N2+ Emission in Lightning

Abstract Comparison of slitless grating spectra with slit spectra, of lightning shows that the strength of the N2+ bands is distinctly different when observed by these two methods. The wide variations in lightning spectra reported by various observers may, therefore, have been influenced in some degree by the method of observation. Examination of seven possible modes of excitation of the N2+ bands leads us to suspect that the molecular emission recorded on slit spectra occurs at some distance from the visible lightning stroke, probably in terminal streamers inside the cloud. We also suggest that the occasional occurrence of N2+ in slitless spectra probably arises from the continuing current luminosity.