Transient Luminous Events Research Articles

A Framework for Efficient Calculation of Photoionization and Photodetachment Rates With Application to the Lower Ionosphere

AbstractA framework is developed to model photoionization of metals deposited in the lower ionosphere as a result of meteoric ablation and photodetachment of electrons from negative ions of the Earth's ionosphere due to sources of emission other than solar radiation. A wide range of the electromagnetic spectrum including cases of negligible, moderate, and significant absorption of radiation is considered. We limit our scope to the radiation transport through lower ionospheric regions, in case when molecular oxygen, O2, is considered as the main absorber of radiation as photoabsorption due to ozone is only effective at stratospheric altitudes and molecular nitrogen, N2, is transparent to radiation with wavelengths longer than ∼100 nm. We model photon transport in an exponential atmosphere and derive efficient differential representations of the problem in case of negligible photoabsorption and constant pressure approximations. Photoabsorption asymmetry in the atmosphere is demonstrated in case of photons with absorption scales comparable to the scale height of the atmosphere. The application of the model to photoionization in the lower ionosphere is demonstrated by considering photoionization of meteoric species due to photons of the Lyman‐Birge‐Hopfield (LBH) band system of N2 observed in the aurora and in the lightning‐induced transient luminous events. Furthermore, we model detachment of electrons from negative ions of the ionosphere due to the first positive and the second positive band systems of N2, and the first negative band system of N , also observed in the sources mentioned above.

Laboratory Simulation of the Effect of Volcanic Material on the Formation of Transient Phenomena Near the Boundary between the Middle and Lower Atmosphere

It is ascertained that heating of volcanic material from the Etna volcano (Italy) by an apokampic discharge reduces the voltage at which a positive streamer (apokamp) starts from the discharge channel and increases its propagation speed. The luminescence spectra show these processes to be accompanied by the emission of easily ionizable K and Na, which is consistent with data on the elemental composition of Etna samples. A hypothesis is suggested about an increase in the appearance probability of blue jets and starters over sites of high volcanic activity at altitudes of 10–18 km (at the level of the troposphere).

Progress in the Study of Transient Luminous and Atmospheric Events: A Review

Transient luminous events (TLEs) such as sprites, blue jets (BJs) and elves have been studied intensively during the last three decades, and much is now known of their properties. This progress is caused by several factors including satellite optical observations, ground-based measurements of sprite-produced electromagnetic fields, the use of high-speed video observations and telescopic cameras with high resolution that enables one to trace the dynamics of sprite and BJ development. In this paper, we review various types of TLEs, including recently discovered dancing sprites, gnomes, ultraviolet (UV) atmospheric flashes and other effects. The sprite initiation, visible evolution, streamer structure, and their relationship with intra-cloud (IC) process are discussed. Considerable study has been given to ULF/ELF measurements which can provide us with important information on the delayed sprite generation and the role played by IC processes in the perturbation of the lower ionosphere above the sprite. A set of electrodynamic and transport kinetic equations describing the TLEs are complicated because the number densities, mobilities of electrons and ions, reaction constants and other parameters are strongly dependent on altitude. Because of this, the majority of theoretical study of TLEs and other large-scale optical phenomena at high altitude are based on numerical modeling of the basic kinetic, transport and electrodynamic equations describing TLEs evolution, whereas the analytical theory remains a formidable task to be accomplished. In this paper, we review a few analytical results, which have been recently derived from simple physical models of the TLEs phenomena. In the remainder of this paper, we focus our attention on the properties of UV flashes in the mesosphere, which have been observed onboard Russian microsatellites “Universitetsky-Tanyana” and “Vernov.” Such a kind of optical flash is referred to as a transient atmospheric event, which differs from the TLEs in optical energy, duration and other parameters.

Study of Terrestrial and Cosmic UV Emissions from the International Space Station with the Mini-EUSO Telescope

Mini-EUSO is an imaging detector launched on the International Space Station on August 2019 with an unmanned Soyuz spacecraft. It is observing the Earth in a multispectral range comprising UV (300–400 nm), visible (400–780 nm) and NIR (1500–1600 nm). Mini-EUSO is accommodated on board the Russian Zvezda module, facing on a UV-transparent window in Nadir direction. The telescope main optics comprise two Fresnel lenses focusing light onto an array of 36 Hamamatsu multi-anode photomultiplier tubes, each of 64 channels for a total of 2304 pixels. In addition to the two ancillary cameras, Mini-EUSO contains an 8 × 8 array of Multi-Pixel Photon Counter SiPM. The Mini-EUSO main research objectives are the study of Ultra High Energy Cosmic Rays above 1021 eV and the search for Strange Quark Matter, even though, with its large field of view (44°), it will map an Earth ground area of 263 × 263 km2 every 2.5 µs, allowing to study several atmospheric event such as Transient Luminous Event (TLEs), meteoroids and marine bioluminescence.

Simulation of High-Altitude Discharges in a Large Plasma Facility

The most important factor determining the dynamics and structure of high-altitude discharges is the significant difference in atmospheric pressure along their length. The Sprite device was designed at the Institute of Applied Physics. It makes it possible to produce an extended concentration gradient of a neutral gas and ignite a large-scale electric discharge in it. This work presents the results of laboratory experiments simulating some properties of high-altitude discharges, primarily sprites and gigantic jets. A high-voltage pulse discharge, which is similar to sprites and gigantic jets in structure, is studied using a wide arsenal of laboratory diagnostics, including macroscopic electrophysical measurements, inductive probes for measurement of the spatial current profile, plasma microwave interferometry, and photography with nanosecond exposures. The similarity of laboratory and natural discharges is shown, and the physical problems and possible means of their solution with limited laboratory simulation are indicated.

Mini-EUSO onboard of the ISS for UV terrestrial and cosmic emission detection: space qualification and calibration

The Mini-EUSO (Multi-wavelenght Imaging New Instrument - Extreme Universe Space Observatory) telescope is designed to observe the UV emission of the Earth from the vantage point of the International Space Station (ISS) in low Earth orbit. Mini-EUSO will map the Earth in the UV range (300 - 400 nm) offering the opportunity to study a variety of atmospheric events such as Transient Luminous Events (TLEs) and meteors, as well as searching for Strange Quark Matter (SQM) and bioluminescence. The instrument comprises a compact telescope with a large field of view (44°), based on an optical system employing two Fresnel lenses for light collection, focused onto an array of 36 multi-anode photomultiplier tubes. The resulting signal is converted into digital, processed and stored via the electronics subsystems onboard. In addition to the main UV detector, Mini-EUSO contains two ancillary cameras for complementary measurements in the near infrared (1500 - 1600 nm) and visible (400 - 780 nm) range and also a SiPM (Silicon PhotoMultiplier) array which will increase the Technology Readiness Level (TRL) of this ultrafast imaging sensor.

A 3‐Year Sample of Almost 1,600 Elves Recorded Above South America by the Pierre Auger Cosmic‐Ray Observatory

AbstractElves are a class of transient luminous events, with a radial extent typically greater than 250 km, that occur in the lower ionosphere above strong electrical storms. We report the observation of 1,598 elves, from 2014 to 2016, recorded with unprecedented time resolution (100 ns) using the fluorescence detector (FD) of the Pierre Auger Cosmic‐Ray Observatory. The Auger Observatory is located in the Mendoza province of Argentina with a viewing footprint for elve observations of km , reaching areas above the Pacific and Atlantic Oceans, as well as the Córdoba region, which is known for severe convective thunderstorms. Primarily designed for ultrahigh energy cosmic‐ray observations, the Auger FD turns out to be very sensitive to the ultraviolet emission in elves. The detector features modified Schmidt optics with large apertures resulting in a field of view that spans the horizon, and year‐round operation on dark nights with low moonlight background, when the local weather is favorable. The measured light profiles of 18% of the elve events have more than one peak, compatible with intracloud activity. Within the 3‐year sample, 72% of the elves correlate with the far‐field radiation measurements of the World Wide Lightning Location Network. The Auger Observatory plans to continue operations until at least 2025, including elve observations and analysis. To the best of our knowledge, this observatory is the only facility on Earth that measures elves with year‐round operation and full horizon coverage.

Моделирование транзиентных световых явлений средней атмосферы Земли c помощью апокампического разряда

Моделирование транзиентных световых явлений средней атмосферы Земли c помощью апокампического разряда

Emerging and expanding streamer head in low-pressure air

The emergence of a streamer from an ionisation wave and its expansion are ultra-fast processes shaping the very first moments of the streamer development, and are usually accessible only by complex numerical models. In this Letter, we report experimental evidence of the emergence of a streamer from an ionisation wave in 1.3 kPa air, a laboratory analogue of early-stage streamers emerging in geophysical Blue Starters and Jets. The radially and temporally resolved electric field patterns of an expanding streamer are determined by sub-nanosecond optical emission spectroscopy. As the emerged streamer expands, the electric field decreases by a factor of 1.4 in 1 ns. We quantify the radial expansion of the streamer head and its axial acceleration, reaching the velocity of 107 m s−1. In combination with electrical measurements, the transferred charge, electron density, and mean electron energy are quantified, enabling detailed insight into this ultra-fast phenomenon at its characteristic time-scale.

Terrestrial gamma-ray flashes as the high-energy effect of tropospheric thunderstorms in near-Earth space

<p indent="0mm">Thunderstorms in the troposphere produce lightning flashes and cause charge transfer of different strength at varying spatial and temporal scales, leading to various forms of transient electromagnetic effects in the vast space above thunderstorms. In particular, normal intra-cloud (IC) lightning can generate ionizing hard X-rays and gamma rays, forming Terrestrial Gamma-ray Flashes (TGFs). We briefly summarize the progress in TGF studies that has been achieved in the past decade based on multiple space-borne platforms: (1) TGFs are usually associated with the upward negative leader during the initial stage of IC flashes and are often accompanied by relatively strong IC discharge with high peak current and large charge transfer, which is called the energetic IC pulse (EIP); (2) based on the characteristics of TGF-related radio-frequency signals, we can develop a remote sensing approach with ground-based measurements of lightning signals, thereby greatly enriching the investigation dataset of TGFs and parent thunderstorms; (3) till date, no unified mechanism for TGF production has been developed due to a lack of effective observation with respect to the source region. Thermal runaway breakdown and relativistic runaway electron breakdown are the two mainstream theories to explain TGF production. Compared with transient luminous events (TLEs; e.g., red sprites, gigantic jets, and blue jets) as the lightning-induced dielectric breakdown in the mesosphere, studies on TGFs, in terms of both observations and theoretical interpretation, lag behind the research in Europe and the USA. However, along with China’s latest progress in space detection technology (particularly the implementation of the <italic>Insight</italic> Hard X-ray Modulation Telescope (<italic>Insight</italic>-HXMT) and the Gravitational-wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM)), researchers in China desire to make steady progress in the field of TGF studies through continuous efforts in developing ground-based lightning detection techniques.

ANALYSIS OF SPRITES FROM VIDEO OBSERVATIONS MADE BY THE CROATIAN METEOR NETWORK

Sprites are optical phenomena belonging to the category of transient luminous events. They were observed using cam- eras of the Croatian Meteor Network. The sprite images extracted from the recordings from cameras located in Rijeka and Visnjan were analysed using two methods. Sprites recorded on the night of 2017/05/31 at 21:46:18.781 and 22:03:27.299 only from the camera in Rijeka were analysed using the single-station analysis method. This method works on the as- sumption that sprites occur directly above the parent lightning and uses the lightning strike location provided by the Blitzortung website together with camera recordings from one station to make the spatial positioning of the sprite pos- sible. Sprites recorded on the night of 2017/05/31 at 21:57:44.376 and 22:07:16.440 from both cameras in Rijeka and Visnjan were analysed using the double-station analysis method, which is based on the lines of sight method. Both double-station sprites were also analysed using the single-station analysis method. The resulting heights and lateral distances were compared. It was concluded that this method of single-station analysis may provide a good estimate of the sprite location in case of small lateral distances between the sprite and parent lightning, while in other cases, errors may be significant. The double-station analysis method is preferred whenever possible, as it is mathematically exact and the errors arising from it depend only on the quality of the observation data.

First 10 Months of TGF Observations by ASIM

AbstractThe Atmosphere‐Space Interactions Monitor (ASIM) was launched to the International Space Station on 2 April 2018. The ASIM payload consists of two main instruments, the Modular X‐ray and Gamma‐ray Sensor (MXGS) for imaging and spectral analysis of Terrestrial Gamma‐ray Flashes (TGFs) and the Modular Multi‐spectral Imaging Array for detection, imaging, and spectral analysis of Transient Luminous Events and lightning. ASIM is the first space mission designed for simultaneous observations of Transient Luminous Events, TGFs, and optical lightning. During the first 10 months of operation (2 June 2018 to 1 April 2019) the MXGS has observed 217 TGFs. In this paper we report several unprecedented measurements and new scientific results obtained by ASIM during this period: (1) simultaneous TGF observations by Fermi Gamma‐ray Burst Monitor and ASIM MXGS revealing the very good detection capability of ASIM MXGS and showing substructures in the TGF, (2) TGFs and Elves produced during the same lightning flash and even simultaneously have been observed, (3) first imaging of TGFs giving a unique source location, (4) strong statistical support for TGFs being produced during the upward propagation of a leader just before a large current pulse heats up the channel and emits a strong optical pulse, and (5) the t50 duration of TGFs observed from space is shorter than previously reported.

The Boltzmann Vibrational Temperature of N2 (B3Πg) Derived From ISUAL Imager Multiband Measurements of Transient Luminous Events

AbstractOne of the main challenges for the observation of a transient luminous event (TLE) is to observe TLEs in different emission bands. Here, we show TLEs recorded using the ISUAL 427.8 nm, 630 nm, N2 1P (623–750 nm) and 762‐nm‐filtered imager, and we analyze the 630‐nm‐filtered, N2 1P‐filtered, and 762‐nm‐filtered images of TLEs for estimating the N2 (B3Πg) Boltzmann vibrational temperature in comparison with the theoretical N2 1P spectrum. For ISUAL recorded sprites, the average brightness of N2 1P (I1p), 762 nm (I762), and 630 nm (I630) emission was 2.3, 0.6, and 0.02 MR. The N2 (B3Πg) vibrational temperatures (Tv) was estimated to be 2800 K, 3200 K, and 4300 K for multiband emission ratios of I630/I1p, I630/I762, and I762/I1p. For observed elves, the average brightness I1p, I762, and I630 were 170, 50, and 3 kR. The estimated Tv values were 3700 K, 3700 K, and 3800 K for ratios I630/I1p, I630/I762, and I762/I1p. For observed gigantic jets, the derived Tv values were 3000–5000 K for a ratio I762/I1p. Through N2 (B3Πg) Tv analyses from emission ratios of ISUAL multiband observation, we derived the N2 (B3Πg) vibrational temperature that ranges between 3000 and 5000 K or higher in TLEs. Accuracy and variations of derived N2 (B3Πg) Tv are also discussed while relative population of vibrational levels in the Boltzmann equilibrium are also compared with past spectra observation.

Theoretical Problems Underlying Sprite Observations of the Planned Taranis Satellite Mission

Abstract Tool for the Analysis of Radiations from lightnings and Sprites (TARANIS) is a French Space Agency’s (CNES) satellite mission planned for launch in 2020. It is designed for investigating phenomena related to thunderstorm activity, transient luminous events (TLEs) and amongst them – red sprites. The satellite is equipped with cameras, photometers, energetic particles detectors, ion probe and electromagnetic sensors of wide frequency spectrum. It will be the most versatile satellite for measuring TLEs ever sent to space. In this article, theories that are fundamental for understanding sprites and sprites-related measurements of TARANIS mission are presented. The current state of sprites phenomenology and their possible generation mechanisms are presented. The article briefly covers streamer discharges, cloud charge structure at the TLE occurrence, electric breakdown of the air and Runaway Relativistic Electron Avalanche (RREA). At the end, TARANIS mission equipment and goals that are related to presented theories are presented.

Convergence Space Experiment: Scientific Objectives, Onboard Equipment, and Methods of Solving Inverse Problems

The purpose of this research is to present a detailed description of the proposed Convergence space mission on the Russian segment of the International Space Station for the wider scientific community. The key features of the mission are (1) the necessity of creating a new type of multifrequency radio-thermal airborne complexes with a specialized set of operating frequencies and with the formation of algorithms and software for the three-dimensional recovery of the water-vapor field in the lower troposphere and for estimating the horizontal advection and convective latent heat fluxes at different altitudes and with different forms of boundaries of the investigated regions. (2) An important part of the mission is the global monitoring of optical transient activity, including lightning in cloud tropospheric systems and electric discharges in the upper atmosphere, which are accompanied by a variety of short-term optical glows, commonly called transient luminous events. A significant contribution to the elucidation of the physics and the development of models of high-altitude electric discharges is the synchronous operation of the lightning detector and gamma detector to search for and study gamma-ray bursts of terrestrial origin, including those in previously unexplored latitudes, up to ±51°. It seems that the proposed instrumental configuration and integrity of the mission, which includes the synchronous operation of devices of different ranges of electromagnetic radiation (both the microwave range and optical and gamma range) will contribute significantly to the elucidation of the physics of processes of interaction of catastrophic atmospheric phenomena of the hydrodynamic type, i.e., tropical cyclones, with the electrical activity of tropospheric cloud systems (the field of lightning discharges) and activity of high-altitude electric discharges, which, in turn, can serve as a serious experimental basis for the formation of physical ideas about the genesis of gamma-ray outbreaks of terrestrial origin.

Analysis of the Spatial Nonuniformity of the Electric Field in Spectroscopic Diagnostic Methods of Atmospheric Electricity Phenomena.

The spatial nonuniformity of the electric field in air discharges, such as streamers, can influence the accuracy of spectroscopic diagnostic methods and hence the estimation of the peak electric field. In this work, we use a self‐consistent streamer discharge model to investigate the spatial nonuniformity in streamer heads and streamer glows. We focus our analysis on air discharges at atmospheric pressure and at the low pressure of the mesosphere. This approach is useful to investigate the spatial nonuniformity of laboratory discharges as well as sprite streamers and blue jet streamers, two types of transient luminous events taking place above thunderclouds. This characterization of the spatial nonuniformity of the electric field in air discharges allows us to develop two different spectroscopic diagnostic methods to estimate the peak electric field in cold plasmas. The commonly employed method to derive the peak electric field in streamer heads underestimates the electric field by about 40–50% as a consequence of the high spatial nonuniformity of the electric field. Our diagnostic methods reduce this underestimation to about 10–20%. However, our methods are less accurate than previous methods for streamer glows, where the electric field is uniformly distributed in space. Finally, we apply our diagnostic methods to the measured optical signals in the second positive system of N2 and the first negative system of N2+ of sprites recorded by Armstrong et al. (1998, https://doi.org/10.1016/S1364-6826(98)00026-1) during the SPRITE's 1995 and 1996 campaigns.

Infrasound observations of sprites associated with winter thunderstorms in the eastern mediterranean

Abstract Sprites are transient luminous events (TLEs) that occur at mesospheric altitudes between 50 and 90 km. They last up to several milliseconds, and are caused mostly by positive lightning discharges from the thunderstorm cells below. Infrasound from sprites was first observed in detail a decade ago by a team from the French Atomic Energy Commission (CEA), as part of a renewed international interest in infrasound measurements brought about by the Comprehensive Nuclear Test Ban Treaty (CTBT) ( Farges et al., 2005 ). They used optical images of sprites obtained during the EuroSprite observation campaign in order to form the temporal and azimuthal basis necessary for searching for the infrasound signatures from these events, which appear as unique “chirp” or “inverted chirp” signatures depending on the sprite's distance from the infrasound array. In this paper we follow this methodology to see if the nascent Israeli infrasound arrays can detect these signals from sprites in the Eastern Mediterranean, for which there are nearly 8 years of winter-time optical observations. We calculated the expected arrival time of the infrasound from optically observed sprites, and then used a basic ray-tracing method in order to confirm that we were in fact able to observe several of these sprites, at various distances, exhibiting both “chirp” and “inverted chirp” signals. We then compared these observations with observations of lightning activity made by the World Wide Lightning Location Network (WWLLN).

Climatology of Transient Luminous Events and Lightning Observed Above Europe and the Mediterranean Sea

In 1999, the first sprites were observed above European thunderstorms using sensitive cameras. Since then, Eurosprite campaigns have been conducted to observe sprites and other transient luminous events (TLEs), expanding into a network covering large parts of Europe and coastal areas. In 2009 through 2013, the number of optical observations of TLEs reached a peak of 2000 per year. Because of this unprecedented number of European observations, it was possible to construct a climatology of 8394 TLEs observed above 1018 thunderstorm systems and study for the first time their distribution and seasonal cycle above Europe and parts of the Mediterranean Sea. The number of TLEs per thunderstorm was found to follow a power law, with less than 10 TLEs for 801 thunderstorms and up to 195 TLEs above the most prolific one. The majority of TLEs were classified as sprites, 641 elves, 280 halos, 70 upward lightning, 2 blue jets and 1 gigantic jet. The climatology shows intense TLE activity during summer over continental areas and in late autumn over coastal areas and sea. The two seasons peak, respectively, in August and November, separated by March and April with almost no TLEs, and a relative minimum around September. The observed TLE activity, i.e. mostly sprites, is shown to be largely consistent with lightning activity, with a 1/1000 of observed TLE-to-lightning ratio in regions with most observations. The overall behaviour is consistent among individual years, making the observed seasonal cycle a robust general feature of TLE activity above Europe.

Gigantic jet discharges evolve stepwise through the middle atmosphere

In 2002 it was discovered that a lightning discharge can rise out of the top of tropical thunderstorms and branch out spectacularly to the base of the ionosphere at 90 km altitude. Several dozens of such gigantic jets have been recorded or photographed since, but eluded capture by high-speed video cameras. Here we report on 4 gigantic jets recorded in Colombia at a temporal resolution of 200 µs to 1 ms. During the rising stage, one or more luminous steps are revealed at 32-40 km, before a continuous final jump of negative streamers to the ionosphere, starting in a bidirectional (bipolar) fashion. The subsequent trailing jet extends upward from the jump onset, with a current density well below that of lightning leaders. Magnetic field signals tracking the charge transfer and optical Geostationary Lightning Mapper data are now matched unambiguously to the precisely timed final jump process in a gigantic jet.

On negative Sprites and the Polarity Paradox

AbstractEnergetic positive and negative cloud‐to‐ground (CG) flashes are both capable of producing sprites. Negative CGs typically outnumber the positive ones by 10 to 1. However, &gt;99.9 % of reported sprites were found to be initiated by positive CGs—thus the polarity paradox. Here, sprites recorded by the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) mission were analyzed along with extremely low‐frequency band magnetic field data to resolve this paradox. Approximately twenty‐five percent of the sprites are found to be associated with negative CG lightning. “Negative” sprites mainly congregate in the latitudinal regions below 20°, while positive sprites scatter up to 50°. The ISUAL negative sprites are evidently beyond the observable ranges of the ground sites reported in previous studies. Hence, the sprite polarity paradox is likely a selection effect of the middle‐ to high‐altitudinal observation sites. The charge moment changes and accompanying transient luminous events of sprites were also examined and found to be polarity dependent.