The Boltzmann Vibrational Temperature of N_2 (B~3Π_g) Derived From ISUAL Imager Multiband Measurements of Transient Luminous Events

摘要

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~3Π_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~3Π_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~3Π_g) T_v analyses from emission ratios of ISUAL multiband observation, we derived the N_2 (B~3Π_g) vibrational temperature that ranges between 3000 and 5000 K or higher in TLEs. Accuracy and variations of derived N_2 (B~3Π_g) T_v are also discussed while relative population of vibrational levels in the Boltzmann equilibrium are also compared with past spectra observation.