Modeling the chemical impact and the optical emissions produced by lightning-induced electromagnetic fields in the upper atmosphere: the case of halos and elves triggered by different lightning discharges

Halos and elves are Transient Luminous Events (TLEs) produced in the lower ionosphere as a consequence of lightning-driven electromagnetic fields. These events can influence the upper-atmospheric chemistry and produce optical emissions. We have developed different two-dimensional self-consistent models that couple electrodynamical equations with a chemical scheme to simulate halos and elves produced by vertical cloud-to-ground (CG) lightning discharges, Compact Intra-cloud Discharges (CIDs) and Energetic In-cloud Pulses (EIPs). The optical emissions from radiative relaxation of excited states of molecular and atomic nitrogen and oxygen have been calculated. We have upgraded previous local models of halos and elves to calculate for the first time the vibrationally detailed optical spectra of elves triggered by CIDs and EIPs. According to our results, the optical spectra of elves do not depend on the type of parent lightning discharge. Finally, we have quantified the local chemical impact in the upper atmosphere of single halos and elves. In the case of the halo, we follow the cascade of chemical reactions triggered by the lightning-produced electric field during a long-time simulation of up to one second. We obtain a production rate of NO molecules by single halos and elves of 10$^{16}$ and 10$^{14}$ molecules/J, respectively. The results of these local models have been used to estimate the global production of NO by halos and elves in the upper atmopshere at $\sim10^{-7}$ Tg~N/y. This global chemical impact of halos and elves is seven orders of magnitude below the production of NO in the troposphere by lightning discharges

死に続ける女・葵上 -その機能的側面からのアプロ－チ-

7 pages, 5 figures, 2 tables.-- Printed version published May 11, 2006.The chemical composition of a low pressure hydrogen DC plasma produced in a hollow cathode discharge has been measured and modelled. The concentrations of H atoms and of H+, H2+ and H3+ ions were determined with a combination of optical spectroscopic and mass spectrometric techniques, over the range of pressures (p∼0.008-0.2 mbar) investigated. The results were rationalized with the help of a zero-order kinetic model. A comparatively high fraction (∼0.1 ± 0.05) of H atoms, indicative of a relatively small wall recombination, was observed. Low ionization degrees (< 10-4) were obtained in all cases. In general, the ionic composition of the plasma was found to be dominated by H3+, except at the lowest pressures, where H2+ was the major ion. The key physicochemical processes determining the plasma composition were identified from the comparison of experimental and model results, and are discussed in the paper.The SEUID of Spain (Projects FTN2003-08228-C03-03, FIS2004-00456) and the CSIC-CAM (Project 200550M016) are gratefully acknowledged for financial support.Peer reviewe

Size-selective breaking of the core-shell structure of gallium nanoparticles

This Accepted Manuscript is available for reuse under a CC BY-NC-ND 3.0 licence after the 12 month embargo period provided that all the terms of the licence are adhered toCore-shell gallium nanoparticles (Ga NPs) have recently been proposed as an ultraviolet plasmonic material for different applications but only at room temperature. Here, the thermal stability as a function of the size of the NPs is reported over a wide range of temperatures. We analyze the chemical and structural properties of the oxide shell by x-ray photoelectron spectroscopy and atomic force microscopy. We demonstrate the inverse dependence of the shell breaking temperature with the size of the NPs. Spectroscopic ellipsometry is used for tracking the rupture and its mechanism is systematically investigated by scanning electron microscopy, grazing incidence x-ray diffraction and cathodoluminescence. Taking advantage of the thermal stability of the NPs, we perform complete oxidations that lead to homogenous gallium oxide NPs. Thus, this study set the physical limits of Ga NPs to last at high temperatures, and opens up the possibility to achieve totally oxidized NPs while keeping their sphericityThe research is supported by the MINECO (CTQ2014-53334-C2-2-R, CTQ2017-84309-C2-2-R, MAT2016-80394-R, MAT 2015-65274-R/FEDER and MAT2017-85089-C2-1-R) and Comunidad de Madrid (NANOAVANSENS ref. S2013/MIT-3029) projects. ARC acknowledges Ramón y Cajal program (under contract number RYC-2015-18047). FN acknowledges support from Marie Sklodowska-Curie grant agreement No. 641899 from the European Union´s Horizon 2020 research and innovation programm

On the electrostatic field created at ground level by a halo

We investigate the effect of halo activity on the electrostatic field measured at ground level. We use electrostatic arguments as well as self-consistent simulations to show that, due to the screening charge in the ionosphere, the distant electrostatic field created by the uncompensated charge in a thundercloud decays exponentially rather than as the third power of the distance. Furthermore, significative ionization around the lower edge of the ionosphere slightly reduces the electrostatic field at ground level. We conclude that halos do not extend the range of detectability of lightning-induced electrostatic fields.This work was supported by the Spanish Ministry of Science and Innovation, MINECO under projects ESP2013-48032-C5-5-R, FIS2014-61774-EXP, and ESP2015-69909-C5-2-R and by the EU through the FEDER program. F.J.P.I. acknowledges a MINECO predoctoral contract, code BES-2014-069567. A.L. acknowledges support by a Ramon y Cajal contract, code RYC-2011-07801Peer reviewe

Global Frequency and Geographical Distribution of Nighttime Streamer Corona Discharges (BLUEs) in Thunderclouds

Blue LUminous Events (BLUEs) are transient corona discharges occurring in thunderclouds and characterized by strong 337.0 nm light flashes with absent (or weak) 777.4 nm component. We present the first nighttime climatology of BLUEs as detected by the Modular Multispectral Imaging Array of the Atmosphere-Space Interaction Monitor showing their worldwide geographical and seasonal distribution. A total (land and ocean) of E~11 BLUEs occur around the globe every second at local midnight and the average BLUE land/sea ratio is E~7:4. The northwest region of Colombia shows an annual nighttime peak. Globally, BLUEs are maximized during the boreal summer-autumn, contrary to lightning which is maximed in the boreal summer. The geographical distribution of nighttime BLUEs shows three main regions in, by order of importance, the Americas, Europe/Africa and Asia/AustraliapublishedVersio

Submicrosecond Spectroscopy of Lightning-Like Discharges: Exploring New Time Regimes

Abstract 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