The Boltzmann Vibrational Temperature of N2 (B3Πg) Derived From ISUAL Imager Multiband Measurements of Transient Luminous Events

Abstract

AbstractOne of the main challenges for the observation of a transient luminous event (TLE) is to observe TLEs in different emission bands. Here, we show TLEs recorded using the ISUAL 427.8 nm, 630 nm, N2 1P (623–750 nm) and 762‐nm‐filtered imager, and we analyze the 630‐nm‐filtered, N2 1P‐filtered, and 762‐nm‐filtered images of TLEs for estimating the N2 (B3Πg) Boltzmann vibrational temperature in comparison with the theoretical N2 1P spectrum. For ISUAL recorded sprites, the average brightness of N2 1P (I1p), 762 nm (I762), and 630 nm (I630) emission was 2.3, 0.6, and 0.02 MR. The N2 (B3Πg) vibrational temperatures (Tv) was estimated to be 2800 K, 3200 K, and 4300 K for multiband emission ratios of I630/I1p, I630/I762, and I762/I1p. For observed elves, the average brightness I1p, I762, and I630 were 170, 50, and 3 kR. The estimated Tv values were 3700 K, 3700 K, and 3800 K for ratios I630/I1p, I630/I762, and I762/I1p. For observed gigantic jets, the derived Tv values were 3000–5000 K for a ratio I762/I1p. Through N2 (B3Πg) Tv analyses from emission ratios of ISUAL multiband observation, we derived the N2 (B3Πg) vibrational temperature that ranges between 3000 and 5000 K or higher in TLEs. Accuracy and variations of derived N2 (B3Πg) Tv are also discussed while relative population of vibrational levels in the Boltzmann equilibrium are also compared with past spectra observation.