The physical mechanism of nitric oxide formation in simulated lightning

• Published in: Geophysical research letters Vol. 28; no. 20; pp. 3867 - 3870
• Main Authors: Navarro‐González, Rafael, Villagrán‐Muniz, Mayo, Sobral, Hugo, Molina, Luisa T., Molina, Mario J.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 15.10.2001; American Geophysical Union
• Subjects: Chemical composition and interactions. Ionic interactions and processes; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; Shock heating; Laboratory study; Discharge channel; Production rate; Physical simulation; Nitric oxide; Lightning; Hot plasma; Experimental study; Formation mechanism
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2001GL013170

We report an experimental assessment of the contributions of the shockwave and the hot channel to the production of nitric oxide by simulated lightning. Lightning in the laboratory was simulated by a hot plasma generated with a pulsed Nd‐YAG laser. The temporal evolution of electric breakdown in air at atmospheric pressure was studied from the nanosecond to the millisecond time scale by shadowgraphy and interferometry techniques. The shockwave front velocity was determined to be about 60 km s−1 at 20 ns and the temperature behind the shock front was estimated to be about 105 K. The production yield of nitric oxide by shock heating is estimated to be: P(NO) (3±2) × 1014 molecule J−1. In contrast it was calculated that the production yield of NO by the hot channel is as much as P(NO)=(1.5±0.5) × 1017 molecule J−1. To the extent our simulation is an accurate representation of natural lightning, the hot channel is the dominant region for nitrogen fixation.