Tingting An’s research while affiliated with Northwest University and other places

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Publications (24)

Energy level structure diagram of the N II ion and the corresponding spectral lines in table 2.
Original lightning channel of the first return stroke and its first-order diffraction spectrum.
Experimental and simulated spectra in the range of 400–650 nm. (a), Experimental spectra from figure 2. (b), The CRM simulation spectrum (Te = 23 000 K and ne = 1.0×10¹⁸cm⁻³) while the content of nitrogen and oxygen elements are 78% and 21%, respectively. (c), The broadened spectrum with a full width at half maximum (FWHM) of 1.5 nm. Enlarged view of the theoretical spectral lines of N II ion near 444.7 nm (d), 500.5 nm (e) and 568.0 nm (f). Note that both the experimental and theoretical intensities are normalized to A1.
Comparison between the experimental and calculated (Te = 23 000 K and ne = 1.0×10¹⁸cm⁻³) spectral profiles of N II ion. (a), The black lines are the experimental spectral profiles in the wavelength range of 498–503 nm and 565-570 nm which extracted from figure  3(a). The colored lines are the CRM calculated results using Gaussian distribution with the FWHM of 1.5 nm. (b), The theoretical profiles fitted by summation algorithm (purple). The shaded region express the total relative intensity of experimental spectral profiles.
The distribution of intensity-proportion of characteristic lines in the Te-ne space. (a), 500.52 nm in 500.5 nm multiple lines; (b), 567.96 nm in 568.0 nm multiple lines.

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Precise determination of lightning plasma parameters based on a collisional-radiative model
  • Article
  • Publisher preview available

January 2025

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10 Reads

Yingying An

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Xiaozhi Shen

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Feng Wei

A fine spectrum of natural lightning has been simulated by collisional-radiative model (CRM), and the line-intensities of N II dependent on electron temperature (Te) and electron density (ne) were obtained. It was found that the intensity proportion of 2p3d ³F 4∘ → 2p3p ³D3 and 2p3p ³D3 → 2p3s ³P 2∘ transitions in the multiple spectral lines to which they belong tend to stabilize in the Te-ne variation space, which is an inherent physical property that can be applied in determining the experimental intensity of characteristic lines from the total intensity of overlapped lines. By accurately matching the theoretical intensity-ratio with the experimental one, two intersections of contours of line-intensity ratios in the two-dimensional plane of Te-ne are derived, and then the Te and ne in the lightning channel were diagnosed simultaneously. The precise spectral analysis method and plasma diagnostic technique are the basis for researching other physical characteristics of lightning discharges, this work also has application value in artificially triggered lightning, laser-guided lightning, arc discharge, etc.

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Photographs of the original spectra of natural lightning recorded with a slitless spectrometer in the area of Qinghai Province, China. The left and right sides of the photo are the original lightning channel and its diffraction spectrum, respectively. White arrows ${a}$ a and ${b}$ b mark the relatively weak NII 444.7 nm and NII 463.0 nm, respectively. Marked on the lower right are some of the stronger spectral lines, where NII 500.5 represents the spectrum of the NII ion at a wavelength of 500.5 nm.
Lightning plasma spectra at wavelengths of 400–900 nm.
The determination of ${T_e}$ T e and ${n_e}$ n e using the ranges of fitting values ${k_{\rm{fit}}}$ k f i t and intercept ${b_{\rm{fit}}}$ b f i t . The ${k_{\rm fit1}} \lt {k_{\rm{fit}}} \lt {k_{\rm fit2}}$ k f i t 1 < k f i t < k f i t 2 denotes the range of fitting slope. ${{B}_1} - {{B}_8}$ B 1 − B 8 represents the spectral data arising from ${\rm N}\;{\rm I}:\;{746.8},\;{862.9}\;{\rm nm}$ N I : 746.8 , 862.9 n m and ${\rm N}\;{\rm II}:\;{444.7},\;{463.0},\;{568.0},\;{594.2}\;{\rm nm}$ N I I : 444.7 , 463.0 , 568.0 , 594.2 n m .
The changing tendency of fitting intercept ( $\xi$ ξ ) versus the abundance ( $\eta$ η ) for O I and N II together with the measured process of $\xi$ ξ . In (a), ${\xi _{\rm{O\;I}}}$ ξ O I $\ne$ ≠ ${\xi _{\rm{N\;II}}}$ ξ N I I represents different abundances in O I and N II. In (b), the discrepancy of ${\eta _{\rm{O\;I}}}$ η O I and ${\eta _{\rm{N\;II}}}$ η N I I ascribes the difference in partition function ${U_s}$ U s . ${\xi _{\rm{O\;I}}} = - 1.74$ ξ O I = − 1.74 and ${\xi _{\rm{N\;II}}} = 0.71$ ξ N I I = 0.71 in (a) can be used to determine the ${\eta _{\rm{O\;I}}}$ η O I and ${\eta _{\rm{N\;II}}}$ η N I I in (b) by 6.29% and 61.26%. A limiting case exists in $\eta \approx$ η ≈ 0%.
The abundances of N I, N II, N III, O I, O II, and O III with the CF-LIBS method for multiplet along with their total nitrogen and oxygen abundances. Saha-extrapolation represents that based on the measured $\eta$ η -values of N II and O I, other abundances can be extrapolated using the Saha expression. The ${T_e}$ T e and ${n_e}$ n e , separately, adopt 23,700 K and $4.8 \times \;{10^{18}}\;{{\rm cm}^{- 3}}$ 4.8 × 10 18 c m − 3 . ${\eta _{\rm N}}$ η N and ${\eta _{\rm O}}$ η O denote the total abundance of nitrogen and oxygen.

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Abundance determination of atoms and ions in the channel plasma of lightning

August 2024

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19 Reads

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1 Citation

Feng Wei

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Xiaozhi Shen

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Mengle Su

Based on the multi-configuration Dirac-Fock (MCDF) method, accurate atomic spectral data were calculated and used for plasma spectral diagnostics and line identification. The formation of multiplet emission lines due to the proximity of the upper and lower levels of the transition is common. For multiplet analysis, some software is often used for line separation; however, this is a rather inaccurate process. In this study, the CF-LIBS and Saha-Boltzmann methods for multiplet emission lines are derived, which allow the use of multiplet and singlet emission lines. This CF-LIBS and Saha-Boltzmann method for multiplet is used in lightning plasma spectroscopy for obtaining particle abundances in the lightning channel. It was found that there is a dependence between the intercept, ξ\xi ξ , of the Boltzmann plot and the ionic abundance, η\eta η , of the plasma, and that the differences in η\eta η in different particles are attributed to the varying amounts of nitrogen and oxygen in the air. Then, the final measured η\eta η -data indicate that N II ions are the most abundant in this lightning, with N III and O III ions being extremely rare. The presently reported data are in better agreement with some verification data and other measurements.

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Original spectrum of each return stroke and fast and slow electric field change waveform caused by the lightning. (a) Lightning return stroke spectra. (b) Slow electric field change waveform. (c) Fast electric field change waveform.
Amplified waveform of the fast and slow electric field changes for the (a) first return stroke, R0, and (b) the subsequent return stroke, R1.
Optical picture of the upward branch from the main channel node in the initial stage of the first return stroke.
Change in the temperature and electron density with height in the initial stage of the first return stroke. The pink line indicates the main channel and the light cyan line indicates branch channel b1 near the bottom of the cloud. (a) The change in temperature with height in the initial stage of the first return stroke. (b) The change in electron density with height in the initial stage of the first return stroke.
Channel development of DSL1, DL2, DL3, DL4, DSL5, DSL6, and DSL7 before return stroke R1–R7. DSL is the dart‐stepped leader and DL is the dart leader.

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Spectral Study of Rare Upward Developing, Circling, and Branching Cloud‐To‐Ground Lightning

May 2024

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87 Reads

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1 Citation

Liwen Xu

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Xueqiang Gou

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Hong Deng

The development of cloud‐to‐ground (CG) lightning channel is one of the main bases reflecting the discharge characteristics. Time‐resolved spectra of CG lightning with eight return strokes were recorded by a slit‐less high‐speed spectroscope. We found an unusual phenomenon in which a branch developed upward from a node following a circling structure into the cloud after the first return stroke. To investigate the propagation properties of this lightning, characteristic parameters such as the two‐dimensional speed of the leader, node temperature, and electron density are analyzed. The physical mechanism of the branch is discussed. Spectral analysis reveals that the main channel temperature and electron density are approximately 2.72–3.07 × 10⁴ K and 0.23–2.03 × 10¹⁸ cm⁻³, respectively. The temperature and electron density increase as the branch approaches the cloud base, similar to the feature of the main channel approaching the ground. The temperature and electron density of the node are higher than at other locations in the circular channel, indicating that massive charge accumulated around the node. Lightning occurred in the Qilian Mountains in a complex landscape, which easily yielded an uneven distribution in the local electric field of the air, resulting in channel bending, kinking, and even circle development. The phenomenon of the branch developed from the node to the cloud may be due to the fact that the branch is formed during the return stroke process.

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Citations (13)

... The channel plasma of lightning was based on two basic assumptions: 15,16 (a) The lightning channel is optically thin; and (b) the channel is in local thermodynamic equilibrium (LTE). Under the LTE assumption, the electron temperature (T e ) of a channel can be given by 17,18 ln ...

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Current, core channel radius, and related parameters of channel plasma in artificially triggered lightning
Temperature of apparent natural ball lightning obtained by examination of the spectra
  • Citing Article

  • November 2022

Tingting An

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... Lightning is a strong discharge phenomenon in the atmosphere. It is often accompanied by strong light, electromagnetic radiation, high temperature, strong currents, etc., which will cause lightning disasters [1][2][3][4][5]. The strong discharge current causes the peak temperature of the lightning to reach tens of thousands of degrees. ...

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Abundance determination of atoms and ions in the channel plasma of lightning
Time-evolution characteristics of spectrum and temperature of lightning discharge plasma
Hong Deng

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Tingting An

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Xueqiang Gou

... This paper studies negative lightning. Based on reference [22], Q t is set to − 10C. According to Gauss's theorem, when the total charge increases, the potential on a specific closed surface (with a fixed shape and position) is proportional to the amount of charge enclosed within it. ...

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The charge distribution in lightning downward leader channel based on RC distributed circuit model
The influence of leader charge on current intensity and spectral characteristics of return strokes
  • Citing Article

  • August 2022

Atmospheric Research

Linhui Chen

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Tingting An

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Facai Su

... An et al. (2019) reported that the total intensity ratio of the spectra to ionic lines is roughly equal to the diameter ratio of the outer corona envelope to the current-carrying channel core. If the outer corona envelope radius is assumed to be 6 cm (Tausanovic et al., 2017), then the mean channel core radii at the lower end of this tall structure lightning channel at 0.16 and 0.24 ms are estimated as 0.82 and 0.83 cm, respectively, which are consistent with the magnitude of the channel core radius reported in the literature Jayakumar et al., 2006;Wang et al., 2022). ...

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First Experimental Verification of Opacity for the Lightning Near‐Infrared Spectrum
The initial radius of lightning return stroke channel and its relation with discharge intensity
  • Citing Article

  • March 2022

Atmospheric Research

Wangsheng Wang

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Xin Huang

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Hong Deng

... Then, many works aimed to improve the time resolution of the spectrum in order to know the physical parameters' evolution inside the lightning channel. [13][14][15][16][17] In the laboratory, the spectrum of air plasma induced by a laser has something in common with the spectrum of lightning. Because the laser-induced air plasma and lightning are both generated in air at atmospheric pressure, they are pulsed. ...

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A spectral comparison of lightning discharge plasma and laser-induced air plasma
Conduction characteristics of lightning dart leader channel and its influence on the corresponding return stroke discharge intensity
  • Citing Article

  • December 2021

Xin Huang

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Ruibin Wan

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Wangsheng Wang

... Yang et al. [34] analyzed a single sprite produced using a mesoscale convective system (MCS). In addition, the spectra of the lightning were observed [35,36], and its physical parameters, such as the electron temperature, density, and conductivity in the channel, were quantitatively calculated, thus allowing the microphysical information inside and around the channel to be obtained. ...

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A Lightning Optical Automatic Detection Method Based on a Deep Neural Network
Effects of Atmospheric Attenuation on the Lightning Spectrum
Ruibin Wan

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Tingting An

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Hong Deng

... 1,2 Normally, the current thermal effect causes a high electron temperature of 20 000-30 000 K, which is the main source of human and animal casualties, forest fires, and electrical system damage. 3,4 The accompanying electromagnetic radiation has a strong burning impact on electronic devices. 5 Many physical parameters in a plasma channel, such as electron temperature (T e ), electron density (n e ), etc., can directly reflect the discharge characteristics of the lightning. ...

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Collisional-radiative modeling of the 2p3 l ( l = p,d) spectra of N II and application to lightning
Conductivity characteristics and corona sheath radius of lightning return stroke channel
  • Citing Article

  • August 2021

Atmospheric Research

Tingting An

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Ping Yuan

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Ruibin Wan

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... 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. ...

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Current, core channel radius, and related parameters of channel plasma in artificially triggered lightning
Evolution of Discharge Characteristics Along the Positive Cloud‐To‐Ground Lightning Channel
Tingting An

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Rongrong Chen

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Guorong Liu

... Most of the strong lines in the lightning channel plasma arise from the N II decays 2p3s-2p3p and 2p3p-2p3d. 4,40 Accurate calculation of their energy levels and transition rates is slightly influenced by the correlation effects of the inner-shell electrons 1s 2 . The present configurations involve {2pnl (n=2-6, l=s,p,d,f,g,h); 2s2p 3 ; 2p 4 ; 2s2p 2 ( 4 P)3l (l=s,p,d)}. ...

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Collisional-radiative modeling of the 2p3 l ( l = p,d) spectra of N II and application to lightning
The variation characteristics of lightning plasma conductivity along the discharge channel
  • Citing Article

  • August 2020

Xiaopeng Zhang

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Tingting An

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Ruibin Wan

... Spectral observations can record the emission spectrum of the lightning channel and can be used to retrieve physical information from inside the channel. Lightning spectral measurements with high spatial and temporal resolution have been used to reveal the details of lightning channels (Zhang et al., , 2020bWang et al., 2019cWang et al., , 2021dWang et al., , 2022bLiu et al., 2019aLiu et al., , b, 2021dLiu et al., , 2022Wan et al., 2021;Chen et al., 2022b). Zhang et al. (2019a) investigated the variation characteristics of return stroke current along the discharge channel, and three types of variation trends with height were found. ...

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A Review of Atmospheric Electricity Research in China from 2019 to 2022
A visible channel core and the channel structure below the connection point for natural cloud-to-ground lightning
  • Citing Article

  • August 2019

Guorong Liu

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Tingting An

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