Correlation between the spectral features and electric field changes of multiple return strokes in negative cloud‐to‐ground lightning

Abstract

Using high time‐resolved spectra and simultaneous records of the electric field change of three negative cloud‐to‐ground (CG) lightning flashes with multiple return strokes, the correlations between the total intensity of ionic lines in the spectra and the corresponding amplitude of the initial electric field change, as well as between the total intensity of the spectra and the channel apparent diameter, have been analyzed. The analysis shows the following: (1) The amplitude of the initial electric field change is roughly proportional to the total intensity of ionic lines. (2) The total intensity of the spectra shows a significant linear correlation with the apparent diameter of the channel. (3) The total intensity of ionic lines for 17 analyzed return strokes decreases with increasing height along the channel, which is consistent with the current variation along the channel in the modified transmission line model; the Master, Uman, Lin, and Standler model; and the Diendorfer‐Uman model. Meanwhile, the total intensity of ionic lines for other two analyzed return strokes along the channel without attenuation, this is consistent with the current variation along the channel in the Bruce‐Golde model, the transmission line model, and the Traveling Current Source model.

Shockwave-assisted laser filament conductivity

“…In this natural process, an original lightning strike is followed by subsequent flashes propagating along the same path, that has moved as a whole with the air mass under the influence of wind. The delay between reilluminations ranges from tens to hundreds of milliseconds [36][37][38][39][40] strikes, comparable with the conductivity lifetime resulting from shockwave-assisted discharges in our experiments.…”

Evolution of Discharge Characteristics Along the Positive Cloud‐To‐Ground Lightning Channel

“…Both increase with the increase of channel height. The positive correlation between the total ionic-line intensity in the spectrum and discharge current is confirmed by Wang et al ( , 2017. Moreover, in the high-time-resolved optical observations at different heights of triggered-lightning channels, Carvalho et al (2015) have found that the peak impulse luminosity was roughly proportional to the peak current squared at the channel bottom.…”

Using Saha‐Boltzmann Plot to Diagnose Lightning Return Stroke Channel Temperature

“…To 250 μs, with the attenuation of the current, the intensity of all spectral lines is greatly reduced. As the ionic line strength is closely related to the discharge current (Wang et al, ; Wang et al, ), it rapidly decreases with the attenuation of the current, while the channel temperature depends on the action integral of the current. The temperature values hinge on the intensity ratio of lines with different excitation energy when it is diagnosed by equations and .…”

“…Consistent with the discharge characteristics of most negative flashes, the total intensity of the spectra of R0 is stronger than that of the subsequent return strokes. The lines from NII with high excitation energy are also strongest in the spectrum of R0, which means that its discharge current is the most intense (Wang et al, ; Wang et al, ).…”

“…The high time‐resolved spectra obtained by Walker and Christian () showed that NII, NI, and OI spectral lines were detected simultaneously in the initial and peak current stages of lightning stroke return. Since the ionic line is chiefly the contribution of the core current channel, and the atomic line is mainly from the peripheral channel (Orville, ; Wang et al, ; Wang et al, ), the temperature obtained by Saha‐Boltzmann plot method is not for core current channel.…”