Spectroscopic diagnostics of laboratory air plasmas as a benchmark for spectral rotational (gas) temperature determination in TLEs

We have studied laboratory low pressure (0.1 mbar ≤ p ≤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 ≤Δ λ ≤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 (Δ λ =2 nm) and synthetic sprite spectra from models. We found that while the relative population of N 2 ( B 3 Π g , v =2−7) in sprites and laboratory produced air glow plasmas are similar, the N 2 ( B 3 Π 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.