The Boltzmann Vibrational Temperature of N₂ (B³Π_g) Derived From ISUAL Imager Multiband Measurements of Transient Luminous Events

Abstract

One of the main challenges for the observation of a transient luminous event (TLE) is toobserve 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 Π 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 Π 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 Π g ) T v analyses from emission ratios of ISUAL multiband observation, we derived the N 2 (B 3 Π g ) vibrational temperature that ranges between 3000 and 5000 K or higher in TLEs. Accuracy and variations of derived N 2 (B 3 Π g ) T v are also discussed while relative population of vibrational levels in the Boltzmann equilibrium are also compared with past spectra observation.

Chemical Activity of Low Altitude (50 km) Sprite Streamers

“…Optical diagnostic methods of sprites are used to estimate the plasma characteristics of sprites (Kuo et al., 2019; Malagón‐Romero et al., 2019; Pérez‐Invernón, Luque, Gordillo‐Vazquez, et al., 2018) including the possibility that they could (or not) locally heat up the surrounding atmosphere (Gordillo‐Vázquez et al., 2018; Parra‐Rojas, Passas, et al., 2013; Pasko et al., 1998). In turn, chemical and electrodynamical models of sprites indicate that they can produce nitrogen oxides (NO x = NO + NO 2 ) (Enell et al., 2008; Evtushenko et al., 2013; Gordillo‐Vázquez, 2008, 2010; Gordillo‐Vázquez et al., 2012; Hiraki et al., 2008; Luque & Gordillo‐Vázquez, 2011a; Sentman et al., 2008; Winkler & Nothold, 2014), nitrous oxide (N 2 O) (Parra‐Rojas et al., 2015; Pérez‐Invernón et al., 2020) and hydrogen oxide radicals (HO x = H + OH + HO 2 ) (Winkler et al., 2021; Yamada et al., 2020) in the mesosphere and the lower‐ionosphere possibly playing a role in the upper atmospheric budget of ozone.…”