High Spectral Resolution Spectroscopy of Sprites: A Natural Probe of the Mesosphere

Abstract

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. ©2018. American Geophysical Union. All Rights Reserved. ; This work was supported by the Spanish Ministry of Science and Innovation, MINECO, under projects FIS2014-61774-EXP, ESP2015-69909-C5-2-R, and ESP2017-86263-C4-4-R, and by the EU through the FEDER program. The contribution of O. V. and J. M. was supported by projects ESP2013-48032-C5-3-R and ESP2015-69909-C5-5-R. A. L. was supported by the European Research Council (ERC) under the European Union H2020 program/ERC grant agreement 681257. We acknowledge NowCast for providing LINET lightning data for research purposes. We also acknowledge AEMET (Spanish Meteorological Service) for providing some lightning data corresponding to January 2017. ; Peer reviewed