The Boltzmann Vibrational Temperature of N-2 (B-3 Pi(g)) Derived From ISUAL Imager Multiband Measurements of Transient Luminous Events

One 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, N-2 1P (623-750 nm) and 762-nm-filtered imager, and we analyze the 630-nm-filtered, N-2 1P-filtered, and 762-nm-filtered images of TLEs for estimating the N-2 (B-3 Pi(g)) Boltzmann vibrational temperature in comparison with the theoretical N-2 1P spectrum. For ISUAL recorded sprites, the average brightness of N-2 1P (I-1p), 762 nm (I-762), and 630 nm (I-630) emission was 2.3, 0.6, and 0.02 MR. The N-2, (B-3 Pi(g)) vibrational temperatures (T-v) was estimated to be 2800 K, 3200 K, and 4300 K for multiband emission ratios of I-630/I-1p, I-630/I-762, and I-762/I-1p. For observed elves, the average brightness I-1p, I-762, and I-630 were 170, 50, and 3 kR. The estimated T-v, values were 3700 K, 3700 K, and 3800 K for ratios I-630/I-1p, I-630/I-762, and I-762/I-1p. For observed gigantic jets, the derived T-v values were 3000-5000 K for a ratio I-762/I-1p. Through N-2 (B-3 Pi(g)) T-v analyses from emission ratios of ISUAL multiband observation, we derived the N-2 (B-3 Pi(g)) vibrational temperature that ranges between 3000 and 5000 K or higher in TLEs. Accuracy and variations of derived N-2 (B-3 Pi(g)) T-v are also discussed while relative population of vibrational levels in the Boltzmann equilibrium are also compared with past spectra observation.