Characteristics of lightning flashes generating sprites above storms (original) (raw)
Related papers
Coordinated observations of sprites and in-cloud lightning flash structure
Journal of Geophysical Research: Atmospheres, 2013
The temporal and spatial development of sprite-producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system (MCS) on 29 June 2011 near the Oklahoma Lightning Mapping Array (LMA). Sprites produced by a total of 26 lightning flashes were observed simultaneously on video from Bennett, Colorado and Hawley, Texas, enabling a triangulation of sprites in comparison with temporal development of parent lightning (in particular, negatively charged stepped leaders) in three-dimensional space. In general, prompt sprites produced within 20 ms after the causative stroke are less horizontally displaced (typically <30 km) from the ground stroke than delayed sprites, which usually occur over 40 ms after the stroke with significant lateral offsets (>30 km). However, both prompt and delayed sprites are usually centered within 30 km of the geometric center of relevant LMA sources (with affinity to negative stepped leaders) during the prior 100 ms interval. Multiple sprites appearing as dancing/jumping events associated with a single lightning flash could be produced either by distinct strokes of the flash, by a single stroke through a series of current surges superposed on an intense continuing current, or by both. Our observations imply that sprites elongated in one direction are sometimes linked to in-cloud leader structure with the same elongation, and sprites that were more symmetric were produced above the progression of multiple negative leaders. This suggests that the large-scale structure of sprites could be affected by the in-cloud geometry of positive charge removal. Based on an expanded dataset of 39 sprite-parent flashes by including more sprites recorded by one single camera over the same MCS, the altitude (above mean sea level, MSL) of positively charged cloud region tapped by sprite-producing strokes declined gradually from~10 km MSL (À35 C) to around 6 km MSL (À10 C) as the MCS evolved through the mature stage. On average, the positive charge removal by causative strokes of sprites observed on 29 June is centered at 3.6 km above the freezing level or at 7.9 km above ground level.
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.
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
Very low frequency sferic bursts, sprites, and their association with lightning activity
Journal of Geophysical Research, 2007
Recent observations have revealed the occurrence of burst-like VLF activity, lasting from tens of milliseconds up to a few seconds, associated with the onset of many sprites. These ''sferic bursts'' are thought to be due to the horizontal in-cloud component of lightning activity, since they have been observed to propagate only short distances (a few hundred kilometers) in the Earth-ionosphere waveguide and are generally not reported by lightning detection networks. The possible involvement of in-cloud lightning in sprite production has been previously suggested on the basis of the observed long delays and spatial displacement between causative cloud-to-ground (CG) discharges and sprite events. In this work, we investigate the association between sprites and sferic bursts using VLF data and a large set of sprite observations between 1995 and 2000. We compare the occurrence of sferic bursts in association with sprites for thousands of observations through many different dates and thunderstorms. Results indicate that sprite-causative CGs are more commonly found in association with bursts of sferic activity than those CG discharges without sprites and that, furthermore, the distribution of sferic burst VLF energy is significantly higher for sprite-associated events. We further investigate the source of these bursts by comparing VLF data to Lightning Mapping Array (LMA) data of VHF pulses due to lightning. Such comparisons show that most sferic burst events can be explained as radiation from the horizonal in-cloud components of +CG lightning, as detected by the LMA.
Monthly Weather Review, 2003
During the summer of 2000, the Severe Thunderstorm Electrification and Precipitation Study (STEPS) program deployed a three-dimensional Lightning Mapping Array (LMA) near Goodland, Kansas. Video confirmation of sprites triggered by lightning within storms traversing the LMA domain were coordinated with extremely low frequency (ELF) transient measurements in Rhode Island and North Carolina. Two techniques of estimating changes in vertical charge moment (M q) yielded averages of ϳ800 and ϳ950 C km for 13 sprite-parent positive polarity cloud-to-ground strokes (ϩCGs). Analyses of the LMA's very high frequency (VHF) lightning emissions within the two mesoscale convective systems (MCSs) show that ϩCGs did not produce sprites until the centroid of the maximum density of lightning radiation emissions dropped from the upper part of the storm (7-11.5 km AGL) to much lower altitudes (2-5 km AGL). The average height of charge removal (Z q) from 15 sprite-parent ϩCGs during the late mature phase of one MCS was 4.1 km AGL. Thus, the total charges lowered by spriteparent ϩCGs were on the order of 200 C. The regional 0ЊC isotherm was located at about 4.0 km AGL. This suggests a possible linkage between sprite-parent CGs and melting-layer/brightband charge production mechanisms in MCS stratiform precipitation regions. These cases are supportive of the conceptual MCS spriteproduction models previously proposed by two of the authors (Lyons and Williams).
Thunderstorms/Lightning Generated Sprite and Associated Phenomena
2010
The study of the thunderstorms has advanced rapidly during the past century and lots of efforts have been made towards the understanding of lightning, thunderstorms and their associated optical phenomena such as sprites, elves, blue get etc. Even though, thunderstorms and lightning are well understood, but our knowledge on sprites and associated phenomena, is limited. In this paper, we review the distribution of thunderstorm/lightning and their association with optical emissions. Detailed discussions on lightning generated sprites and various natural phenomena associated with them are also included. Recent results in this emerging field are summarized.
Terrestrial, Atmospheric and Oceanic Sciences, 2017
We examined the broadband (< 1 Hz to 30 kHz) lightning sferics associated with 395 sprites observed near North America by the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) onboard the FORMOSAT-2 satellite in a 12-year period from 2004-2015. Our analysis indicates that the ISUAL dataset contains a significant fraction (69, or ~18%) of negative sprites, which were predominantly (> 80%) observed over oceanic and coastal thunderstorms mostly in tropical areas. The mean and median of impulse charge moment change (iCMC) associated with positive (negative) sprites are +346 C km (-709 C km) and +280 C km (-649 C km), respectively. The morphology and parent lightning properties (e.g., typically with high peak currents >-80 kA and large iCMCs >-300 C km) of negative sprites observed by the ISUAL are generally consistent with that documented in ground-based observations, but the ISUAL dataset does imply that sprites are sometimes produced by negative strokes with sub-critical iCMCs (less than-300 C km). Consequently, the future survey of global occurrence of sprites is desired to be based on complementary ground and space-borne observations.
Evidence for continuing current in sprite-producing cloud-to-ground lightning
Geophysical Research Letters, 1996
Radio atmospherics launched by spriteproducing positive cloud-to-ground lightning flashes and observed at Palmer Station, Antarctica, exhibit large ELF slow tails following the initial VLF portion, indicating the presence of continuing currents in the source lightning flashes. niometry method is based on the Fourier Transform of a function whose real part is BNS and whose imaginary part is BEv\,. The phase of the transform represents the direction of arrival as a function of frequency. The arrival azimuth of a given sferic is computed over the 5.5 kHz to 9.5 kHz band, weighted by the magnitude of the signal at each frequency. This frequency range is selected as one in which multiple cycles of the waveform are available within the duration of
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