Optical observations of transient luminous events associated with winter thunderstorms near the coast of Israel (original) (raw)
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ELF transients associated with sprites and elves in eastern Mediterranean winter thunderstorms
Journal of Atmospheric and Solar-terrestrial Physics, 2007
During the northern hemisphere winter of 2005-2006, transient luminous events (TLEs) known as 'sprites' and 'elves' were imaged over thunderstorm cells in the eastern Mediterranean. Simultaneously, extremely low frequency (ELF) data (ELF: 3-3000 Hz) were recorded at two observation stations in Israel and Hungary in order to qualify and quantify parameters of the parent lightning discharge associated with the transient optical emissions in the upper atmosphere. In this study, we found that for 87% (Israel) and 77% (Hungary) of optically observed TLEs an intense ELF transient event was recorded. These stations are located some 500 and 2100 km, respectively, from the region of the TLEs. All ELF transients that were associated with TLEs were caused by lightning discharges with positive polarity. Calculation of the charge moment change showed values between 600 and 2800 C km with a peak around 1000 C km. Additionally, the time delay between the +CG and ensuing sprite was 76734 ms and it was displaced up to 50 km from its parent CG.
Journal of Atmospheric and Solar-Terrestrial Physics, 2007
Sprites are newly discovered optical emissions in the mesosphere over large thunderstorms. This paper is the observational summary of winter sprites in the Hokuriku area of Japan and their parent lightning in the winter of 2004/ 2005, by using the coordinated optical and electromagnetic (VHF and ELF) measurements in Japan. As the results of optical observations at two stations, we have found that this campaign has yielded a variety of sprite shapes; V-angle shaped structures have been often observed (25%) in addition to columnar structures familiar for us. All of the sprite events are found to be associated with þCG lightning, as seen from the macroscopic information by ELF data at Moshiri. However, examining the microscopic properties of parent lightning as seen from the VHF SAFIR lightning detection network, has suggested very complicated characteristics of parent lightning discharges inducing sprites, as compared with the ELF data. One half of the sprite events are also found to be associated with þCG by the SAFIR observation, but another half has yielded rather new results as compared with earlier results. Four events are definitely associated with ÀCG and the remaining three events, inter-cloud flashes. The overall picture for Japanese winter sprites and their parent lightning discharges, is significantly different from that for the summer-time, continental sprites. This is indicative of complexity of winter lightning in the Hokuriku area of Japan and this would provide new information on the sprite generation mechanism. r
2000
A six year record of optical observations of lightning-induced mesospheric transient luminous events (TLEs) is available from the Yucca Ridge Field Station (YRFS) near Ft. Collins, CO. Climatological analyses reveal sprites and elves occur in a variety of convective storm types, but principally mesoscale convective systems (MCSs) and squall lines. Severe supercell storms rarely produce TLEs, except during their dissipating
Geophysical Research Letters, 2007
1] During the winter of 2005-6, optical ground-based observations were performed to detect transient luminous events (TLEs) above winter thunderstorms in the vicinity of Israel and the eastern coastline of the Mediterranean Sea. Two sites were used: the Tel Aviv University (TAU) campus in Tel-Aviv (32.5N, 34.5E) and the Wise astronomical observatory in the Negev desert (30.6N, 34.76E). We also conducted ELF and VLF electromagnetic measurements from the TAU array in southern Israel. In 4 different winter storms we detected 30 events: 26 sprites and 4 elves. The detection ranges varied from 250 to 450 km. Sprites were found to be produced exclusively by +CGs that can be traced to active cells with a vertical dimension of 5 -7 km and cloud top temperature $À40°C, embedded in a much larger matrix of stratiform cloudiness. This configuration closely resembles the conditions for winter sprites in the Hokuriku region of Japan. Citation: Ganot, M.
Surveys in Geophysics
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 5 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 10 shows intense TLE activity during summer over continental areas, and in late autumn over coastal 1 vised manuscript with changes highlighted Click here to access/download;attachment to manuscript;Arnone2019_SG_revised_manuscript_RM_changes_ lick here to view linked References 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 behavior is consistent among individual years, making the observed seasonal cycle a robust general feature of TLE activity above Europe. Article Highlights • Detailed climatological study of TLEs and lightning above Europe produced for the first time • Seasonal cycle of TLEs and lightning with two active seasons in summer over land and autumn over sea and coastal areas • Power law distribution of number of TLEs per thunderstorm Keywords Thunderstorms, lightning, transient luminous events, ground-based observations, Europe, climatology. 1 Introduction 1.1 Transient luminous events Three decades ago, a test low-light camera recorded a sprite (Franz et al., 1990), a spectacular discharge extending for tens of km above a thunderstorm. It was the first discovery of a whole family of upper atmosphere electrical processes, collectively known as transient luminous events (TLEs-see
Characteristics of lightning flashes generating sprites above storms
E3S Web of Conferences, 2016
Sprites are Transient Luminous Events (TLEs) that can extend vertically from 40 to 90 km and horizontally over several tens of km to form clusters of individual or multiple column or/and carrot-shaped luminous elements. They can even extend over more than 100 km in the form of sequential luminous emissions that are called "dancing sprites". Their optical detection and other parameters describing the storm and the lightning activity associated allow us to understand the conditions of their production and their links with the lightning activity. Our observations confirm some characteristics of the sprites and put forward others: (i) the sprites are essentially produced above the stratiform region of the Mesoscale Convective Systems after positive cloud-to-ground lightning flashes that produce large Charge Moment Change (CMC), with a shorter delay if the impulsive CMC (iCMC) is larger. (ii) The dancing sprites reflect the timing and the location of the successive lightning strokes that generate them. (iii) The sprite elements can be shifted from the stroke location when their delay is large. (iv) Bright sprites produce current signatures in ELF radiation a few milliseconds (<5 ms) after the positive strokes that generate them.
We report synchronized optical observations of sprites in Israel during the winters of 2006/7–2007/8. Based on several events, we suggest that the elements of columniform sprites are organized in spaced intervals on the circumference of a circle centered directly above, or a little offset, to the vertical direction from the parent lightning. In 2D images most of the cases show columns to be arranged in highly eccentric elliptical forms or in straight rows. The analysis of the optical images provided the geometrical dimensions of the columns and their spatial organization. We used an electrostatic model of the QE field with reasonable assumptions on the location and magnitude of the cloud charge center, constrained by ELF evaluation of the Charge Moment Change in the parent flash, to show that the observed diameter of the columnar arrangement closely matches the conventional breakdown field line contour at the same altitude.
Observations of the relationship between sprite morphology and in-cloud lightning processes
Journal of Geophysical Research, 2006
, 15 sprites were captured by a LLTV camera mounted at the observatory on Pic du Midi in the French Pyrénées. Simultaneous observations of cloud-to-ground (CG) and intracloud (IC) lightning activity from two independent lightning detection systems and a broadband ELF/VLF receiver allow a detailed study of the relationship between electrical activity in a thunderstorm and the sprites generated in the mesosphere above. Results suggest that positive CG and IC lightning differ for the two types of sprites most frequently observed, the carrot-and column-shaped sprites. Column sprites occur after a short delay (<30 ms) from the causative +CG and are associated with little VHF activity, suggesting no direct IC action on the charge transfer process. On the other hand, carrot sprites are delayed up to about 200 ms relative to their causative +CG stroke and are accompanied by a burst of VHF activity starting 25-75 ms before the CG stroke. While column sprites associate with short-lasting (less than 30 ms) ELF/VLF sferics, carrot sprites associate with bursts of sferics initiating at the time of the causative +CG discharge and persisting for 50 to 250 ms, indicating extensive in-cloud activity. One carrot event was found to be preceded by vigorous IC activity and a strong, long-lived cluster of ELF/VLF sferics but lacking a +CG. The observations of ELF/VLF sferic clusters associated with lightning and sprites form the basis for a discussion of the reliability of lightning detection systems based on VHF interferometry.
Space Science Reviews, 2011
This paper presents a literature survey on the recent developments related to experimental and modeling studies of transient luminous events (TLEs) in the middle atmosphere termed elves, sprites and jets that are produced in association with thunderstorm activity at tropospheric altitudes. The primary emphasis is placed on publications that appeared in refereed literature starting from year 2008 and up to the present date. The survey covers general phenomenology of TLEs and their relationships to characteristics of individual thunderstorms and lightning, physical mechanisms and modeling of TLEs, past, present and future orbital observations of TLEs, and their chemical, energetic and electric effects on local and global scales.