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(a) The original spectra and the channel images of lightning A and B. (b) Pictures show the dart leader development of the subsequent return stroke (R1) for lightning B. (c) The spectral graph at a channel height of lightning A and B.
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Two positive cloud‐to‐ground lightning spectra have been captured by a slit‐less spectrograph. In combination with the synchronous electric field change waveshape, the discharge characteristics along the channel have been investigated. The results show that the total intensity of ionic lines in spectra and the electrical conductivity increase with...
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Temperature is one of the crucial parameters reflecting the energy and current transfer characteristics in lightning discharge plasma channels. According to the spectra of six lightning return strokes discharges recorded simultaneously by two high-speed slit-less spectrographs with different time resolutions, the spectral intensity and temperature...
Citations
... 2 An et al. also calculated the conductivity of the lightning and found that the temperature and conductivity should mainly depend on the discharge intensity and should not be affected by the direction of the channel current. 13 Furthermore, some transport characteristics of lightning channels, such as thermal conductivity (k e ) and thermal diffusivity (D T e ), are also associated with the channel current of lightning. 2,4,14 Thermal conductivity describes the transfer of thermal energy caused by thermal gradients in the plasma and the presence of chemical reactions, while thermal diffusivity indicates the mass transfer from one region to another due to temperature gradients. ...
... 11 Furthermore, the present measured data of artificially triggered lightning provide reference data for further research on lightning and artificially triggered lightning. 13 2.39 Â 10 18 1.5-2 Uman (1964) 37 24 000 4.3 Â 10 18 Guo et al. (2009) 12 30 300 3.01 Â 10 18 2.26 Gorin and Inkov (1962) 38 20 000-40 000 ...
Based on plasma physics methods, the relationship among the channel current (i), core channel radius ( r c c), and other related parameters including electrical conductivity ( σ), thermal conductivity ( λ e), and thermal diffusion coefficient ( D e T) was investigated and strong interdependence was found among these parameters. Then, these dependent relationships together with the measured electron temperature ( T e) and electron density ( n e), derived from spectral diagnostics, were applied to determine the measured results on the i, r c c, σ, λ e, and D e T of channel plasma in artificially triggered lightning along with their measured accuracies. Good accordance can be found with the aid of comparisons with other measurements of the artificially triggered lightning [L. Cai et al., J. Electrost. 109, 103537 (2021)].
... For example, Herschel (1868), Slipher (1917), Orville (1975) studied the lightning emission spectra in the visible band, and Salanave (1961), Warner et al. (2011), Harley et al. (2021) extended the study of emission spectra to near infrared band. Cen et al. (2011), Dong et al. (2017), An et al. (2019), Liu et al. (2019b), An et al. (2021) studied physical characteristics along the lightning discharge path based on emission spectra of lightning. Weidman et al. (1989) recorded the lightning spectra in the near-infrared band of 850-1400 nm, and concluded that the average temperature of the lightning discharge path is approximately 16,000 K. Qu et al. (2012) studied the near-infrared spectra in the range of 760-970 nm and calculated that the temperature of the three lightning discharge paths are all about 16,000 K. Zhang et al. (2013) analyzed the radiation characteristics of lightning plasma in the visible and infrared bands, and calculated that the temperature of the lightning discharge path can reach more than 30,000 K. Mu et al. (2016) found that the temperature decay of the lightning discharge path is slower than the current change and that the temperature of the lightning discharge path remains at about 20,000 K up to 200-400 μs after the peak current by using the time-resolved spectra of the lightning return stroke process. ...
The paper presents a systematic description about the observation scheme analysis and practical observation of artificially triggered lightning with a ground-based microwave radiometer together with other discharging observation instruments at Guangzhou Field Experiment Site for Lightning research and testing in Conghua, Guangdong in the thunderstorm season of the 4 consecutive years from 2016 to 2019. The results from statistical analysis of the brightness temperature data observed from 2017 to 2019 show that: (1) The frequencies such as 28, 30, 51.25 and 51.76 GHz in atmospheric window are more likely to respond with outstanding brightness temperature pulses than other observation frequencies of the radiometer; (2) When the elevation angle is 30°, the observation distance is relatively short (99 m in this study), and the “lightning observation mode” is adopted, the efficiency for a ground-based microwave radiometer to capture the lightning heating effect caused by artificially triggered lightning can be improved; (3) The observation efficiency of the 3 years as a whole is 71.4% but gradually increases year by year; (4) The radiometer observation data can be used to reveal the characteristics of lightning heating effects such as duration and lightning current integral; (5) Combined with the lightning current data measured by a coaxial shunt during the experiment, it was found that the estimated lightning heating effect durations based on 25 artificially triggered lightning observations are well consistent with the lightning current durations, as shown by the correlation coefficient of 0.73. This also implies that the radiometer working on the lightning observation mode presented by this paper can observe the lightning heating effect and estimate its duration.
Atmospheric electricity is composed of a series of electric phenomena in the atmosphere. Significant advances in atmospheric electricity research conducted in China have been achieved in recent years. In this paper, the research progress on atmospheric electricity achieved in China during 2019–22 is reviewed focusing on the following aspects: (1) lightning detection and location techniques, (2) thunderstorm electricity, (3) lightning forecasting methods and techniques, (4) physical processes of lightning discharge, (5) high energy emissions and effects of thunderstorms on the upper atmosphere, and (6) the effect of aerosol on lightning.
Transition rates, collision excitation cross sections, and collision excitation rate coefficients of neutral N I atom and N II ions were calculated by Flexible Atomic Code that is based on the multiconfiguration Dirac-Fock method. The line intensity of some strong spectral lines were calculated. Then the dependent relationship among the ratio of line intensity I′I, the electron density ne and the electron temperature T were obtained. The calculation shows that the electron density has some dependence on the temperature and the ratio of line intensity. Furthermore, through applying the theoretical calculations to the channel plasma spectra of artificially triggered lightning, the electron densities were diagnosed at different channel locations and times. The accuracy of the electron density was estimated using the degree of accordance, which can pick out the diagnostic data that can best reflect the real state of plasma from a large number of statistical data.
In this paper, improved continuous wavelet transform is used to analyze the dispersion characteristics of a group of optical radiation signals of return stroke in an artificially triggered lightning, and the analysis results are compared with the results calculated by the classical R-L-C transmission line model. The analysis results show that the arrival time of different frequency components of the optical radiation of return stroke presents nonlinear variation with frequency. Moreover, a turning point always appears in the low frequency band on the arrival time curves of different frequency components, and the turning frequency is usually between 10 kHz and 25 kHz. The existence of this turning frequency provides a new kind of parameterization basis for evaluating the characteristic and conductivity of the return stroke channel. Based on this, the channel conductivities of the six return strokes of this triggered lightning are estimated. The average variation ranges from 0.59 × 10⁴ S/m to 0.96 × 10⁴ S/m, and the overall average value is about 0.77 × 10⁴ S/m, which are similar to the classical evaluation results.
Using the spectral data of a lightning continuing discharge process observed on the 600‐m‐high Canton Tower, experimental verification of the optical thickness of lightning neutral nitrogen (NI) and neutral oxygen (OI) radiation in the near‐infrared spectrum is presented first by comparing the measured relative intensities of two NI multiplets with theoretical values. For the first time, the spectral evolution characteristics of the tall structure lightning continuing discharge process show that visible band singly ionized lines were apparent for approximately 320–400 µs. The ionized lines with higher excitation energies and the neutral lines with lower excitation energies coexist for approximately 240–320 µs, which means that there is a hot region radiating ionized lines in a radial direction from the lightning channel, but at the same time there is also a cold region radiating neutral lines.
