Ultraviolet spectrum of the aurora (2000–2800 Å)

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Abstract
Ultraviolet spectra between 2000 and 2800 Å of an IBC II+ aurora were obtained by a rocket‐borne Ebert‐Fastie monochromator at 15‐Å resolution over Fort Churchill, Manitoba. The υ′=0–8 progressions of the N2 Vegard‐Kaplan system, the Δυ=8 sequence of the Lyman‐Birge‐Hopfield system, and a progression attributed to the Herman‐Kaplan system were identified by a synthetic spectrum analysis. Relative populations of the first eight vibrational levels of the A³Σu+ state at high altitude were obtained from the theoretically generated spectra, and quenching rate coefficients were derived for these eight levels by using an atomic oxygen concentration derived from data from another experiment on board. For υ=0 the quenching rate coefficient was found to be 2.0 × 10−10 cm³ s−1 and was not found to increase for higher vibrational levels. The intensity of the (0, 2) band of the Herman‐Kaplan (E³Σg+ → A³Σu+) system was found to be ∼5 times the theoretically predicted value, but even so, the cascade from E³Σg+ provides less than 2% of the A³Σu+ state population.