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Serge Soula - One of the best experts on this subject based on the ideXlab platform.
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Dancing Sprites Above a Lightning Mapping Array - an analysis of the storm and flash/Sprite developments
2021Co-Authors: Maja Tomicic, Serge Soula, Thomas Farges, Serge Prieur, Eric DeferAbstract:<p>This study is a multi-instrumental analysis of a ~20-hour duration northwestern Mediterranean storm on September 21, 2019 that produced 21 Sprites recorded with a video camera, of which 19 (90 %) were dancing Sprites. A dancing Sprite is a phenomenon in which sequences of Sprites appear in succession with time intervals of no more than a few hundred milliseconds. For the most part, the individual Sprites are a consequence of discrete strokes from one extended lightning flash. In this case, we find that 87.5% of the Sprite sequences were triggered by distinct positive cloud-to-ground (+CG) strokes. The time between successive Sprite parent (SP)+CG strokes within the same dancing Sprite was between 40 and 516 ms, and the distance ranged between 2 and 87 km. The storm size and vertical development were analyzed from the infrared radiometer onboard Meteosat Second Generation satellite and the lightning activity was documented with several lightning location systems (LLS): the French LF network (M&#233;t&#233;orage), the GLD360 network operated by Vaisala company, the VHF SAETTA Lightning Mapping Array (LMA) system located in Corsica. Additionally, the vertical electric field at the time of the dancing Sprites was measured with a broadband ELF vertical dipole whip antenna ~700 km away from the storm. The SAETTA LMA allows to map the SP+CG flashes in their both full extent and temporal evolution, and to infer the charge structure of the parent storm. We show that the SP+CG flashes followed a common propagation: they originated from the convective and very electrically active regions of the storm, and then escaped and extended horizontally far (tens of km) into the stratiform cloud region. Most of the Sprites were triggered by +CG strokes in the stratiform region often following flash development resembling cutoff of a long negative leader. Additionally, we present a detailed analysis of two dancing Sprite events in which the SP+CGs triggered new bidirectional breakdown with fast moving leaders that extended into the stratiform cloud region and resulted in new SP+CG strokes. In both events, we find in both LLS and ELF vertical electric field records, that the last Sprite sequence was triggered by three almost simultaneous +CG strokes.</p>
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On the speed of Sprite initiation
2014 XXXIth URSI General Assembly and Scientific Symposium (URSI GASS), 2014Co-Authors: Martin Füllekrug, Andrew Mezentsev, Zhongjian Liu, Serge SoulaAbstract:Sprites are composed of individual streamer discharges (e.g., Pasko, 2010) which split into streamer tips (McHarg et al., 2010) with diameters ∼50–100 m at ∼60–80 km height (Kanmae et al., 2012). The Sprite luminosity coincides in time and space with extremely low frequency electromagnetic radiation
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multi instrumental analysis of large Sprite events and their producing storm in southern france
Atmospheric Research, 2014Co-Authors: Serge Soula, Martin Füllekrug, József Bór, Thomas Farges, Joan Montanya, F Iacovella, O Van Der Velde, Jeanfrancois Georgis, S Naitamor, J M MartinAbstract:Abstract During the night of 01–02 September, 2009, seventeen distinct Sprite events including 3 halos were observed above a storm in north-western Mediterranean Sea, with a video camera at Pic du Midi (42.93N; 0.14E; 2877 m). The Sprites occurred at distances between 280 and 390 km which are estimated based on their parent CG location. The MCS-type storm was characterized by a trailing-stratiform structure and a very circular shape with a size of about 70,000 km 2 (cloud top temperature lower than − 35 °C) when the TLEs were observed. The cloud to ground (CG) flash rate was large (45 min − 1 ) one hour before the TLE observation and very low ( − 1 ) during it. Out of the 17 Sprite events, 15 parent + CG (P + CG) strokes have been identified and their average peak current is 87 kA (67 kA for the 14 events without halo), while the associated charge moment changes (CMC) that could be determined, range from 424 to 2088 ± 20% C km. Several 2-second videos contain multiple Sprite events: one with four events, one with three events and three with two events. Column and carrot type Sprites are identified, either together or separately. All P + CG strokes are clearly located within the stratiform region of the storm and the second P + CG stroke of a multiple event is back within the stratiform region. Groups of large and bright carrots reach ~ 70 km height and ~ 80 km horizontal extent. These groups are associated with a second pulse of electric field radiation in the ELF range which occurs ~ 5 ms after the P + CG stroke and exhibits the same polarity, which is evidence for current in the Sprite body. VLF perturbations associated with the Sprite events were recorded with a station in Algiers.
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High‐speed intensified video recordings of Sprites and elves over the western Mediterranean Sea during winter thunderstorms
Journal of Geophysical Research: Space Physics, 2010Co-Authors: Joan Montanya, O Van Der Velde, D. Romero, V. March, G. Solà, M. Arrayas, J.l. Trueba, V. Reglero, Nicolau Pineda, Serge SoulaAbstract:We report the first intensified high‐speed video images of elves, Sprites, and halos observed in Europe. All the events corresponded to winter season thunderstorms over the Mediterranean Sea. The observations comprise many elves generated by both cloud‐to‐ground lightning current polarities. In 8 of the 14 Sprite observations we observed an elve previous to the Sprite. In three cases we observed also an elve quickly followed by a halo and a Sprite. In several observations we observed lightning light before the mesospheric transient luminous event. We present a case where the lightning from cloud tops was visible during the entire event. Thanks to the high‐speed videos and their resolution and low intensifier phosphor persistence we analyzed the timing distribution of the development phase of Sprite elements, the persisting luminosity phase, and the total duration. Finally, we summarize one particular observation where a streamer collides and bounces with a previous formed column; it may be a new phenomenon of collision between an existing column body that interacts with a later streamer point‐like tip which is not merged and attached.
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analysis of thunderstorm and lightning activity associated with Sprites observed during the euroSprite campaigns two case studies
Atmospheric Research, 2009Co-Authors: Serge Soula, Torsten Neubert, Oscar Van Der Velde, Joan Montanya, Olivier Chanrion, Michal GanotAbstract:During the summers of 2003 to 2006 Sprites were observed over thunderstorms in France by cameras on mountain tops in Southern France. The observations were part of a larger coordinated effort, the EuroSprite campaigns, with data collected simultaneously from other sources including the French radar network for precipitation structure, Meteosat with images of cloud top temperature and the Meteorage network for detection of cloud-to-ground (CG) flash activity. In this paper two storms are analyzed, each producing 27 Sprite events. Both storms were identified as Mesoscale Convective Systems (MCS) with a trailing stratiform configuration (ST) and reaching a maximum cloud area of ~ 120,000 km2. Most of the Sprites were produced while the stratiform area was clearly developed and during periods of substantial increase of rainfall in regions with radar reflectivity between 30 and 40 dBZ. The Sprite-producing periods followed a maximum in the CG lightning activity and were characterized by a low CG flash rate with a high proportion of + CG flashes, typically around 50%. All Sprites were associated with + CGs except one which was observed after a − CG as detected by the Meteorage network. This − CG was estimated to have − 800 C km charge moment change. The peak current of Sprite-producing + CG (SP + CG) flashes was twice the average value of + CGs and close to 60 kA with little variation between the periods of Sprite activity. The SP + CG flashes were further characterized by short time intervals before a subsequent CG flash (median value < 0.5 s) and with clusters of several CG flashes which suggest that SP + CG flashes often are part of multi-CG flash processes. One case of a lightning process associated with a Sprite consisted of 7 CG flashes.
Davis D. Sentman - One of the best experts on this subject based on the ideXlab platform.
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The 762 nm emissions of Sprites
Journal of Geophysical Research, 2011Co-Authors: Cheng Ling Kuo, Davis D. Sentman, Rue-ron Hsu, A. A. Chen, Harald U. Frey, Lijou Lee, Taiyin Huang, Shu Chun Chang, S. B. MendeAbstract:[1] We report the 762 nm emissions in Sprites recorded by the ISUAL experiment onboard the FORMOSAT-2 satellite. The 762 nm imager filter is centered at 763.3 nm with a 7 nm bandwidth at 50% transmittance. Sprite emissions in this passband include the N2 first positive (1PN2) bands, (2, 0) and (3, 1), the O2 atmospheric (atm) band (0, 0), and the hydroxyl (4, 0) emissions. Because these mixed emissions cannot be resolved in the 762 nm narrowband filter, a zero-dimensional plasma chemistry model is used to estimate the expected relative intensities of these emission bands in Sprites. The computed 1PN2 brightness in a single streamer is 1.4 MR and 2.6 kR for the O2 atm band emissions at frame integration times of 30 ms. In the 762 nm passband, the 1PN2 emissions are the dominant emissions in Sprites, and the ratio of 1PN2 to O2 atmospheric emissions is ∼500, while the hydroxyl emissions can be neglected. In this ISUAL 762 nm campaign, the brightest Sprite out of the four recorded events has possible O2 atm band emissions that lasted more than 90 ms, and its observed brightness is consistent with the model prediction. Even though the lightning 762 nm emissions are strongly absorbed by O2 below 60 km, the ISUAL observed parent lightning emissions in this passband are still more than a factor of two brighter than those from ISUAL observed Sprites. Hence for spacecraft nadir TLE detection missions, 762 nm bands may not be used as the sole signature to identify Sprites, and auxiliary emission bands are needed.
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simultaneous observations of mesospheric gravity waves and Sprites generated by a midwestern thunderstorm
Journal of Atmospheric and Solar-Terrestrial Physics, 2003Co-Authors: Davis D. Sentman, D. R. Moudry, H C Stenbaeknielsen, E M Wescott, Richard H Picard, Jeremy R Winick, E M Dewan, F Sao T Sabbas, M J Heavner, J S MorrillAbstract:from a central excitation region directly above the storm. During the initial stages of the storm outwardly expanding waves possessed a period of � ≈10 min and wavelength � ≈50 km. Over a 1 h interval the waves gradually changed to longer period � ≈11 min and shorter wavelength � ≈40 km. Over the full 2 h observation time, about two dozen bright Sprites generated by the underlying thunderstorm were recorded near the center of the outwardly radiating gravity wave pattern. No distinctive OH brightness signatures uniquely associated with the Sprites were detected at the level of 2% of the ambient background brightness, establishing an associated upper limit of approximately A T . 0:5 K for a neutral temperature perturbation over the volume of the Sprites. The corresponding total thermal energy deposited by the Sprite is bounded by these measurements to be less than ∼1 GJ. This value is well above the total energy deposited into the medium by the Sprite, estimated by several independent methods to be on the order of ∼1–10 MJ. c
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Imaging of elves, halos and Sprite initiation at time resolution
Journal of Atmospheric and Solar-Terrestrial Physics, 2003Co-Authors: D. R. Moudry, Hans C. Stenbaek-nielsen, Davis D. Sentman, Eugene M. WescottAbstract:Abstract Elves, halos and Sprites were observed during August 1999 with a 1 ms high speed imager. The higher time resolution compared to conventional television cameras (17 or 20 ms ) allowed excellent images of the three phenomena temporally separate from each other to be obtained. Analysis of images of elves and halos indicates that the causal lightning-generated electromagnetic pulse and quasi-electro static fields are homogeneous and any small-scale (sub- 10 km ) structure, if visible, is most likely due to a structured atmosphere. Observations of Sprites initiated to the side of a halo, without a halo, and from beads left over from a previous Sprite, respectively, all suggest sub-pixel ( km ) background structures in atmospheric pressure or composition as being the dominant factors in determining the Sprite “seed” location, or site of Sprite initiation.
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Velocities of Sprite tendrils
Geophysical Research Letters, 2002Co-Authors: D. R. Moudry, Hans C. Stenbaek-nielsen, Davis D. Sentman, Eugene M. WescottAbstract:[1] The University of Alaska deployed a high speed (1000 fps) camera at the Wyoming Infrared Observatory to observe Sprites over Midwest U.S. thunderstorms as part of the 1999 NASA Sprites Balloon Campaign. Here we report on the velocity of development of downward spatial structures known as tendrils in several Sprite events recorded during a large thunderstorm over eastern Nebraska the night of 18 August 1999. Downward tendril development occurred at velocities that varied by more than two orders of magnitude, ranging from ∼105 to ≥3 × 107 m/s. The tendrils progressed through multiple velocity regimes, typically in the order fast-slow or slow-fast-slow. Examples are presented of multiple sets of temporally distinct tendrils that develop from the same Sprite event and tendrils that have a horizontal component of expansion.
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Mesospheric Sprite current triangulation
Journal of Geophysical Research, 2001Co-Authors: Martin Füllekrug, D. R. Moudry, Graham Dawes, Davis D. SentmanAbstract:A network of three time-synchronized high-precision induction coil magnetometers is installed in North America to measure Sprite-associated lightning flash waveforms in the frequency range 0.1–1000 Hz during the Energetics of Upper Atmosphere Excitation by Lightning, 1998, Sprite campaign in July 1998. Simultaneous intensified video observations on board an aircraft are used to investigate 16 Sprites with long time delays >33.33 ms relative to the parent lightning discharge reported by the National Lightning Detection Network. Three different long-delayed Sprite-associated waveforms can be distinguished: 38% do not exhibit any significant magnetic intensity variation, 25% exhibit slow variations ∼100 ms, and 25% exhibit short pulses ∼4 ms. The source locations of the Sprite-associated short pulses are triangulated by use of arrival time difference analysis. One source location exhibits a substantial spatial displacement ∼60 km relative to the parent lightning discharge, in agreement with the azimuths of Sprite luminosity edges determined from the corresponding background star field of the video observations on board the aircraft. It is concluded from the temporal and spatial coincidence of the secondary short pulse and the Sprite luminosity that this particular Sprite is associated with current in the mesosphere.
S. Soula - One of the best experts on this subject based on the ideXlab platform.
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Spatial and temporal evolution of horizontally extensive lightning discharges associated with Sprite-producing positive cloud-to-ground flashes in northeastern Spain.
Journal of Geophysical Research, 2010Co-Authors: O.a. Van Der Velde, J. Montanya, S. Soula, N. Pineda, J. BechAbstract:During the evening of 6 August 2008, a small mesoscale convective system (MCS) entered the area of radar and 2-D interferometric lightning detection system coverage in northeastern Spain and produced 17 Sprites recorded by a camera at only 95–180 km distance. This study presents an analysis of the in-cloud component of the Sprite-associated lightning flashes and those of other flashes. The analysis focuses on the horizontal development of Sprite-producing lightning by discussing three examples, divided into the periods before the positive cloud-to-ground flash (+CG), between +CG and the end of the Sprite, and the period after the Sprite. Location and horizontal size of Sprites appear to be well explained by the temporal and spatial development of the lightning path. The majority of Sprite-producing discharges started directly at the rear side of developing and mature convective cores within the decaying MCS, either with the +CG or with preceding negative leaders. The +CG started a burst of VHF sources during which the Sprite developed. Delayed carrot Sprites developed after a secondary, smaller burst and were well collocated with the burst toward the rear of the MCS. The order of development of elements in a grouped Sprite followed the direction of lightning propagation during the burst stage. The second part of the analysis concentrates on the metrics of sequences of VHF sources and shows that Sprites are indeed produced by the largest, longest lasting discharges with particularly large line-perpendicular dimensions (37 km median compared with 11 km for +CG >25 kA).
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High-speed intensified video recordings of Sprites and elves over the western Mediterranean Sea during winter thunderstorms.
Journal of Geophysical Research Space Physics, 2010Co-Authors: J. Montanya, N. Pineda, O Van Der Velde, D. Romero, V. March, G. Solà, M. Arrayas, J.l. Trueba, V. Reglero, S. SoulaAbstract:We report the first intensified high‐speed video images of elves, Sprites, and halos observed in Europe. All the events corresponded to winter season thunderstorms over the Mediterranean Sea. The observations comprise many elves generated by both cloud‐to‐ground lightning current polarities. In 8 of the 14 Sprite observations we observed an elve previous to the Sprite. In three cases we observed also an elve quickly followed by a halo and a Sprite. In several observations we observed lightning light before the mesospheric transient luminous event. We present a case where the lightning from cloud tops was visible during the entire event. Thanks to the high‐speed videos and their resolution and low intensifier phosphor persistence we analyzed the timing distribution of the development phase of Sprite elements, the persisting luminosity phase, and the total duration. Finally, we summarize one particular observation where a streamer collides and bounces with a previous formed column; it may be a new phenomenon of collision between an existing column body that interacts with a later streamer point‐like tip which is not merged and attached.
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Analysis of thunderstorm and lightning activity associated with Sprites observed during the EuroSprite campaigns:Two case studies.
Atmospheric Research, 2009Co-Authors: S. Soula, T. Neubert, O. Chanrion, J. Montanya, Van Der Velde O., Michal GanotAbstract:During the summers of 2003 to 2006 Sprites were observed over thunderstorms in France by cameras on mountain tops in Southern France. The observations were part of a larger coordinated effort, the EuroSprite campaigns, with data collected simultaneously from other sources including the French radar network for precipitation structure, Meteosat with images of cloud top temperature and the Météorage network for detection of cloud-to-ground (CG) flash activity. In this paper two storms are analyzed, each producing 27 Sprite events. Both storms were identified as Mesoscale Convective Systems (MCS) with a trailing stratiform configuration (ST) and reaching a maximum cloud area of ~ 120,000 km2. Most of the Sprites were produced while the stratiform area was clearly developed and during periods of substantial increase of rainfall in regions with radar reflectivity between 30 and 40 dBZ. The Sprite-producing periods followed a maximum in the CG lightning activity and were characterized by a low CG flash rate with a high proportion of + CG flashes, typically around 50%. All Sprites were associated with + CGs except one which was observed after a − CG as detected by the Météorage network. This − CG was estimated to have − 800 C km charge moment change. The peak current of Sprite-producing + CG (SP + CG) flashes was twice the average value of + CGs and close to 60 kA with little variation between the periods of Sprite activity. The SP + CG flashes were further characterized by short time intervals before a subsequent CG flash (median value < 0.5 s) and with clusters of several CG flashes which suggest that SP + CG flashes often are part of multi-CG flash processes. One case of a lightning process associated with a Sprite consisted of 7 CG flashes.
Victor P. Pasko - One of the best experts on this subject based on the ideXlab platform.
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Mechanisms of Sprite initiation, morphology, and lightning polarity asymmetry
2014 XXXIth URSI General Assembly and Scientific Symposium (URSI GASS), 2014Co-Authors: Jianqi Qin, Sébastien Celestin, Victor P. Pasko, Steven A. Cummer, Matthew G. Mcharg, Hans C. Stenbaek-nielsenAbstract:Sprites are spectacular optical emissions in the mesosphere induced by transient lightning electric fields above thunderstorms. Recently, significant efforts have been devoted to the understanding of the inception mechanism of Sprite streamers, the origin of different Sprite morphologies, and the lightning polarity asymmetry in producing Sprites. In this paper, we present a combination of observational and modeling results explaining the physical parameters and processes that are important for the resolution of these outstanding issues. We first emphasize the presence of plasma inhomogeneities in the lower ionosphere as a necessary condition for the initiation of Sprite streamers. Then we explain the relation between Sprite morphology and the characteristics of the causative lightning discharges using plasma fluid modeling results in comparison with optical and radio observations. Finally, we discuss the critical factors that account for the lightning polarity asymmetry in producing Sprites.
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Dependence of positive and negative Sprite morphology on lightning characteristics and upper atmospheric ambient conditions
Journal of Geophysical Research Space Physics, 2013Co-Authors: Jianqi Qin, Sébastien Celestin, Victor P. PaskoAbstract:Carrot Sprites, exhibiting both upward and downward propagating streamers, and columniform Sprites, characterized by predominantly vertical downward streamers, represent two distinct morphological classes of lightning-driven transient luminous events in the upper atmosphere. It is found that positive cloud-to-ground lightning discharges (+CGs) associated with large charge moment changes (QhQ) tend to produce carrot Sprites with the presence of a mesospheric region where the electric field exceeds the value 0.8Ek and persists for >~2 ms, whereas those associated with small QhQ are only able to produce columniform Sprites. Columniform Sprites may also appear in the periphery of a Sprite halo produced by +CGs associated with large QhQ. For a sufficiently large QhQ, the time dynamics of the QhQ determines the specific shape of the carrot Sprites. In the case when the sufficiently large QhQ is produced mainly by an impulsive return stroke, strong electric field is produced at high altitudes and manifests as a bright halo, and the corresponding conductivity enhancement lowers/enhances the probability of streamer initiation inside/below the Sprite halo. A more impulsive return stroke leads to a more significant conductivity enhancement (i.e., a brighter halo). This conductivity enhancement also leads to fast decay and termination of the upper diffuse region of carrot Sprites because it effectively screens out the electric field at high altitudes. On the contrary, if the sufficiently large QhQ is produced by a weak return stroke (i.e., a dim halo) accompanied by intense continuing current, the lightning-induced electric field at high altitudes persists at a level that is comparable to Ek, and therefore an extensive upper diffuse region can develop. Furthermore, we demonstrate that `negative Sprites' (produced by -CGs) should be necessarily carrot Sprites and most likely accompanied by a detectable halo, since the initiation of upward positive streamers is always easier than that of downward negative streamers, and -CGs are usually associated with impulsive return stroke with no continuing current. We also conjecture that in some cases, fast decaying single-headed upward positive streamers produced by -CGs may appear as bright spots/patches. We show that the threshold charge moment changes of positive and negative Sprites are, respectively, ~320 and ~500 C km under typical nighttime conditions assumed in this study. These different initiation thresholds, along with the different applied electric field required for stable propagation of positive and negative streamers and the fact that +CGs much more frequently produce large charge moment changes, represent three major factors in the polarity asymmetry of +CGs and -CGs in producing Sprite streamers. We further demonstrate that lower mesospheric ambient conductivity leads to smaller threshold charge moment change required for the production of carrot Sprites. We suggest that geographical and temporal conductivity variations in the lower ionosphere documented in earlier studies, along with the seasonal and inter-annual variations of thunderstorm activity that lead to different lightning characteristics in the troposphere, account for the different morphological features of Sprites observed in different observation campaigns.
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Toward Better Understanding of Sprite Streamers: Initiation, Morphology, and Polarity Asymmetry
Surveys in Geophysics, 2013Co-Authors: Victor P. Pasko, Jianqi Qin, Sébastien CelestinAbstract:The goal of this tutorial talk is to provide an introduction to physics of gas discharges as relevant to interpretation of morphological features observed in large scale electrical discharges termed Sprites and Sprite halos that are produced at mesospheric and lower ionospheric altitudes in the Earth's atmosphere by lightning. We will introduce parameters typically used for quantitative description of electron avalanches and discuss importance of space charge effects on different spatial scales, including Sprite halos (exhibiting 10s of km transverse extents) and Sprite streamers (requiring sub-meter resolution for accurate description). The special emphasis will be placed on interpretation of initiation and development of Sprite streamers observed in high-speed video observations and critical review of the most recent modeling efforts related to these observations.
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Mechanism of column and carrot Sprites derived from optical and radio observations
Geophysical Research Letters, 2013Co-Authors: Jianqi Qin, Sébastien Celestin, Victor P. Pasko, Steven Cummer, Matthew Mcharg, Hans Stenbaek-nielsenAbstract:[1] The lightning current waveforms observed simultaneously with high-speed video records of a column and a carrot Sprite event are incorporated in a plasma fluid model to provide quantitative explanation of these two distinct morphological classes of transient luminous events. We calculate the strength of the lightning-induced electric field at Sprite altitudes using a time integral of the ionization frequency R t 0 i (E/N)dt. For the studied two events, modeling results indicate that these integral values never exceed 18 in the lower ionosphere, which is the minimum value required for the initiation of streamers from single seed electrons according to the Raether-Meek criterion. It is therefore suggested that the presence of electron inhomogeneities is a necessary condition for the initiation of Sprite streamers. It is further demonstrated using streamer modeling that a minimum value of the integral 10 is necessary to initiate upward negative streamers from inhomogeneities, corresponding to a minimum charge moment change of 500 C km under typical nighttime conditions. If the integral values in the entire upper atmosphere are smaller than 10, only column Sprites can be produced, dominated by downward positive streamers. Citation: Qin, (2013), Mechanism of column and carrot Sprites derived from optical and radio observations , Geophys.
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Sprite Streamers Imaged at Different Exposure Times
IEEE Transactions on Plasma Science, 2011Co-Authors: Ningyu Liu, Hans C. Stenbaek-nielsen, Victor P. Pasko, Matthew G. MchargAbstract:This paper investigates the appearance of Sprite streamer discharges imaged at different exposure times. Both observational and modeling results are presented to illustrate that the formation of luminous filamentary channels in Sprites is caused by bright and fast-moving Sprite streamer heads.
Masashi Hayakawa - One of the best experts on this subject based on the ideXlab platform.
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Progress in the Study of Transient Luminous and Atmospheric Events: A Review
Surveys in Geophysics, 2020Co-Authors: Vadim V. Surkov, Masashi HayakawaAbstract: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.
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On the fine structure of thunderstorms leading to the generation of Sprites and elves: Fractal analysis
Journal of Geophysical Research: Atmospheres, 2005Co-Authors: Masashi Hayakawa, T. Nakamura, D. I. Iudin, Koichiro Michimoto, Tomoyuki Suzuki, T. Hanada, T. ShimuraAbstract:[1] The fine structure of convective clouds leading to the generation of Sprites and elves has been studied using radar images. Sprites and elves were observed on two days, 19 December 1998 and 27 January 1999, in lightning during winter thunderstorms on the Sea of Japan. Fractal analyses of the radar images (as an ensemble and as separate clusters) for those two days have been performed with respect to the occurrence of Sprites and elves. We have found that a Sprite and/or an elve is triggered when and just after the image cluster maximum size increases to a certain value (∼150 km) and the ensemble fractal dimension approaches a threshold (i.e., percolation threshold).
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Observation of Sprites over the Sea of Japan and conditions for lightning‐induced Sprites in winter
Journal of Geophysical Research, 2004Co-Authors: Masashi Hayakawa, T. Nakamura, Y. Hobara, Earle WilliamsAbstract:[1] We have succeeded in observing Sprites for winter lightning in the Hokuriku area (Japan Sea side) of Japan in the winter of 2001/2002. The optical results on 3 days are compared with the corresponding characteristics of parent (causative) lightning with particular attention to the significant differences between Hokuriku winter lightning and the more widely studied continental lightning. Despite significant differences with Hokuriku winter lightning, we have found nearly the same Sprite properties as already observed in the U.S. continent with a significant difference (simpler shape for Hokuriku winter Sprite). Then, we have also discussed the criteria for Sprite occurrence. Specifically, two similar criteria are found: (1) cloud-to-ground discharges of positive polarity and (2) the presence of a certain threshold in vertical charge moment (200–300 C km) (roughly consistent with that for the U.S. continent). Mesoscale convective systems are not necessary to store the charge necessary for Sprites, but the parent Hokuriku winter clouds are substantially smaller than the minimum scale for Sprite occurrence in the continental lightning; however, it is larger in area than ordinary summer thunderclouds. However, there may exit another condition such as clustering or self-organizing effect of thunderclouds for Sprite production.
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Observation of Sprites over the Sea of Japan and conditions for lightning-induced Sprites in winter
Asia-Pacific Conference on Environmental Electromagnetics 2003. CEEM 2003. Proceedings., 2003Co-Authors: Masashi Hayakawa, T. Nakamura, Y. Hobara, Earle WilliamsAbstract:Sprites are a newly discovered optical emission in the mesosphere over large thunderstorms. We have succeeded in observing Sprites for winter lightning in the Hokuriku area (Japan Sea side) of Japan in the winter of 2001/2002. The optical results on three days are compared with the corresponding characteristics of parent (causative) lightning with particular attention to the significant differences between Hokuriku winter lightning and the more widely studied continental lightning. Despite significant differences with Hokuriku winter lightning, we have found nearly the same Sprite properties as already observed in continental USA, with one significant difference (simpler shape for Hokuriku winter Sprite). We also discuss the criteria for Sprite occurrence. Specifically, two similar criteria are found: (1) cloud-to-ground discharges of positive polarity; (2) the presence of a certain threshold in vertical charge moment (200-300 C.km) (roughly consistent with that for continental USA). Mesoscale convective systems are not necessary to store the charge necessary for Sprites, but the parent Hokuriku winter clouds are substantially smaller than the minimum scale for Sprite occurrence in continental lightning, but they are larger in area than ordinary summer thunderclouds. However, there may exist another condition, such as clustering or the self-organizing effect of thunderclouds, for Sprite production.
