High-Speed Ultraviolet and Visible Optical Emission Spectroscopy of High-Voltage Impulses Representing Lightning

To better understand lightning interactions with the atmosphere, a high-speed (streak) spectrograph was used to characterise various high voltage impulses representing lightning. A Marx generator was used to produce 1.2/50 μs high voltage impulses, according to the IEC 60060 standard, ranging from 60 kV to 160 kV. The atomic emission spectrum was captured using a high-speed streak system at resolutions of 0.35 μs/pixel to 0.14 μs/pixel. Spectral data were first recorded over a broad range of 250 to 990 nm, covering a part of the ultraviolet spectrum, full visible spectrum and into near-infrared. Then three smaller bands were chosen for high resolution spectral data to enable the identification of key atomic emission lines such as Oxygen-I, Nitrogen-I and II, and Argon-I from the atmosphere, as well as Tungsten-I from the experiment electrodes. It was observed that an increase in high voltage lead to greater spectral intensity with more prominent lines, as expected, indicating an increase in energy transfer into the surrounding atmosphere. Subsequent analysis of the data resulted in both temperature and energy measurements of these arcs. Such spectral signatures have important implications for refining atmospheric electricity models and better understanding risks associated with lightning, particularly for built infrastructure, such as struck power lines and wind turbines, but also natural features, like forests and woodland. It is the intention that this work will progress onto the study of spectra from laboratory generated lightning arcs.