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Victor P Pasko - One of the best experts on this subject based on the ideXlab platform.
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dynamics of streamer to leader transition at reduced air densities and its implications for propagation of lightning leaders and gigantic jets
Journal of Geophysical Research, 2013Co-Authors: Caitano L Da Silva, Victor P PaskoAbstract:[1] In this paper we present modeling studies of air heating by electrical discharges in a wide range of pressures. The developed model is capable of quantifying the different contributions for heating of air at the particle level and rigorously accounts for the vibration-dissociation-vibration coupling. The model is validated by calculating the breakdown times of short air gaps and comparing to available experimental data. Detailed discussion on the role of electron detachment in the development of the thermal-ionizational instability that triggers the spark development in short air gaps is presented. The dynamics of fast heating by quenching of excited electronic states is discussed and the scaling of its main channels with ambient air density is quantified. The developed model is employed to study the streamer-to-leader transition process and to obtain its scaling with ambient air density. Streamer-to-leader transition is the name given to a sequence of events occurring in a thin plasma channel through which a relatively strong current is forced through, culminating in heating of ambient gas and increase of the electrical conductivity of the channel. This process occurs during the inception of leaders (from sharp metallic structures, from hydrometeors inside the Thundercloud, or in virgin air) and during their propagation (at the leader head or during the growth of a space leader). The development of a thermal-ionizational instability that culminates in the leader formation and propagation is characterized by a change in air ionization mechanism from electron impact to associative ionization and by contraction of the plasma channel. The introduced methodology for estimation of leader speeds shows that the propagation of a leader is limited by the air heating of every newly formed leader section. It is demonstrated that the streamer-to-leader transition time has an inverse-squared dependence on the ambient air density at near-ground pressures, in agreement with similarity laws for Joule heating in a streamer channel. Model results indicate that a deviation from this similarity scaling occurs at very low air densities, where the rate of electronic power deposition is balanced by the channel expansion, and air heating from quenching of excited electronic states is very inefficient. These findings place a limit on the maximum altitude at which a hot and highly conducting lightning leader channel can be formed in the Earth’s atmosphere, result which is important for understating of the gigantic jet (GJ) discharges between Thundercloud tops and the lower ionosphere. Simulations of leader speeds at GJ altitudes demonstrate that initial speeds of GJs are consistent with the leader propagation mechanism. The simulation of a GJ, escaping upward from a Thundercloud top, shows that the lengthening of the leader streamer zone, in a medium of exponentially decreasing air density, determines the existence of an altitude at which the streamer zones of GJs become so long that they dynamically extend (jump) all the way to the ionosphere.
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three dimensional fractal modeling of intracloud lightning discharge in a new mexico thunderstorm and comparison with lightning mapping observations
Journal of Geophysical Research, 2007Co-Authors: J A Riousset, Victor P Pasko, P R Krehbiel, R J Thomas, W RisonAbstract:[1] The direct comparison of lightning mapping observations by the New Mexico Tech Lightning Mapping Array (LMA) with realistic models of Thundercloud electrical structures and lightning discharges represents a useful tool for studies of electrification mechanisms in thunderstorms, initiation and propagation mechanisms of different types of lightning discharges as well as for understanding of electrical and energetic effects of tropospheric thunderstorms on the upper regions of the Earth's atmosphere. This paper presents the formulation of a new three-dimensional probabilistic model for investigating the structure and development of bidirectional positive and negative lightning leaders. The results closely resemble structures observed by the LMA during intracloud discharges. The model represents a synthesis of the original dielectric breakdown model based on fractal approach proposed by Niemeyer et al. (1984) and the equipotential lightning channel hypothesis advanced by Kasemir (1960) and places special emphasis on obtaining self-consistent solutions preserving complete charge neutrality of the discharge trees at any stage of the simulation. A representative simulation run is compared to a typical intracloud discharge measured by LMA in a New Mexico thunderstorm on 31 July 1999. Following the conclusions from Coleman et al. (2003), the comparison of the model and observed discharges reveals that an adequate choice of the electrical structure of the model Thundercloud permits the development of a model intracloud discharge reproducing principal features of the observed event including the initial vertical extension of the discharge between the main negative and upper positive charge regions of the Thundercloud, and the subsequent horizontal propagations in these regions. Also consistent with observations (e.g., Coleman et al., 2003), negative and positive leaders mainly develop in the upper positive and main negative charge regions, respectively. For the particular model case presented in this paper, the total charge transfer, the vertical dipole moment and the average linear charge density associated with the development of bidirectional structure of leader channels are estimated to be 37.5 C, 122 C·km, and 0.5 mC/m, respectively, in good agreement with related data reported in the refereed literature. The model results also demonstrate that the bulk charge carried by the integral action of positive and negative leaders leads to a significant (up to 80%) reduction of the electric field values inside the Thundercloud, significantly below the lightning initiation threshold.
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atmospheric physics electric jets
Nature, 2003Co-Authors: Victor P PaskoAbstract:Powerful electric currents have been detected in discharges between Thunderclouds and the upper atmosphere. Carried by gigantic jets, they are a new factor in the model of the Earth's electrical and chemical environment.
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electrical discharge from a Thundercloud top to the lower ionosphere
Nature, 2002Co-Authors: Victor P Pasko, U S Inan, M A Stanley, J D Mathews, T G WoodAbstract:For over a century, numerous undocumented reports have appeared about unusual large-scale luminous phenomena above Thunderclouds1,2,3,4,5,6 and, more than 80 years ago, it was suggested that an electrical discharge could bridge the gap between a Thundercloud and the upper atmosphere7,8. Since then, two classes of vertically extensive optical flashes above Thunderclouds have been identified—sprites9,10,11 and blue jets12,13,14. Sprites initiate near the base of the ionosphere, develop very rapidly downwards at speeds which can exceed 107 m s-1 (ref. 15), and assume many different geometrical forms16,17,18,19. In contrast, blue jets develop upwards from cloud tops at speeds of the order of 105 m s-1 and are characterized by a blue conical shape12,13,14. But no experimental data related to sprites or blue jets have been reported which conclusively indicate that they establish a direct path of electrical contact between a Thundercloud and the lower ionosphere. Here we report a video recording of a blue jet propagating upwards from a Thundercloud to an altitude of about 70 km, taken at the Arecibo Observatory, Puerto Rico. Above an altitude of 42 km—normally the upper limit for blue jets and the lower terminal altitude for sprites—the flash exhibited some features normally observed in sprites. As we observed this phenomenon above a relatively small thunderstorm cell, we speculate that it may be common and therefore represent an unaccounted for component of the global electric circuit.
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dynamic coupling of quasi electrostatic Thundercloud fields to the mesosphere and lower ionosphere sprites and jets
1996Co-Authors: Victor P PaskoAbstract:Red Sprites and Blue Jets are two different types of recently discovered optical flashes ob- served above large thunderstorm systems. Sprites are luminous glows occurring at altitudes typically ranging from approximately 50 to 90 km. In video they exhibit a red color at their top which gradually changes to blue at lower altitudes. Sprites may occur singly or in clusters of two or more. The lateral extent of "unit" sprites is typically 5-10 km and they endure for several milliseconds. Jets are upward moving (approximately 100 km/s) highly collimated beams of luminosity, emanating from the tops of Thunderclouds, extending up to approximately 50 km altitude and exhibiting a primarily blue color. We propose that sprites result from large electric field transients capable of causing electron heating, breakdown ionization and excitation of optical emissions at mesospheric altitudes following the removal of Thundercloud charge by a cloud-to-ground discharge. Depending on the history of charge accumulation and removal, and the distribution of ambient atmospheric conductivity, the breakdown region may have the shape of vertically oriented ionization column(s). Results of a two-dimensional and self consistent quasi-electrostatic (QE) model indicate that most of the observed features of sprites can be explained in terms of the formation and self-driven propagation of streamer type channels of breakdown ionization. Comparison of the optical emission intensities of the 1st and 2nd positive bands of N2, Meinel and 1st negative bands of N2(+) and the 1st negative band of O2(+) demonstrates that the 1st positive band of N2 is the dominant optical emission in the altitude range approximately 50-90 km, which accounts for the observed red color of sprites. Optical emissions of the 1st and 2nd positive bands of N2 occur in carrot-like vertical structures with typical transverse dimension approximately 5-10 km which can span an altitude range from approximately 80 km to well below approximately 50 km. The appearance of optical emissions associated with sprites can be delayed in time (approximately 1-20 ms) with respect to the causative cloud to ground discharge. Theoretical model results are found to be in good agreement with recent video, photometric and spectral measurements of sprites.
Hamid K. Rassoul - One of the best experts on this subject based on the ideXlab platform.
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Thunderstorm charge structures producing gigantic jets
Nature Publishing Group, 2018Co-Authors: Levi D. Boggs, Ningyu Liu, Jeremy A. Riousset, Feng Shi, Steven Lazarus, Michael Splitt, Hamid K. RassoulAbstract:Abstract Gigantic jets are atmospheric electrical discharges that propagate from the top of Thunderclouds to the lower ionosphere. They begin as lightning leaders inside the Thundercloud, and the Thundercloud charge structure primarily determines if the leader is able to escape upward and form a gigantic jet. No observationally verified studies have been reported on the Thundercloud charge structures of the parent storms of gigantic jets. Here we present meteorological observations and lightning simulation results to identify a probable Thundercloud charge structure of those storms. The charge structure features a narrow upper charge region that forms near the end of an intense convective pulse. The convective pulse produces strong storm top divergence and turbulence, as indicated by large values of storm top radial velocity differentials and spectrum width. The simulations show the charge structure produces leader trees closely matching observations. This charge structure may occur at brief intervals during a thunderstorm’s evolution due to the brief nature of convective pulses, which may explain the rarity of gigantic jets compared to other forms of atmospheric electrical discharges
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Upward electrical discharges observed above Tropical Depression Dorian
2016Co-Authors: Ningyu Liu, Joseph R. Dwyer, Hamid K. Rassoul, Nicholas Spiva, Dwayne Free, Steven A. CummerAbstract:Observation of upward electrical discharges from thunderstorms has been sporadically reported in the scientific literature. According to their terminal altitudes, they are classified as starters (20–30 km), jets (40–50 km) and gigantic jets (70–90 km). They not only have a significant impact on the occupied atmospheric volumes but also electrically couple different atmospheric regions. However, as they are rare and unpredictable, our knowledge of them has been built on observations that typically record only one type of such discharges. Here we report a close-distance observation of seven upward discharges including one starter, two jets and four gigantic jets above Tropical Depression Dorian. Our optical and electromagnetic data indicate that all events are of negative polarity, suggesting they are initiated in the same Thundercloud charge region. The data also indicate that the lightning-like discharge channel can extend above Thunderclouds by about 30 km, but the discharge does not emit low-frequency electromagnetic radiation as normal lightning
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streamer formation and branching from model hydrometeors in subbreakdown conditions inside Thunderclouds
Journal of Geophysical Research, 2015Co-Authors: Samaneh Sadighi, Ningyu Liu, J R Dwyer, Hamid K. RassoulAbstract:Electric field values measured inside Thunderclouds have consistently been reported to be up to an order of magnitude lower than the value required for the conventional electrical breakdown of air. This result has made it difficult to explain how lightning frequently occurs in Thunderclouds. A few different theories have been offered to explain the lightning initiation process, one of them being the theory of lightning initiation from hydrometeors. According to this theory, lightning can be initiated from electrical discharges originating around Thundercloud water or ice particles in the measured Thundercloud electric field. These particles, called hydrometeors, are believed to cause significant enhancement of the Thundercloud electric field in their vicinity and then initiate streamers that are the precursor discharges for the hot lightning leader channel. Previously, Liu et al. (2012a) reported streamer formation from a model hydrometeor in an electric field value of half of the conventional breakdown threshold (Ek) for air. In this paper, we present modeling results for streamer formation in electric fields as low as one third of the breakdown threshold. According to our results, initiation of stable streamers from Thundercloud hydrometeors in a 0.3Ek electric field is possible, only if enhanced ambient ionization levels (e.g., the ionization created by corona discharges around the same or other nearby hydrometeors) are present ahead of the streamer. The magnitude and distribution of this ambient density may be a determining factor on whether the streamer branches, recovers after the prebranching stage, or continues propagating stably. We investigate the streamer branching behavior and characteristics and test a theory that has recently been proposed to explain this phenomenon. We find that the geometry of the streamer head plays an important role in the streamer branching phenomena. The fast radial movement of the maximum streamer head curvature, combined with the slow reduction of the maximum curvature value, eventually leads the streamer head to branching. Finally, we compare our modeling results with laboratory experiments and realistic Thundercloud conditions and discuss the implications of this study to lightning initiation and other lightning-related phenomena.
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Effects of pressure and humidity on positive corona inception from Thundercloud hydrometeors
Journal of Atmospheric and Solar-Terrestrial Physics, 2012Co-Authors: Ningyu Liu, Joseph R. Dwyer, Hamid K. RassoulAbstract:This paper reports a study on the inception condition of positive corona discharges around Thundercloud hydrometeors that are simulated as a spherical point electrode. The corona inception from the hydrometeor is investigated using a model developed by Naidis (2005), which suggests that the discharge becomes self-sustaining when the number of ionizing photons produced by all secondary electron avalanches is equal to that by a primary avalanche. For an isolated, charged hydrometeor in dry air of varying pressure, the results show that the onset of positive corona discharges from a large hydrometeor at high pressure requires a stronger avalanche multiplication than those from a small hydrometeor at low pressure. The onset voltage and surface electric field are obtained for Thundercloud hydrometeors of different radii. For a hydrometeor of a radius of 1 mm at atmospheric pressure, the onset surface field reaches about 2.75 times the conventional breakdown threshold field. In humid air (a gas mixture of dry air and water vapor), it is found that a stronger avalanche is required for the corona onset, and the effect of humidity is more pronounced for large hydrometeors. The absorption of the ionizing photons by water vapor is the main reason why a stronger avalanche is required for the corona inception in humid air. As corona discharges from an isolated hydrometeor remove the charge on it, this discharging mechanism sets an upper limit on hydrometeor charge that agrees reasonably with the reported observations of maximum precipitation charge. Finally, we discuss the corona inception condition from a charged hydrometeor in non-zero ambient field of Thundercloud condition.
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estimation of the fluence of high energy electron bursts produced by Thunderclouds and the resulting radiation doses received in aircraft
Journal of Geophysical Research, 2010Co-Authors: J R Dwyer, D M Smith, M A Uman, Z Saleh, Brian W Grefenstette, B J Hazelton, Hamid K. RassoulAbstract:[1] Using recent X-ray and gamma-ray observations of terrestrial gamma-ray flashes (TGFs) from spacecraft and of natural and rocket-triggered lightning from the ground, along with detailed models of energetic particle transport, we calculate the fluence (integrated flux) of high-energy (million electronvolt) electrons, X rays, and gamma rays likely to be produced inside or near Thunderclouds in high electric field regions. We find that the X-ray/gamma-ray fluence predicted for lightning leaders propagating inside Thunderclouds agrees well with the fluence calculated for TGFs, suggesting a possible link between these two phenomena. Furthermore, based on reasonable meteorological assumptions about the magnitude and extent of the electric fields, we estimate that the fluence of high-energy runaway electrons can reach biologically significant levels at aircraft altitudes. If an aircraft happened to be in or near the high-field region when either a lightning discharge or a TGF event is occurring, then the radiation dose received by passengers and crew members inside that aircraft could potentially approach 0.1 Sv (10 rem) in less than 1 ms. Considering that commercial aircraft are struck by lightning, on average, one to two times per year, the risk of such large radiation doses should be investigated further.
N L Aleksandrov - One of the best experts on this subject based on the ideXlab platform.
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non stationary corona around multi point system in atmospheric electric field i onset electric field and discharge current
Journal of Atmospheric and Solar-Terrestrial Physics, 2014Co-Authors: E M Bazelyan, Yu P Raizer, N L AleksandrovAbstract:Abstract The properties of a non-stationary glow corona maintained near the tips of a multi-point ground system in a time-varying Thundercloud electric field have been studied numerically and analytically. Computer and analytical models were developed to simulate the corona discharge initiated from a system of identical vertical conductive electrodes distributed uniformly over a grounded plane surface. The simulation was based on a solution of the electrostatic equation for electric field and continuity equations for light and aerosol ions. The development of individual corona space charge layers from different points and the formation of a united plane layer were considered. The effect of system dimensions and that of the distance between electrodes on the external electric field corresponding to corona onset near the rod tips was investigated. The evolution in time of the corona current was calculated for systems with various numbers of coronating rods in time-varying atmospheric electric field. In the limit of infinite number of coronating rods, reasonable agreement was obtained between numerical calculations and analytical theory considering the effect of surrounding rods on the corona discharge from a given rod in a simplified integral way. Conditions were determined under which the corona properties of a multi-point system are similar to the properties of a plane surface emitting ions into the atmosphere. In this case, the corona current density is governed by the time derivative of the Thundercloud electric field and is independent of the ion mobility and of the coronating system dimensions. The total corona space charge injected into the atmosphere per unit area by a given instant is controlled by the Thundercloud electric field at this instant and depends on the geometrical parameters of the system only indirectly, through the corona onset atmospheric electric field. This simple model could be used to simulate a corona discharge during thunderstorms at the earth’s surface covered with dense vegetation. In particular, according to the model of an emitting plane, the current densities in the range 1–10 nA/m 2 are expected when the Thundercloud electric field increases by ∼50 kV/m over time interval in the range 30–300 s, in qualitative agreement with the analysis of available field observations.
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corona processes and lightning attachment the effect of wind during thunderstorms
Atmospheric Research, 2009Co-Authors: E M Bazelyan, Yu P Raizer, N L Aleksandrov, F DalessandroAbstract:A simple model of a glow corona occurring near the tip of a grounded electrode in a Thundercloud electric field that can be enhanced by an approaching downward leader has been studied analytically and numerically with regard to the effect of wind. We obtained an approximate expression for corona current taking into account the (i) removal of space charge from the coronating point due to ion drift and wind and (ii) image of the charge in the ground. As the wind velocity decreases to zero, the expression tends to that obtained previously in the absence of wind. It was shown analytically and numerically that, in a Thundercloud electric field, even moderate wind velocities lead to hundreds of percent increase in the corona current. This current decreases with time only slightly in a steady Thundercloud electric field, as opposed to the current behavior in the absence of wind. However, even strong wind is not sufficient to affect the properties of a corona intensified in the electric field of an approaching downward leader. The occurrence of wind does not affect the conditions for initiation of an upward connecting leader from grounded objects and consequently the efficiency of lightning rods of ordinary height.
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corona initiated from grounded objects under thunderstorm conditions and its influence on lightning attachment
Plasma Sources Science and Technology, 2008Co-Authors: E M Bazelyan, Yu P Raizer, N L AleksandrovAbstract:Lightning attachment to grounded structures due to the initiation of an upward connecting leader from them is considered taking into account the effect of corona space charge near the structures. It is shown that the corona space charge strongly affects the initiation and development of the connecting leader. Specific features of a non-stationary corona are analysed analytically and numerically for one-dimensional electrode geometries and for a grounded rod coronating in a slowly varying Thundercloud electric field that can be enhanced by the charge of an approaching downward lightning leader. Initiation and development of an upward connecting leader or upward lightning from high ground objects are investigated. Prospects of using the effect of coronae to control downward lightning discharges are discussed.
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corona discharge at the tip of a tall object in the electric field of a Thundercloud
Plasma Physics Reports, 2002Co-Authors: N L Aleksandrov, E M Bazelyan, R B Carpenter, M M Drabkin, Yu P RaizerAbstract:Characteristics of a positive transient corona discharge near the tip of a tall solitary grounded object in the electric field of a Thundercloud are studied analytically and numerically. The time evolution of the discharge current and the space distribution of the total electric field are simulated for different growth rates of the external field and the dimensions and geometry of the stressed electrode. The effect of aerosol ions is shown to be negligible at a short duration of the corona. The developed simplified analytical approach agrees with numerical simulations.
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the effect of coronae on leader initiation and development under thunderstorm conditions and in long air gaps
Journal of Physics D, 2001Co-Authors: N L Aleksandrov, E M Bazelyan, R B Carpenter, M M Drabkin, Yu P RaizerAbstract:The initiation and development of a leader is theoretically studied by considering an electrode which is embedded in a cloud of space charge injected by a corona discharge. The focus is on the initiation of upward lightning from a stationary grounded object in a Thundercloud electric field. The main results are also applicable to the leader process in long laboratory air gaps at direct voltage. Simple physical models of non-stationary coronae developing in free space near a solitary stressed sphere and of a leader propagating in the space charge cloud of coronae are suggested. It is shown that the electric field redistribution due to the space charge released by the long corona discharge near the top of a high object hinders the initiation and development of an upward leader from the object in a Thundercloud electric field. The conditions for the formation of corona streamers that are required to initiate a leader are derived. The criteria are obtained for a leader to be initiated and propagate in the space charge cloud. A hypothesis is proposed that the streamers are never initiated near the top of a high object under thunderstorm conditions if at ground level there is only a slowly-varying electric field of the Thundercloud. The streamers may be induced by the fast-rising electric field of distant downward leaders or intracloud discharges.
A Chilingarian - One of the best experts on this subject based on the ideXlab platform.
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structures of the intracloud electric field supporting origin of long lasting thunderstorm ground enhancements
Physical Review D, 2018Co-Authors: A Chilingarian, G Hovsepyan, S Soghomonyan, M Zazyan, M ZelenyyAbstract:The problem of Thundercloud electrification is one of the most difficult ones in atmospheric physics. The structure of electric fields in clouds escapes from the detailed in situ measurements; few balloon flights reveal these rather complicated structures. To gain insight into the problem of the charge structure of a Thundercloud, we use new key evidence---the fluxes of particles from a Thundercloud, the so-called thunderstorm ground enhancements---TGEs. TGEs originate from electron acceleration and multiplication processes in the strong electric fields in the Thundercloud, and the intensity and energy spectra of electrons and gamma rays as observed on the Earth's surface are directly connected with the atmospheric electric field. Discovery of long-lasing TGEs poses new challenges for revealing structures in the Thundercloud responsible for hours-extending gamma ray fluxes. In the presented paper, we demonstrate that experimentally measured intensities and energy spectra of the ``Thundercloud particles'' give clues for understanding charge structures embedded in the atmosphere. A rather short ``runaway'' process above the detector site, which is consistent with the tripole structure of the cloud electrification, is changing to a much less energetic emission that lasts for hours. Measurements of enhanced particle fluxes are accompanied by the simulation experiments with corsika and geant4 codes.
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role of the lower positive charge region lpcr in initiation of the thunderstorm ground enhancements tges
Physical Review D, 2012Co-Authors: A Chilingarian, H MkrtchyanAbstract:Despite the ubiquity of thunderstorms, lightning, and related electrical phenomena, many important electromagnetic processes in our atmosphere are poorly understood; the key questions about the Thundercloud electrification and lightning initiation remain unanswered. The bulk information on particle fluxes correlated with thunderstorm can be used to better understand the electrical structure of Thunderclouds. Only very specific electric configuration of the lower part of the cloud can support the sustainable acceleration of the electrons. Our analysis is based on the thunderstorm data from the Aragats Mountain in Armenia, 3200 m above sea level Varieties of particle detectors located at Aragats Space Environmental Center are registering neutral and charged particle fluxes correlated with thunderstorms, so-called Thunderstorm Ground Enhancements (TGEs). Simultaneously the electrical mills and lightning detectors are monitoring the near-surface electric field and type of lightning occurrences; weather stations are measuring plenty of meteorological parameters. In the present paper we relate particle fluxes to the electrical structure of Thunderclouds, namely, to the origination of the Lower Positive Charged Region (LPCR) below the main negative charged layer in the middle of the Thundercloud, and to lightning occurrences. Only after creation of the lower dipole in the Thundercloud can the electrons be accelerated and particle flux be directed downward. Maturity of the LPCR is correlated with increasing particle fluxes. Thus, the temporal evolution of TGE gives direct evidence of the maturity of LPCR, its initiation, and its decaying.
H Tsuchiya - One of the best experts on this subject based on the ideXlab platform.
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Thundercloud project exploring high energy phenomena in Thundercloud and lightning
arXiv: Atmospheric and Oceanic Physics, 2020Co-Authors: Takayuki Yuasa, Yuuki Wada, T Enoto, Yoshihiro Furuta, H Tsuchiya, Shohei Hisadomi, Yuna Tsuji, Kazufumi Okuda, Takahiro Matsumoto, Kazuhiro NakazawaAbstract:We designed, developed, and deployed a distributed sensor network aiming at observing high-energy ionizing radiation, primarily gamma rays, from winter Thunderclouds and lightning in coastal areas of Japan. Starting in 2015, we have installed, in total, more than 15 units of ground-based detector system in Ishikawa Prefecture and Niigata Prefecture, and accumulated 551 days of observation time in four winter seasons from late 2015 to early 2019. In this period, our system recorded 51 gamma-ray radiation events from Thundercloud and lightning. Highlights of science results obtained from this unprecedented amount of data include the discovery of photonuclear reaction in lightning which produces neutrons and positrons along with gamma rays, and deeper insights into the life cycle of a particle-acceleration and gamma-ray-emitting region in a Thundercloud. The present paper reviews objective, methodology, and results of our experiment, with a stress on its instrumentation.
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on ground detection of an electron positron annihilation line from Thunderclouds
Physical Review E, 2016Co-Authors: D Umemoto, Takayuki Yuasa, H Tsuchiya, Teruaki Enoto, Shinya Yamada, M Kawaharada, Takao Kitaguchi, K Nakazawa, M Kokubun, H KatoAbstract:Thunderclouds can produce bremsstrahlung gamma-ray emission, and sometimes even positrons. At 00:27:00 (UT) on 13 January 2012, an intense burst of gamma rays from a Thundercloud was detected by the GROWTH experiment, located in Japan, facing the Sea of Japan. The event started with a sharp gamma-ray flash with a duration of <300 ms coincident with an intracloud discharge, followed by a decaying longer gamma-ray emission lasting for ∼60 s. The spectrum of this prolonged emission reached ∼10 MeV, and contained a distinct line emission at 508±3(stat.)±5(sys.) keV, to be identified with an electron-positron annihilation line. The line was narrow within the instrumental energy resolution (∼80keV), and contained 520±50 photons which amounted to ∼10% of the total signal photons of 5340±190 detected over 0.1-10 MeV. As a result, the line equivalent width reached 280±40 keV, which implies a nontrivial result. The result suggests that a downward positron beam produced both the continuum and the line photons.
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observation of Thundercloud related gamma rays and neutrons in tibet
Physical Review D, 2012Co-Authors: H Tsuchiya, K Hibino, K Kawata, N Hotta, N Tateyama, M Ohnishi, M Takita, Dianyong Chen, J Huang, M MiyasakaAbstract:During the 2010 rainy season in Yangbajing (4300 m above sea level) in Tibet, China, a long-duration count enhancement associated with Thunderclouds was detected by a solar-neutron telescope and neutron monitors installed at the Yangbajing Comic Ray Observatory. The event, lasting for similar to 40 min, was observed on July 22, 2010. The solar-neutron telescope detected significant gamma-ray signals with energies >40 MeV in the event. Such a prolonged high-energy event has never been observed in association with Thunderclouds, clearly suggesting that electron acceleration lasts for 40 min in Thunderclouds. In addition, Monte Carlo simulations showed that >10 MeV gamma rays largely contribute to the neutron monitor signals, while >1 keV neutrons produced via a photonuclear reaction contribute relatively less to the signals. This result suggests that enhancements of neutron monitors during thunderstorms are not necessarily clear evidence for neutron production, as previously thought.
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detection of high energy gamma rays from winter Thunderclouds
Physical Review Letters, 2007Co-Authors: H Tsuchiya, Takayuki Yuasa, T Enoto, Takao Kitaguchi, M Kokubun, S Yamada, Madoka Kawaharada, Hiroshi Kato, M Okano, S NakamuraAbstract:: A report is made on a comprehensive observation of a burstlike gamma-ray emission from Thunderclouds on the Sea of Japan, during strong thunderstorms on 6 January 2007. The detected emission, lasting for approximately 40 sec, preceded cloud-to-ground lightning discharges. The burst spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung photons originating from relativistic electrons. This ground-based observation provides the first clear evidence that strong electric fields in Thunderclouds can continuously accelerate electrons beyond 10 MeV prior to lightning discharges.