NUV/Blue spectral observations of sprites in the 320-460 nm region: ${\mathrm N_2}$ (2PG) Emissions

TL;DR

This study used a NUV spectrograph on aircraft to observe sprites, confirming N2 (2PG) emissions dominate in the 320-460 nm range with a characteristic energy of about 1.8 eV, aligning with previous findings.

Contribution

First aircraft-based NUV spectroscopic observations of sprites in the 320-460 nm range confirming N2 (2PG) dominance and characteristic energy.

Findings

NUV/blue emissions are mainly N2 (2PG)

Negligible N2+ (1NG) presence confirmed

Characteristic energy of ~1.8 eV established

Abstract

A near-ultraviolet (NUV) spectrograph (320-460 nm) was flown on the EXL98 aircraft sprite observation campaign during July 1998. In this wavelength range video rate (60 fields/sec) spectrographic observations found the NUV/blue emissions to be predominantly N2 (2PG). The negligible level of N2+ (1NG) present in the spectrum is confirmed by observations of a co-aligned, narrowly filtered 427.8 nm imager and is in agreement with previous ground-based filtered photometer observations. The synthetic spectral fit to the observations indicates a characteristic energy of ~1.8 eV, in agreement with our other NUV observations.