资源环境科技发展态势分析平台

In the mid 1960s, researchers laid the foundation for modern quantitative lightning spectroscopy. They were the first to acquire time-resolved return stroke spectra and the first to use spectroscopy as a diagnostic technique to characterize the physical properties of the lightning channel (Orville, 1968a, https://doi.org/10.1175/1520-0469(1968)025<0827:AHSTRS>2.0.CO;2, 1968b, https://doi.org/10.1175/1520-0469(1968)025<0839:AHSTRS>2.0.CO;2, 1968c, https://doi.org/10.1175/1520-0469(1968)025<0852:AHSTRS>2.0.CO;2; Salanave, 1961, https://doi.org/10.1126/science.134.3488.1395; Uman, 1966, https://doi.org/10.1109/MSPEC.1966.5217654). Now, almost 50 years later, technology, including high-speed cameras, volume-phase holographic gratings, and triggered lightning, has progressed to the point at which new studies in lightning spectroscopy are needed to verify and improve upon past measurements. In this study triggered lightning spectra were recorded at 673 kfps (1.5 mu s per frame) with an exposure time of 1.1 mu s. Temperature, number density, and pressure on a 1.5-mu s time scale are presented here for a five-stroke-triggered lightning flash. The analysis yields temperatures of the return stroke of greater than 40,000 K as well as electron number densities greater than 10(19) cm(-3) and peak pressures from 20-350 atm, significantly greater than previous studies. The analysis reveals that in the initial microseconds of the return stroke, the physical characteristics within the channel are rapidly changing and that submicrosecond resolution is needed to observe the initial ionized channel in greater detail.