Far-field measurements of lightning-produced electromagnetic fields are of high importance for lightning location systems. Data from recorded lightning strokes can be, for example, used to assess the risk of lightning-induced damage in some geographical areas. Artificially triggered lightning, usually generated using rocket-wire technology, plays an important role in the study of lightning physics. Multiple-station observations of far (typically larger than 20 km) electric field waveforms produced by rocket-triggered lightning are quite rare. In 2014, electric field waveforms were measured for return strokes through the rocket-and-wire technique at Conghua. They were measured by electric field sensors at nine sites belonging to the lightning locating system in Foshan, Guangzhou, China. A total of 38 events were recorded and overall statistics of those waveforms are presented. The results were compared to previous experimental data related to natural and artificially triggered lightning to validate their similarity.

This paper presents the observation results of the induced voltage at the terminal of a 10 kV distribution line with 40 m distance from nearby triggered lightning pole at Guangzhou in the Summer of 2018. It is shown that the induced voltage waveforms exhibit three components including a slow increase preceding the initial negative peak, following a rapid polarity reversal and attenuated oscillations. The characteristic waveform parameters are defined in this paper. The observed negative peak value voltage ranges from -47.1 kV to -7.5 kV. The positive peak value voltage ranges from 5.3 kV to 20.9 kV, and the peak to peak value voltage ranges from 12.8 kV to 63.2 kV. The test results show that the negative peak value voltage of the induced voltage at the terminal of distribution generated by nearby negative triggered lightning generally exceeds the positive peak value, and in some cases the negative peak value even reaches twice the positive peak value. The negative 10%-90% peak rise time ranges from 2.3 's to 88.5 μs, and the average oscillation period is about 18 μs for oscillation component. Both negative and positive peaks of induced voltage show good linear relationship with the lightning current.

In the summer of 2013, a three-dimensional (3D)-based Foshan Total Lightning Location System (FTLLS), embedded with differential time of arrival (DTOA) techniques, was installed and started its operation in Foshan, Guangdong Province, China. In this paper, the geographical distribution and set-up information of FTLLS, the estimated locating errors and locating results, as well as its initial operation results are presented. FTLLS consists of nine sub-stations that receive electromagnetic waves associated with lightning discharges and locates VLF/LF (200 Hz–500 kHz) radiation sources in 3D. The remote sub-stations acquired triggered waveforms with a duration of 0.5 ms, a resolution of 12-bits, and a GPS-based sferic time tags of 24 h per day. Cloud-to-ground (CG) lightning events, intra-cloud (IC) lightning events and narrow bipolar events (NBEs) were located by FTLLS. Based on the Monte Carlo simulation, the two-dimensional horizontal location error is basically less than 100 m, and the vertical error (altitude) is less than 200 m when the lightning event occurs within the network. On the other hand, over 14 million lightning strikes were recorded successfully by FTLLS during the period of May to October in 2014, among which IC events, CG events and NBEs accounted for 65%, 34% and 1%, respectively. It is shown that FTLLS is capable of a fine three-dimensional (3D) location, in which the altitude parameters obtained are reasonable and well consistent with observed data in the previous studies. The location results of thunderstorms were additionally verified through simultaneously-observed radar data.

The characteristics of optical and electric field waveforms from altitude triggered lightning flash at Guangzhou Field Experiment Site for Lightning Research and Testing (GFESLRT) during the summer of 2019 are presented. The altitude triggered lightning flash had eight return strokes with nine M‐components along four development paths. And the terminal heights of four paths are over 1,626 m above the ground. Our study presented an arithmetic mean of 0.62 kV/m and an arithmetic mean of 0.63 ms of half‐peak width for 16 initial continuous current (ICC) pulses values, as well as an arithmetic mean of 1.24 kV/m and an arithmetic mean of 0.47 ms of half peak width for nine M‐components values. The average 2‐D speed ranged from 3.80°× 10⁵ to 2.94 × 10⁶ m/s for the attempted leaders and from 1.26 × 10⁶ to 6.96 × 10⁶ m/s for the dart leaders. Basically, the greater the downward leader’s 2‐D propagation speed, the larger the electric field change. The electric field waveform in the rising edge of return stroke can be divided into three parts: “SF” indicates the slow front of the return stroke; “FT” indicates the fast transition of the return stroke; “SS” indicates shoulder structure of the return stroke. The arithmetic mean of SF electric field change is 1.45 kV/m and that of SF risetime is 110.6 μs. The arithmetic mean of the first FT electric field change is 4.71 kV/m and that of the first FT risetime is 1.1 μs. The arithmetic mean of the SS electric field change is 3.89 kV/m and that of the SS risetime is 28.1 μs.

Simultaneous measurements of current and multiple‐station electric fields associated with a 5.4‐kA‐peak M‐component in rocket‐triggered lightning are presented in this study. A close‐range electric field measurement site was located northeast of the triggering site, 195° clockwise from South, at a distance of 78 m, while the distant multiple stations in this study were located southwest of the lightning triggering site (25–48°, clockwise from South) at a distance ranging from 69 to 126 km. Both the fast microsecond‐scale and slow millisecond‐scale pulses were observed at six distant stations. At the close station, the fast pulse was not noticeable. The magnitude and half‐peak width of the fast pulse were in the range of 0.91–1.93 V/m and 2.0–3.0 μs, respectively. The corresponding parameters for the slow pulse were, respectively, in the range of 0.59–1.29 V/m and 20.0–25.1 μs. The time lag between the onset of the channel‐base current and the far electric field of the M‐component was 18 μs. This time lag was used to deduce the ratio of the M‐component channel length and the wave speed. The classical guided wave M‐component model proposed by Rakov et al. (1995,https://doi.org/10.1029/95JD01924) to simulate the slow, millisecond‐scale field pulse assumes that neither the incident nor the reflected current wave undergoes attenuation even though the wave propagation occurs along a lossy channel. A modified guided wave M‐component model is proposed in this study in which the M‐component current wave attenuates with an exponential decay. Based on the best agreement achieved between the simulated fields using the modified two‐wave M‐component model and the observed near and far electric fields, the channel length, the M‐component wave speed, and the current attenuation constant were inferred, respectively, as 1.8 km, 1 × 10⁸ m/s, and 3 km. It is shown that the modified guided wave M‐component model is able to reproduce reasonably well the electric fields both at close and far distance ranges.