Submicrosecond (0.476 μs per frame with an exposure time of 160 ns) high‐resolution (0.38 nm) time‐resolved spectra of laboratory‐produced lightning‐like electrical discharges have been recorded for the first time within the visible spectral range (645–665 nm). The spectra were recorded with the GrAnada LIghtning Ultrafast Spectrograph (GALIUS), a high‐speed imaging spectrograph recently developed for lightning research in the IAA‐CSIC. Unprecedented spectral time dynamics are explored for meter long laboratory electrical discharges produced with a 2.0 MV Marx generator. The maximum electron density and gas temperature measured in a timescale of ≤0.50 μs (160 ns) were, respectively, ≃1018 cm−3 and ≃32,000 K. Overpressure in the lightning‐like plasma channel, black‐body dynamics, and self‐absorption in spectral lines were investigated.

We present the first high spectral resolution (0.24 nm) spectra of sprites. These spectra were recorded in Europe in the summers and falls of 2015 and 2016 and during January 2017. The use of high spectral resolution has allowed us to resolve for the first time the internal (vibrorotational) structure of the sprite molecular N2 first positive system and to quantify the local gas (rotational) temperature of the mesosphere under the influence of sprites revealing that there is no measurable heating of the atmosphere associated to sprites at the altitudes explored. The temperatures of the explored region of the mesosphere range between 149 K ± 10 K and 226 K ± 20 K. The recorded spectroscopic data also provide valuable quantitative information on the concentrations of some of the vibrational levels of molecular nitrogen involved in transient red‐near‐infrared optical emissions from sprites. The regions of the transient luminous events recorded with our spectrograph (equipped with a horizontally oriented slit) correspond to altitudes in the 66 km to 74 km ± 5 km range.

[1] We have studied laboratory low pressure (0.1 mbar Ä p Ä 2 mbar) glow air discharges by optical emission spectroscopy to discuss several spectroscopic techniques that could be implemented by field spectrographs, depending on the available spectral resolution, to experimentally quantify the gas temperature associated to transient luminous events (TLEs) occurring at different altitudes including blue jets, giant blue jets, and sprites. Laboratory air plasmas have been analyzed from the near UV (300 nm) to the near IR (1060 nm) with high (up to 0.01 nm) and low (2 nm) spectral resolution commercial grating spectrographs and by an in-house intensified CCD grating spectrograph that we have recently developed for TLE spectral diagnostic surveys with ' 0.45 nm spectral resolution. We discuss the results of lab tests and comment on the convenience of using one or another technique for rotational (gas) temperature determination depending on the altitude and available spectral resolution. Moreover, we compare available low resolution (3 nm Ä Ä 7 nm) N 2 1PG field recorded sprite spectra at 53 km (' 1 mbar), and resulting vibrational distribution function, with 1 mbar laboratory glow discharge spectrum ( = 2 nm) and synthetic sprite spectra from models. We found that while the relative population of N 2 (B 3 … g , v = 2 -7) in sprites and laboratory produced air glow plasmas are similar, the N 2 (B 3 … g , v = 1) vibrational level in sprites is more efficiently populated (in agreement with model predictions) than in laboratory air glow plasmas at similar pressures.Citation: Parra-Rojas, F. C., M. Passas, E. Carrasco, A. Luque, I. Tanarro, M. Simek, and F. J. Gordillo-Vázquez (2013), Spectroscopic diagnostics of laboratory air plasmas as a benchmark for spectral rotational (gas) temperature determination in TLEs,

We present the main parameters, design features, and optical characterization of the Granada Sprite Spectrograph and Polarimeter (GRASSP), a ground-based spectrographic system intended for the analysis of the spectroscopic signature of transient luminous events (TLEs) occurring in the mesosphere of the Earth. It has been designed to measure the spectra of the light emitted from TLEs with a mean spectral resolution of 0.235 nm and 0.07 nm/px dispersion in the wavelength range between 700 and 800 nm.

High speed spectra (between ∼380 nm and ∼800 nm) of meter‐long lightning‐like discharges recorded at 672,000 fps and 1,400,000 fps (with 1.488 and 0.714 μs time resolutions and 160 ns exposure time) show optical emissions of neutral hydrogen, singly ionized nitrogen, oxygen, and doubly ionized nitrogen which are similar to those found in natural lightning optical emissions. The spectra recorded in the near ultraviolet‐blue range (380–450 nm) and visible‐near infrared (475–793 nm) exhibited features of optical emissions corresponding to several molecular species (and emission bands) like cyanide radical (CN) (Violet bands), N2 (Second Positive System), N2+ (first negative system), C2 (Swan band) and CO (Quintet and Ångström bands). Molecular species can be formed at regions of the lightning‐like channel where the gas temperature would be milder and/or in the corona sheath surrounding the heated channel. We have quantified and compared electron densities and temperatures derived from different sets of neutral and ion line emissions and have found different sensitivities depending on the lines used. Temperatures derived from ion emissions are higher and change faster than those derived from neutral emissions.