts a variable propagation velocity in lightning location, minimizing the location error caused by various factors in the long-range lightning location network. To verify the feasibility of this method, we establish a long-range lightning location network in China. A new method is used to extract the ground wave peak points of the lightning sferics and is combined with the equivalent propagation velocity method for lightning location. By comparing with the lightning data detected by the lightning locating system called advanced direction and time-of-arrival detecting (ADTD) that has been widely used for tens of years in China, the feasibility of this method is initially verified. Additionally, it is found that the relative detection efficiency of our long-range lightning location network can reach 53%, the average location error is 9.17 km, and the detection range can reach more than 3000 km. The equivalent propagation method can improve the average location accuracy by ~1.16 km, compared with the assumed light speed of lightning-radiated sferic from the lightning stroke point to the observation station. The 50th percentile of the equal propagation velocity is 0.998c, which may be used in the long-range lightning location networks.

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“…For long‐distance propagation of sferics from lightning, the time delay of the ground wave peak is related to the propagation distance (e.g., Honma et al., 1998; Pessi et al., 2009; Shao & Jacobson, 2009; Zhou et al., 2021). Besides the ground conductivity, the Earth curvature is also an important factor that causes larger ground wave attenuation over long distances (Hou et al., 2018).…”

Section: Introductionmentioning

confidence: 99%

Coherency of Lightning Sferics

Bai

Füllekrug

2022

Radio Science

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Lightning discharges are natural phenomena that are able to generate energies up to several GJ (Rakov & Uman, 2006). The transient radio waves emitted by the lightning discharges are called "atmospherics", or "sferics" for short. These electromagnetic waves widely cover the frequency spectrum from ∼1 Hz to ∼300 MHz, with relatively large spectral amplitudes in the extremely low frequency (ELF) range and very low frequency (VLF) range and a relative maximum at ∼10 kHz (e.g., Burke & Jones, 1992;Taylor, 1960;Weidman & Krider, 1986). Another source of VLF electromagnetic waves is radio transmitters (Barr et al., 2000).Lightning discharges fall into two major categories: cloud-to-ground discharges (CGs) and in-cloud discharges (ICs), where the CGs exhibit much larger peak currents compared to the ICs (e.g., Betz et al., 2009;Fiser et al., 2010). Cloud-to-ground discharges can lead to serious hazards and are more relevant to human life than ICs. The peak current of CGs has been studied for the purpose of lightning protection (e.g., Chowdhuri et al., 2005;Schulz et al., 2016;Takami & Okabe, 2007;Visacro, 2004), and existing lightning location networks mainly aim at detecting cloud-to-ground discharges with the time-of-arrival (TOA) technique.The ionosphere (σ ≈ 10 −4 Sm −1 − 10 −2 Sm −1 ) and the earth's ground (σ ≈ 10 −3 Sm −1 ) form a natural wave guide with large conductivity boundaries, while the atmosphere in between exhibits a much lower conductivity. This wave-guide is able to guide the propagation of sferics (e.g.

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A New Approximate Method for Lightning-Radiated ELF/VLF Ground Wave Propagation over Intermediate Ranges

Cited by 12 publications

References 27 publications

Application of a Modified Empirical Wavelet Transform Method in VLF/LF Lightning Electric Field Signals

Application of a Modified Empirical Wavelet Transform Method in VLF/LF Lightning Electric Field Signals

Preliminary Application of Long-Range Lightning Location Network with Equivalent Propagation Velocity in China

Coherency of Lightning Sferics

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