Spectrum of the lightning stepped leader

A high-speed camera has been modified to a slitless spectrograph to record the spectral emissions from a section of the lightning channel. Spectral emissions from a 2-meter section of a negatively charged stepped-leader channel are recorded. The downward progression of the leader caused the isolated vertical section to radiate seven discrete times before the upward-moving return stroke produced an overexposed time-resolved spectrum. The discrete spectral emissions were recorded at intervals of 31–42 μsec. Stepped-leader spectral emissions in the 5600- to 6600-A regions are characterized by singly ionized nitrogen (N II) emissions at 5680 and 5942 A, and Hα emissions at 6563 A. These leader channel emissions vary as a function of time as the stepped leader progresses toward the ground. A temperature of 30,000°K is calculated for the leader step. The diameter of the leader channel defined by the N II spectral emissions is less than 0.5 meter.

[1]  B. Schonland,et al.  Progressive lightning. VII Directly-correlated photographic and electrical studies of lightning from near thunderstorms , 1947, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[2]  R. Orville.  High-Speed, Time-Resolved Spectrum of a Lightning Stroke , 1966, Science.

[3]  Richard Edmonds Orville,et al.  A spectral study of lightning strokes , 1966 .

[4]  Basil Ferdinand Jamieson Schonland,et al.  Progressive lightning IV-The discharge mechanism , 1938 .

[5]  L. Loeb.  The mechanisms of stepped and dart leaders in cloud-to-ground lightning strokes , 1966 .

[6]  M. Uman,et al.  The Density, Pressure, and Particle Distribution in a Lightning Stroke near Peak Temperature , 1964 .

[7]  C. E. R. BRUCE,et al.  The Lightning and Spark Discharges , 1941, Nature.

[8]  L. Salanave.  The Optical Spectrum of Lightning , 1964 .

[9]  K. Berger,et al.  Novel observations on lightning discharges: Results of research on Mount San Salvatore , 1967 .

[10]  G. A. Dawson,et al.  Discussion of paper by E. L. Hill and J. D. Robb, ‘Pressure Pulse from a Lightning Stroke’ , 1968 .

[11]  M. Uman.  Quantitative lightning spectroscopy , 1966, IEEE Spectrum.

[12]  B. Schonland,et al.  The Lightning Discharge , 1956 .

[13]  R. Orville.  THE COLOUR SPECTRUM OF LIGHTNING , 1966 .

[14]  Basil Ferdinand Jamieson Schonland,et al.  The pilot streamer in lightning and the long spark , 1953, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[15]  M. Prueitt.  The excitation temperature of lightning , 1963 .

[16]  L. Salanave.  The Optical Spectrum of Lightning: A revival of the spectrographic study of lightning may help solve some outstanding puzzles in could physics. , 1961, Science.

[17]  M. Uman,et al.  The opacity of lightning , 1965 .

[18]  C. Bruce,et al.  The initiation of long electrical discharges , 1944, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[19]  H. Maecker.  Der elektrische Lichtbogen , 1951 .