Journal of Geophysical Research Atmospheres, volume 125, issue 23

Observations of the Origin of Downward Terrestrial Gamma‐Ray Flashes

J. W. Belz 1
, 
Paul R. Krehbiel 2
, 
J. REMINGTON 1
, 
MARK STANLEY 2
, 
R. U. Abbasi 3
, 
R Levon 1
, 
W Rison 2
, 
D. Rodeheffer 2
, 
T. Abu-Zayyad 1
, 
M. ALLEN 1
, 
E. BARCIKOWSKI 1
, 
D. R. Bergman 1
, 
S. A. BLAKE 1
, 
M. Byrne 1
, 
R. CADY 1
, 
B. G. CHEON 4
, 
M. CHIKAWA 5
, 
A. DI MATTEO 6, 7
, 
T. Fujii 8
, 
K. Fujita 9
, 
R. FUJIWARA 9
, 
M. FUkUSHIMA 10, 11
, 
G. FURLICH 1
, 
W. HANLON 1
, 
M. Hayashi 12
, 
Y. Hayashi 9
, 
N. HAYASHIDA 13
, 
K. Hibino 13
, 
K. HONDA 14
, 
D. IKEDA 14
, 
T. Inadomi 15
, 
N. INOUE 16
, 
T. Ishii 14
, 
H. Ito 17
, 
D. Ivanov 1
, 
H. Iwakura 15
, 
H. M. Jeong 18
, 
S. Jeong 18
, 
C. C. H. Jui 1
, 
K. KADOTA 19
, 
F. KAKIMOTO 20
, 
O. Kalashev 21
, 
K. KASAHARA 22
, 
S. Kasami 23
, 
H. Kawai 24
, 
S. Kawakami 9
, 
K. Kawata 10
, 
E. Kido 10
, 
H. B. Kim 4
, 
J H Kim 1
, 
J H Kim 9
, 
V. KUZMIN 21
, 
M. K. Kuznetsov 6, 21
, 
M. Kuznetsov 6, 21
, 
Y. J. Kwon 25
, 
K H Lee 18
, 
B. LUBSANDORZHIEV 21
, 
J. P. LUNDQUIST 1
, 
K Machida 14
, 
H. Matsumiya 9
, 
J. N. MATTHEWS 1
, 
T Matuyama 9
, 
R. MAYTA 9
, 
M. MINAMINO 9
, 
K. Mukai 14
, 
I. MYERS 1
, 
S. Nagataki 17
, 
K. Nakai 9
, 
R. Nakamura 15
, 
T. Nakamura 26
, 
Y. Nakamura 15
, 
Y Nakamura 15
, 
T. NONAKA 10
, 
H. Oda 9
, 
S. Ogio 9, 27
, 
M. OHNISHI 10
, 
H. OHOKA 10
, 
Y. Oku 23
, 
T. Okuda 28
, 
Y. Omura 9
, 
Masaomi Ono 17
, 
M. Ono 17
, 
A. OSHIMA 29
, 
S. OZAWA 22
, 
I. H. PARK 18
, 
M Potts 1
, 
M. S. PSHIRKOV 21, 30
, 
D. C. RODRIGUEZ 1
, 
G. Rubtsov 21
, 
D. RYU 31
, 
H. Sagawa 10
, 
R. SAHARA 9
, 
K. SAITO 10
, 
Y. Saito 15
, 
N. SAKAKI 10
, 
T. SAKO 10
, 
N. SAKURAI 9
, 
Kei Sano 15
, 
K. Sano 15
, 
T. Seki 15
, 
K. SEKINO 9
, 
F. SHIBATA 14
, 
T Shibata 10
, 
H. SHIMODAIRA 10
, 
B. K. SHIN 9
, 
H. S. Shin 10
, 
J. D. Smith 1
, 
Pierre Sokolsky 1
, 
P. Sokolsky 1
, 
N. Sone 15
, 
B. T. Stokes 1
, 
T. A. STROMAN 1
, 
Y. Takagi 9
, 
Y. TAKAHASHI 9
, 
M. Takeda 10
, 
R. TAKEISHI 18
, 
A. TAKETA 32
, 
M. TAKITA 10
, 
Y. Tameda 23
, 
K Tanaka 33
, 
Masayuki Tanaka 34
, 
Y. TANOUE 9
, 
S. B. Thomas 1
, 
G. B. THOMSON 1
, 
P. TINYAKOV 6, 21
, 
I. Tkachev 21
, 
H. Tokuno 20
, 
T. TOMIDA 15
, 
S. Troitsky 21
, 
Y. TSUNESADA 9, 27
, 
Y. UCHIHORI 35
, 
S. UDO 13
, 
T. Uehama 15
, 
F. URBAN 36
, 
M Wallace 1
, 
T. Wong 1
, 
M. Yamamoto 15
, 
H. Yamaoka 34
, 
K. Yamazaki 29
, 
K. Yashiro 37
, 
M. Yosei 23
, 
H. YOSHII 38
, 
Y. ZHEZHER 10, 21
, 
Z. ZUNDEL 1
Show full list: 144 authors
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Institute of Physics, Czech Academy of Sciences CEICO Prague Czech Republic | 
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Publication type: Journal Article
Publication date: 2020-10-05
scimago Q1
SJR: 1.710
CiteScore: 7.3
Impact factor: 3.8
ISSN: 2169897X, 21698996
Space and Planetary Science
Earth and Planetary Sciences (miscellaneous)
Atmospheric Science
Geophysics
Abstract
In this paper we report the first close, high-resolution observations of downward-directed terrestrial gamma-ray flashes (TGFs) detected by the large-area Telescope Array cosmic ray observatory, obtained in conjunction with broadband VHF interferometer and fast electric field change measurements of the parent discharge. The results show that the TGFs occur during strong initial breakdown pulses (IBPs) in the first few milliseconds of negative cloud-to-ground and low-altitude intracloud flashes, and that the IBPs are produced by a newly-identified streamer-based discharge process called fast negative breakdown. The observations indicate the relativistic runaway electron avalanches (RREAs) responsible for producing the TGFs are initiated by embedded spark-like transient conducting events (TCEs) within the fast streamer system, and potentially also by individual fast streamers themselves. The TCEs are inferred to be the cause of impulsive sub-pulses that are characteristic features of classic IBP sferics. Additional development of the avalanches would be facilitated by the enhanced electric field ahead of the advancing front of the fast negative breakdown. In addition to showing the nature of IBPs and their enigmatic sub-pulses, the observations also provide a possible explanation for the unsolved question of how the streamer to leader transition occurs during the initial negative breakdown, namely as a result of strong currents flowing in the final stage of successive IBPs, extending backward through both the IBP itself and the negative streamer breakdown preceding the IBP.
Found 69
By date By citations
IOP Publishing
The physics of streamer discharge phenomena
Nijdam S., Teunissen J., Ebert U.
Plasma Sources Science and Technology scimago Q1 wos Q1 , 
2020-11-02,  citations by CoLab: 296 ,  Abstract  
In this review we describe a transient type of gas discharge which is commonly called a streamer discharge, as well as a few related phenomena in pulsed discharges. Streamers are propagating ionization fronts with self-organized field enhancement at their tips that can appear in gases at (or close to) atmospheric pressure. They are the precursors of other discharges like sparks and lightning, but they also occur in for example corona reactors or plasma jets which are used for a variety of plasma chemical purposes. When enough space is available, streamers can also form at much lower pressures, like in the case of sprite discharges high up in the atmosphere. We explain the structure and basic underlying physics of streamer discharges, and how they scale with gas density. We discuss the chemistry and applications of streamers, and describe their two main stages in detail: inception and propagation. We also look at some other topics, like interaction with flow and heat, related pulsed discharges, and electron runaway and high energy radiation. Finally, we discuss streamer simulations and diagnostics in quite some detail. This review is written with two purposes in mind: First, we describe recent results on the physics of streamer discharges, with a focus on the work performed in our groups. We also describe recent developments in diagnostics and simulations of streamers. Second, we provide background information on the above-mentioned aspects of streamers. This review can therefore be used as a tutorial by researchers starting to work in the field of streamer physics.
American Geophysical Union
Radio Interferometer Observations of an Energetic in‐Cloud Pulse Reveal Large Currents Generated by Relativistic Discharges
Tilles J.N., Krehbiel P.R., Stanley M.A., Rison W., Liu N., Lyu F., Cummer S.A., Dwyer J.R., Senay S., Edens H., Fan X., Brown R.G., Wilson J.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2020-09-22,  citations by CoLab: 30 ,  Abstract  
The production mechanism for terrestrial gamma ray flashes (TGFs) is not entirely understood, and details of the corresponding lightning activity and thunderstorm charge structure have yet to be fully characterized. Here we examine sub-microsecond VHF (14–88 MHz) radio interferometer observations of a 247-kA peak-current EIP, or energetic in-cloud pulse, a reliable radio signature of a subset of TGFs. The EIP consisted of three high-amplitude sferic pulses lasting ≃60 μs in total, which peaked during the second (main) pulse. The EIP occurred during a normal-polarity intracloud lightning flash that was highly unusual, in that the initial upward negative leader was particularly fast propagating and discharged a highly concentrated region of upper-positive storm charge. The flash was initiated by a high-power (46 kW) narrow bipolar event (NBE), and the EIP occurred about 3 ms later after ≃3 km upward flash development. The EIP was preceded ≃200 μs by a fast 6 × 106 m/s upward negative breakdown and immediately preceded and accompanied by repeated sequences of fast (107–108 m/s) downward then upward streamer events each lasting 10 to 20 μs, which repeatedly discharged a large volume of positive charge. Although the repeated streamer sequences appeared to be a characteristic feature of the EIP and were presumably involved in initiating it, the EIP sferic evolved independently of VHF-producing activity, supporting the idea that the sferic was produced by relativistic discharge currents. Moreover, the relativistic currents during the main sferic pulse initiated a strong NBE-like event comparable in VHF power (115 kW) to the highest-power NBEs.
Wiley
Indirectly Measured Ambient Electric Fields for Lightning Initiation in Fast Breakdown Regions
Cummer S.A.
Geophysical Research Letters scimago Q1 wos Q1 Open Access , 
2020-02-07,  citations by CoLab: 10 ,  Abstract  
We report a new approach to measure indirectly the ambient thunderstorm electric fields in fast positive breakdown regions. For a given geometry of the discharged fast breakdown region, we show that there is a minimum ambient electric field required to produce a given charge moment change. We apply this approach to the fast breakdown measurements for two events reported by Rison et al. (2016, https://doi.org/10.1038/ncomms10721) and find that the average ambient electric field in the discharged region is at least V/m at the 9.5 km initiation altitude of these events. This electric field is close to the runaway electron avalanche electric field and to the critical field for positive streamer propagation. These measurements provide a meaningful starting point for more detailed analyses or simulations of what occurs inside the fast breakdown process that is responsible for the initiation of at least some lightning discharges.
American Geophysical Union
First 10 Months of TGF Observations by ASIM
Østgaard N., Neubert T., Reglero V., Ullaland K., Yang S., Genov G., Marisaldi M., Mezentsev A., Kochkin P., Lehtinen N., Sarria D., Qureshi B.H., Solberg A., Maiorana C., Albrechtsen K., et. al.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2019-12-10,  citations by CoLab: 63 , 
American Geophysical Union
Temporal and Spatial Characteristics of Preliminary Breakdown Pulses in Intracloud Lightning Flashes
Shi D., Wang D., Wu T., Takagi N.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2019-11-06,  citations by CoLab: 15 ,  Abstract  
We have studied the temporal and spatial characteristics of preliminary breakdown (PB) pulses in 32 normal intracloud flashes recorded by a fast antenna lightning mapping array system called Fast Antenna Lightning Mapping Array. It was found that PB processes started with a stage of preliminary isolated pulses (PIPs) and followed by classic PB pulse (PBP) clusters. A typical PIP stage consists of two or three PIPs and on average lasts about 129 μs. A typical PBP cluster consists of several narrow pulses (NPs) and one classic PBP and on average lasts about 193 μs. During one PIP stage, the pulses occurring later usually have a lower altitude, indicating a kind of backward extension relative to the overall upward progression of PB process. On average, the horizontal and vertical extensions involved in a PIP stage are 60 and 216 m, respectively. In each PBP cluster, PBP is always located at the lowest height and behind its preceding NPs, while these NP locations could have various patterns in term of extension. On average, the overall horizontal and vertical extensions involved in a typical PBP cluster are 161 and 515 m, respectively. For both the PIP stage and PBP cluster, their vertical extensions are apparently longer than their horizontal extensions, reflecting a predominantly vertical channel of PB process. Based on the temporal and spatial characteristics of PB pulses, we have proposed a model to interpret how the PIPs, NPs, and PBPs are produced.
American Geophysical Union
The Plasma Nature of Lightning Channels and the Resulting Nonlinear Resistance
da Silva C.L., Sonnenfeld R.G., Edens H.E., Krehbiel P.R., Quick M.G., Koshak W.J.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2019-08-05,  citations by CoLab: 29 , 
American Geophysical Union
Analysis of Individual Terrestrial Gamma‐Ray Flashes With Lightning Leader Models and Fermi Gamma‐Ray Burst Monitor Data
Mailyan B.G., Xu W., Celestin S., Briggs M.S., Dwyer J.R., Cramer E.S., Roberts O.J., Stanbro M.
Journal of Geophysical Research Space Physics scimago Q1 wos Q2 , 
2019-08-01,  citations by CoLab: 24 , 
American Geophysical Union
Griffiths and Phelps Lightning Initiation Model, Revisited
Attanasio A., Krehbiel P.R., Silva C.L.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2019-07-15,  citations by CoLab: 23 , 
Springer Nature
Gamma-ray glow preceding downward terrestrial gamma-ray flash
Wada Y., Enoto T., Nakamura Y., Furuta Y., Yuasa T., Nakazawa K., Morimoto T., Sato M., Matsumoto T., Yonetoku D., Sawano T., Sakai H., Kamogawa M., Ushio T., Makishima K., et. al.
Communications Physics scimago Q1 wos Q1 Open Access , 
2019-06-25,  citations by CoLab: 60 ,  PDF,  Abstract  
Two types of high-energy events have been detected from thunderstorms. One is “terrestrial gamma-ray flashes” (TGFs), sub-millisecond emissions coinciding with lightning discharges. The other is minute-lasting “gamma-ray glows”. Although both phenomena are thought to originate from relativistic runaway electron avalanches in strong electric fields, the connection between them is not well understood. Here we report unequivocal simultaneous detection of a gamma-ray glow termination and a downward TGF, observed from the ground. During a winter thunderstorm in Japan on 9 January 2018, our detectors caught a gamma-ray glow, which moved for ~100 s with ambient wind, and then abruptly ceased with a lightning discharge. Simultaneously, the detectors observed photonuclear reactions triggered by a downward TGF, whose radio pulse was located within ~1 km from where the glow ceased. It is suggested that the highly-electrified region producing the glow was related to the initiation of the downward TGF. Thunderstorms are thought to produce two types of high-energy emissions, terrestrial gamma-ray flashes and gamma-ray glows however due to the difficulty in their observation the exact relation between the two is still not well-understood. Here, the authors report the simultaneous detection of a gamma-ray glow and a downward terrestrial gamma-ray flash suggesting the origin of the two phenomena are related.
Wiley
Low Frequency Radio Pulses Produced by Terrestrial Gamma‐Ray Flashes
Pu Y., Cummer S.A., Lyu F., Briggs M., Mailyan B., Stanbro M., Roberts O.
Geophysical Research Letters scimago Q1 wos Q1 Open Access , 
2019-06-06,  citations by CoLab: 33 , 
Springer Nature
Fast negative breakdown in thunderstorms
Tilles J.N., Liu N., Stanley M.A., Krehbiel P.R., Rison W., Stock M.G., Dwyer J.R., Brown R., Wilson J.
Nature Communications scimago Q1 wos Q1 Open Access , 
2019-04-09,  citations by CoLab: 82 ,  PDF,  Abstract  
Thunderstorms are natural laboratories for studying electrical discharges in air, where the vast temporal, spatial, and energy scales available can spawn surprising phenomena that reveal deficiencies in our understanding of dielectric breakdown. Recent discoveries, such as sprites, jets, terrestrial gamma ray flashes, and fast positive breakdown, highlight the diversity of complex phenomena that thunderstorms can produce, and point to the possibility for electrical breakdown/discharge mechanisms beyond dielectric breakdown theory based mainly on laboratory experiments. Here we present one such confounding discovery, termed fast negative breakdown, that does not fit with our current understanding of dielectric breakdown. Our adaptation of radio astronomy imaging techniques to study extremely transient lightning-associated events confirms that electrical breakdown in thunderstorms can begin with oppositely-directed fast breakdown of negative polarity, similar and in addition to fast positive breakdown expected from conventional dielectric theory and recent observations. The discovery of fast negative breakdown calls for an addendum to the physical description of electrical discharges in air. Recent studies have shown that lightning is initiated by a newly-recognized discharge process called fast positive breakdown. Here, the authors present observational evidence of fast breakdown but of negative polarity, seemingly contrary to current understanding of discharge physics.
Wiley
Spontaneous Emergence of Space Stems Ahead of Negative Leaders in Lightning and Long Sparks
Malagón‐Romero A., Luque A.
Geophysical Research Letters scimago Q1 wos Q1 Open Access , 
2019-03-20,  citations by CoLab: 34 ,  Abstract  
We investigate the emergence of space stems ahead of negative leaders. These are luminous spots that appear ahead of an advancing leader mediating the leader's stepped propagation. We show that space stems start as regions of locally depleted conductivity that form in the streamers of the corona around the leader. An attachment instability enhances the electric field leading to strongly inhomogeneous, bright and locally warmer regions ahead of the leader that explain the existing observations. Since the attachment instability is only triggered by fields above 10 kV/cm and internal electric fields are lower in positive than in negative streamers, our results explain why, although common in negative leaders, space stems and stepping are hardly observed if not absent in positive leaders. Further work is required to fully explain the streamer to leader transition, which requires an electric current persisting for timescales longer than the typical attachment time of electrons, around 100 ns.
American Geophysical Union
Characterizing Upward Lightning With and Without a Terrestrial Gamma Ray Flash
Smith D.M., Bowers G.S., Kamogawa M., Wang D., Ushio T., Ortberg J., Dwyer J.R., Stock M.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2018-09-25,  citations by CoLab: 32 ,  Abstract  
We compare two observations of gamma-rays before, during, and after lightning flashes initiated by upward leaders from a tower during low-altitude winter thunderstorms on the western coast of Honshu, Japan. While the two leaders appear similar, one produced a terrestrial gamma-ray flash (TGF) so bright that it paralyzed the gamma-ray detectors while it was occurring, and could be observed only via the weaker flux of neutrons created in its wake, while the other produced no detectable TGF gamma-rays at all. The ratio between the indirectly derived gamma-ray fluence for the TGF and the 95% confidence gamma-ray upper limit for the gamma-ray quiet flash is a factor of $1\times10^7$. With the only two observations of this type providing such dramatically different results -- a TGF probably as bright as those seen from space and a powerful upper limit -- we recognize that weak, sub-luminous TGFs in this situation are probably not common, and we quantify this conclusion. While the gamma-ray quiet flash appeared to have a faster leader and more powerful initial continuous current pulse than the flash that produced a TGF, the TGF-producing flash occurred during a weak gamma-ray "glow", while the gamma-ray quiet flash did not, implying a higher electric field aloft when the TGF was produced. We suggest that the field in the high-field region approached by a leader may be more important for whether a TGF is produced than the characteristics of the leader itself.
American Geophysical Union
Characteristics of Radio Emissions Associated With Terrestrial Gamma‐Ray Flashes
Mailyan B.G., Nag A., Murphy M.J., Briggs M.S., Dwyer J.R., Rison W., Krehbiel P.R., Boggs L., Bozarth A., Cramer E.S., Roberts O.J., Stanbro M., Rassoul H.K.
Journal of Geophysical Research Space Physics scimago Q1 wos Q2 , 
2018-07-02,  citations by CoLab: 26 , 
American Geophysical Union
Gamma Ray Showers Observed at Ground Level in Coincidence With Downward Lightning Leaders
Abbasi R.U., Abu‐Zayyad T., Allen M., Barcikowski E., Belz J.W., Bergman D.R., Blake S.A., Byrne M., Cady R., Cheon B.G., Chiba J., Chikawa M., Fujii T., Fukushima M., Furlich G., et. al.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2018-05-17,  citations by CoLab: 64 ,  Abstract  
Bursts of gamma ray showers have been observed in coincidence with downward propagating negative leaders in lightning flashes by the Telescope Array Surface Detector (TASD). The TASD is a 700~square kilometer cosmic ray observatory located in southwestern Utah, U.S.A. In data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower-producing flashes were obtained with a 3D lightning mapping array, and electric field change measurements were obtained for an additional seven flashes, in both cases co-located with the TASD. National Lightning Detection Network (NLDN) information was also used throughout. The showers arrived in a sequence of 2--5 short-duration ($\le$10~$\mu$s) bursts over time intervals of several hundred microseconds, and originated at an altitude of $\simeq$3--5 kilometers above ground level during the first 1--2 ms of downward negative leader breakdown at the beginning of cloud-to-ground lightning flashes. The shower footprints, associated waveforms and the effect of atmospheric propagation indicate that the showers consist primarily of downward-beamed gamma radiation. This has been supported by GEANT simulation studies, which indicate primary source fluxes of $\simeq$$10^{12}$--$10^{14}$ photons for $16^{\circ}$ half-angle beams. We conclude that the showers are terrestrial gamma-ray flashes (TGFs), similar to those observed by satellites, but that the ground-based observations are more representative of the temporal source activity and are also more sensitive than satellite observations, which detect only the most powerful TGFs.
Found 47
By date By citations
American Geophysical Union
Energetic Compact Strokes as the Major Source of Downward Terrestrial Gamma‐Ray Flashes in Winter Thunderstorms
Wu T., Smith D.M., Wada Y., Nakazawa K., Oguchi M., Kamogawa M., Suzuki T., Yang Q., Wang D.
Geophysical Research Letters scimago Q1 wos Q1 Open Access , 
2025-03-24,  citations by CoLab: 0 ,  Abstract  
AbstractTerrestrial gamma‐ray flashes (TGFs) are short bursts of intense gamma radiation associated with lightning discharges. Although thousands of TGFs have been observed from space, TGFs detected at ground level, known as downward TGFs, are still very limited, and their relationship with lightning discharge processes remains elusive. Here we report a special type of strong negative lightning stroke, termed energetic compact stroke (ECS), in winter thunderstorms in Japan, and provide strong evidence that ECSs are consistently associated with downward TGFs. Based on this relationship, we successfully identified three new downward TGFs by the observations of ECSs. Further, 12 out of 19 (63%) of downward TGFs analyzed in this paper were associated with ECSs, indicating that ECSs are the major source of downward TGFs in winter thunderstorms in Japan. These findings open up the possibility of remotely monitoring a large fraction of downward TGFs with simple lightning observations.
American Geophysical Union
An Upward Multi‐Pulse TGF Involved With Two Thunderstorm Cells
Nakazawa K., Oguchi M., Wu T., Wada Y., Okuma K., Wang D., Tsuji Y., Omiya Y., Ando M., Enoto T., Tsurumi M., Kataoka J., Kanda T., Iwashita R., Koshikawa N., et. al.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2025-03-18,  citations by CoLab: 0 ,  Abstract  
AbstractGamma rays associated with lightning discharges are evidence of MeV electrons acceleration by electric field in the atmosphere. However, the acceleration site and actual condition of it are not yet identified. On 30 December 2021, a terrestrial gamma ray flash (TGF) with five (or six) consecutive pulses were detected by our gamma ray detectors placed in Kanazawa City, Japan. Although analog signals of the detectors were severely saturated, timing of the five gamma ray pulses were well constrained and compared with radio observations of discharges. We detected four slow positive radio pulses associated with the first four gamma ray pulses. Another radio pulse candidate associated with the fifth gamma ray pulse was also seen. The polarity of the slow pulses suggests that the TGF were upward directed, and our detectors were observing it backward. This is the first detection of this kind on ground. The radio slow pulses were located in a thunderstorm cell located 3–6 km south from a nearly simultaneously on‐going ascending negative stepped leader emerged in another thunderstorm cell. These results suggest that the TGF's acceleration location can be a few km apart from the leader development of the main discharge activity. We also found another ascending negative stepped leader emerging ms after the TGF near the region where the five slow radio pulses took place.
American Geophysical Union
Observation of the First Stepping Process of Three Winter Lightning Discharges
Yang Q., Wang D., Yang J., Wu T.
Geophysical Research Letters scimago Q1 wos Q1 Open Access , 
2025-02-17,  citations by CoLab: 1 ,  Abstract  
AbstractUsing three different lightning observation systems, we have observed the first stepping processes of three lightning discharges with unprecedented details. We found that each of the first stepping processes contains a clear upward fast negative breakdown (FNB) corresponding to the preliminary breakdown (PB) pulse peak. Prior to the FNB from the lightning initiation, most sources are located in a fan‐shape area, and the FNB grows from this area forming a channel with a length from 45 to 120 m. During the period of about 100 microseconds immediately preceding the PB pulse, multiple 1–12 MHz radio bursts are located within or near the fan shape area. These radio bursts may indicate stem/space leaders. Eventually the FNB decayed and scattered in another fan shape area at the upper end of the channel. Based on these findings, we have proposed a complete picture of the first stepping process.
American Geophysical Union
First Time‐Resolved Leader Spectra Associated With a Downward Terrestrial Gamma‐Ray Flash Detected at the Telescope Array Surface Detector
Kieu N., Abbasi R.U., Saba M.M., Belz J.W., Krehbiel P.R., Stanley M.A., Gordillo‐Vazquez F.J., Passas‐Varo M., Warner T., Rison W., Rodeheffer D., da Silva D.R., Mazzucco D., Knight T., Cruz I.T., et. al.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2024-12-10,  citations by CoLab: 0 ,  Abstract  
AbstractOptical emissions associated with Terrestrial Gamma ray Flashes (TGFs) have recently become important subjects in space‐based and ground‐based observations as they can help us understand how TGFs are produced during thunderstorms. In this paper, we present the first time‐resolved leader spectra of the optical component associated with a downward TGF. The TGF was observed by the Telescope Array Surface Detector (TASD) simultaneously with other lightning detectors, including a Lightning Mapping Array (LMA), an INTerFerometer (INTF), a Fast Antenna (FA), and a spectroscopic system. The spectroscopic system recorded leader spectra at 29,900 frames per second (33.44 s time resolution), covering a spectral range from 400 to 900 nm, with 2.1 nm per pixel. The recordings of the leader spectra began 11.7 ms before the kA return stroke and at a height of 2.37 km above the ground. These spectra reveal that optical emissions of singly ionized nitrogen and oxygen occur between 167 s before and 267 s after the TGF detection, while optical emissions of neutrals (H I, 656 nm; N I, 744 nm, and O I, 777 nm) occur right at the moment of the detection. The time‐dependent spectra reveal differences in the optical emissions of lightning leaders with and without downward TGFs.
American Geophysical Union
Intermediate Fluence Downward Terrestrial Gamma Ray Flashes as Observed by the Telescope Array Surface Detector
Abbasi R.U., Kieu N., Krehbiel P.R., Belz J.W., Saba M.M., Rison W., Stanley M.A., Rodeheffer D., Mazzucco D., Knight T., da Silva D.R., Cruz I.T., Remington J., Mazich J., LeVon R., et. al.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2024-12-10,  citations by CoLab: 0 ,  Abstract  
AbstractOn 11 September 2021, two small thunderstorms developed over the Telescope Array Surface Detector (TASD) that produced an unprecedented number of six downward terrestrial gamma ray flashes (TGFs) within one‐hour timeframe. The TGFs occurred during the initial stage of negative cloud‐to‐ground flashes whose return strokes had increasingly large peak currents up to 223 kA, 147 GeV energy deposit in up to 25 1.2 km‐spaced surface detectors, and intermittent bursts of gamma‐rays with total durations up to 717 s. The analyses are based on observations recorded by the TASD network, complemented by data from a 3D lightning mapping array, broadband VHF interferometer, fast electric field change sensor, high‐speed video camera, and the National Lightning Detection Network. The TGFs of the final two flashes had gamma fluences of and 8, logarithmically bridging the gap between previous TASD and satellite‐based detections. The observations further emphasize the similarity between upward and downward TGF varieties, suggesting a common mechanism for their production.
American Geophysical Union
Continuous Initial Breakdown Development of In‐Cloud Lightning Flashes
Pu Y., Cummer S.A.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2024-10-24,  citations by CoLab: 2 ,  Abstract  
AbstractUsing a 30–250 MHz VHF interferometer, we observed a previously unreported mode of initial lightning development inside thunderclouds. This mode is defined by continuous VHF radiation spanning several km within the first few milliseconds of lightning initiation. Following flash initiation through fast positive breakdown at high altitudes above 9 km, the VHF radiation front of upward negative streamers ascended continuously at a speed of ∼1.0 × 106 m/s, forming a continuous initial breakdown burst (CIBB) about 2 km in length. For the two CIBBs analyzed, the long and narrow CIBB channel was traversed by dart leaders that occurred later in the flash, indicating that the CIBB channel belongs to what becomes the main conducting leader channel. In contrast to classic initial breakdown pulses (IBPs) with sub‐pulses superimposed on the rising edge, CIBBs produced a series of discrete, narrow LF pulses (<10 μs) with an average time interval of 0.20 and 0.14 ms, respectively. We speculate that a CIBB is a continuously developing negative streamer system in the high electric field region at high altitudes, with connections of internal plasma channels producing LF pulses. These results have implications for physical conditions conducive to the formation of a long and continuous negative streamer system.
Springer Nature
Flickering gamma-ray flashes, the missing link between gamma glows and TGFs
Østgaard N., Mezentsev A., Marisaldi M., Grove J.E., Quick M., Christian H., Cummer S., Pazos M., Pu Y., Stanley M., Sarria D., Lang T., Schultz C., Blakeslee R., Adams I., et. al.
Nature scimago Q1 wos Q1 , 
2024-10-02,  citations by CoLab: 13 ,  Abstract  
Two different hard-radiation phenomena are known to originate from thunderclouds: terrestrial gamma-ray flashes (TGFs)1 and gamma-ray glows2. Both involve an avalanche of electrons accelerated to relativistic energies but are otherwise different. Glows are known to last for one to hundreds of seconds, have moderate intensities and originate from quasi-stationary thundercloud fields2–5. TGFs exhibit high intensities and have characteristic durations of tens to hundreds of microseconds6–9. TGFs often show a close association with an emission of strong radio signals10–17 and optical pulses18–21, which indicates the involvement of lightning leaders in their generation. Here we report unique observations of a different phenomenon, which we call flickering gamma-ray flashes (FGFs). FGFs resemble the usual multi-pulse TGFs22–24 but have more pulses and each pulse has a longer duration than ordinary TGFs. FGF durations span from 20 to 250 ms, which reaches the lower boundary of the gamma-ray glow duration. FGFs are radio and optically silent, which makes them distinct from normal TGFs. An FGF starts as an ordinary gamma-ray glow, then suddenly increases exponentially in intensity and turns into an unstable, ‘flickering’ mode with a sequence of pulses. FGFs could be the missing link between the gamma-ray glows and conventional TGFs, whose absence has been puzzling the atmospheric electricity community for two decades. Flickering gamma-ray flashes associated with terrestrial thunderstorms have been observed, which may be the missing link between gamma-ray glows and TGFs.
American Geophysical Union
Evidence of a New Population of Weak Terrestrial Gamma‐Ray Flashes Observed From Aircraft Altitude
Bjørge‐Engeland I., Østgaard N., Sarria D., Marisaldi M., Mezentsev A., Fuglestad A., Lehtinen N., Grove J.E., Shy D., Lang T., Quick M., Christian H., Schultz C., Blakeslee R., Adams I., et. al.
Geophysical Research Letters scimago Q1 wos Q1 Open Access , 
2024-09-07,  citations by CoLab: 2 ,  Abstract  
AbstractTerrestrial Gamma‐ray Flashes (TGFs) are ten‐to‐hundreds of microsecond bursts of gamma‐rays produced when electrons in strong electric fields in thunderclouds are accelerated to relativistic energies. Space instruments have observed TGFs with source photon brightness down to ∼1017–1016. Based on space and aircraft observations, TGFs have been considered rare phenomena produced in association with very few lightning discharges. Space observations associated with lightning ground observations in the radio band have indicated that there exists a population of dimmer TGFs. Here we show observations of TGFs from aircraft altitude that were not detected by a space instrument viewing the same area. The TGFs were found through Monte Carlo modeling to be associated with 1015–1012 photons at source, which is several orders of magnitude below what can be seen from space. Our results suggest that there exists a significant population of TGFs that are too weak to be observed from space.
American Geophysical Union
Spectral Hardness of X‐ and Gamma‐Ray Emissions From Lightning Stepped and Dart Leaders
Contreras‐Vidal L., Sanchez J.T., da Silva C.L., Sonnenfeld R.G., Aulich G., Edens H.E., Eack K.B., Smith D.M.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2024-04-13,  citations by CoLab: 1 ,  Abstract  
AbstractDuring the 2022 New Mexico monsoon season, we deployed two X‐ray scintillation detectors, coupled with a 180 MHz data acquisition system to detect X‐rays from natural lightning at the Langmuir Lab mountain‐top facility, located at 3.3 km above mean sea level. Data acquisition was triggered by an electric field antenna calibrated to pick up lightning within a few km of the X‐ray detectors. We report the energies of over 240 individual photons, ranging between 13 keV and 3.8 MeV, as registered by the LaBr3(Ce) scintillation detector. These detections were associated with four lightning flashes. Particularly, four‐stepped leaders and seven dart leaders produced energetic radiation. The reported photon energies allowed us to confirm that the X‐ray energy distribution of natural stepped and dart leaders follows a power‐law distribution with an exponent ranging between 1.09 and 1.96, with stepped leaders having a harder spectrum. Characterization of the associated leaders and return strokes was done with four different electric field sensing antennas, which can measure a wide range of time scales, from the static storm field to the fast change associated with dart leaders.
American Geophysical Union
Imaging Step Formation in In‐Cloud Lightning Initial Development With VHF Interferometry
Pu Y., Cummer S.A.
Geophysical Research Letters scimago Q1 wos Q1 Open Access , 
2024-01-03,  citations by CoLab: 4 ,  Abstract  
AbstractWe investigate sequential processes underlying the initial development of in‐cloud lightning flashes in the form of initial breakdown pulses (IBPs) between 7.4 and 9.0 km altitudes, using a 30–250 MHz VHF interferometer. When resolved, IBPs exhibit typical stepped leader features but are notably extensive (>500 m) and infrequent (∼1 millisecond intervals). Particularly, we observed four distinct phases within an IBP stepping cycle: the emergence of VHF sources forming edge structures at previous streamer zone edges (interpreted as space stem/leader development), the fast propagation of VHF along the edge structure (interpreted as the main leader connecting the space leader), the fast extension of VHF beyond the edge structure (interpreted as fast breakdown), and a decaying corona fan. These measurements illustrate clearly the processes involved in the initial development of in‐cloud lightning flashes, evidence the conducting main leader forming, and provide insights into other processes known to occur simultaneously, such as terrestrial gamma ray flashes.
American Geophysical Union
XStorm: A New Gamma Ray Spectrometer for Detection of Close Proximity Gamma Ray Glows and TGFs
Pallu M., Celestin S., Hazem Y., Trompier F., Patton G.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2023-12-21,  citations by CoLab: 1 ,  Abstract  
AbstractIn this paper, we present XStorm, a gamma ray spectrometer developed to detect gamma ray glows and terrestrial gamma ray flashes (TGFs) in close proximity. Measurements are mostly planned to take place on balloon campaigns but also on the ground using bigger detectors. The main aim in developing XStorm is to perform new in situ and close proximity measurements of those events to improve the understanding of the physical processes involved. For that, we ensured XStorm reached performances adapted to glow and TGF detections. It detects photons with energy between ∼400 keV and ∼20 MeV. Detected particles are timetagged with a 600 ns precision with respect to UTC. Using two types of scintillator, Bismuth Germanium Oxide and EJ‐276 plastic associated with SiPMs, the instrument is able to discriminate three types of particles involved in those events: photons, neutrons, and electrons. The behavior of the detector under high particle fluxes has been quantified through ground testing using a pulse generator. A triggered detection system has been developed, with different thresholds depending on the target of study. First measurements have been carried out with test flights in fair weather conditions and are presented here. Estimations of the configurations in which a gamma ray glow can be detected by XStorm and of the number of TGFs that could be detected in specific campaigns are also addressed.
MDPI
Estimates of Lightning Activity and Terrestrial Gamma-ray Flash Detectability at Mount Etna for the ESTHER Project
Ursi A., Reitano D., Virgilli E., Bulgarelli A., Tiberia A.
Atmosphere scimago Q2 wos Q4 Open Access , 
2023-12-15,  citations by CoLab: 0 ,  PDF,  Abstract  
The Experiment to Study Thunderstorm High-Energy Radiation (ESTHER) is a small project of the Italian National Institute for Astrophysics (INAF), devoted to the study of high-energy emissions from thunderstorms, such as Terrestrial Gamma-ray Flashes and gamma-ray glows, which will start in 2024. In order to reduce the absorption typically undergone by gamma-ray radiation in the lower layers of the atmosphere and make these events detectable on the ground, the ESTHER set-up will be installed at high altitudes on Mt. Etna (Italy). We carried out a detailed analysis of lightning occurrence in this geographic region in order to test how suitable such a location is for the installation of a detection system to investigate thunderstorms and related emissions. The analysis pointed out a strong clustering of lightning in the proximity of the mountain peak and over the main volcano craters, where the frequent presence of volcanic ashes could increase, under the conditions of humid air typical of thunderstorms, electrical conductivity. An estimate of the gamma-ray absorption in the air undergone by typical TGF radiation allowed us to evaluate the suitability of two possible installation sites suggested for the project. This study represents a preliminary work for ESTHER and serves as a launching pad for future analyses.
Institute of Electrical and Electronics Engineers (IEEE)
Effect of Spherical Wavefronts on Very-High-Frequency (VHF) Lightning Interferometer Observations
Fan X., Krehbiel P.R., Stanley M.A., Zhang Y., Rison W., Edens H.E.
IEEE Transactions on Geoscience and Remote Sensing scimago Q1 wos Q1 , 
2023-11-07,  citations by CoLab: 1 , 
American Geophysical Union
Analysis of Narrow Bipolar Events Using Mode Decomposition Methods
Senay S., Krehbiel P.R., da Silva C.L., Edens H.E., Bennecke D., Stanley M.A.
Journal of Geophysical Research Atmospheres scimago Q1 wos Q2 , 
2023-10-26,  citations by CoLab: 2 ,  Abstract  
AbstractMulti‐resolution analysis methods can reveal the underlying physical dynamics of nonstationary signals, such as those from lightning. In this paper we demonstrate the application of two multi‐resolution analysis methods: Ensemble Empirical Mode Decomposition (EEMD) and Variational Mode Decomposition (VMD) in a comparative way in the analysis of electric field change waveforms from lightning. EEMD and VMD decompose signals into a set of Intrinsic Mode Functions (IMFs). The IMFs can be combined using distance and divergence metrics to obtain noise reduction or to obtain new waveforms that isolate the physical processes of interest while removing irrelevant components of the original signal. We apply the EEMD and VMD methods to the observations of three close Narrow Bipolar Events (NBEs) that were reported by Rison et al. (2016, https://doi.org/10.1038/ncomms10721). The ΔE observations reveal the occurrence of complex oscillatory processes after the main NBE sferic. We show that both EEMD and VMD are able to isolate the oscillations from the main NBE, with VMD being more effective of the two methods since it requires the least user supervision. The oscillations are found to begin at the end of the NBEs' downward fast positive breakdown, and appear to be produced by a half‐wavelength standing wave within a weakly‐conducting resonant ionization cavity left behind in the wake of the streamer‐based NBE event. Additional analysis shows that one of the NBEs was likely initiated by an energetic cosmic ray shower, and also corrects a misinterpretation in the literature that fast breakdown is an artifact of NBE‐like events in interferometer observations.
Institute of Electrical and Electronics Engineers (IEEE)
An Improved Method for Analyzing Broadband VHF Interferometer Lightning Observations
Fan X., Krehbiel P.R., Stanley M.A., Rison W., Edens H.E., Zhang Y.
IEEE Transactions on Geoscience and Remote Sensing scimago Q1 wos Q1 , 
2023-07-27,  citations by CoLab: 4 , 

Top-30

Journals

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12
Journal of Geophysical Research Atmospheres
Journal of Geophysical Research Atmospheres, 12, 26.09%
Geophysical Research Letters
Geophysical Research Letters, 9, 19.57%
Remote Sensing
Remote Sensing, 3, 6.52%
IEEE Transactions on Geoscience and Remote Sensing
IEEE Transactions on Geoscience and Remote Sensing, 3, 6.52%
Science China Earth Sciences, 2, 4.35%
Atmosphere
Atmosphere, 2, 4.35%
SCIENTIA SINICA Terrae, 2, 4.35%
Journal of Geophysical Research Space Physics
Journal of Geophysical Research Space Physics, 1, 2.17%
Atmospheric Measurement Techniques
Atmospheric Measurement Techniques, 1, 2.17%
Galaxies
Galaxies, 1, 2.17%
Scientific Reports
Scientific Reports, 1, 2.17%
Journal of Atmospheric and Solar-Terrestrial Physics
Journal of Atmospheric and Solar-Terrestrial Physics, 1, 2.17%
Electric Power Systems Research
Electric Power Systems Research, 1, 2.17%
Plasma Sources Science and Technology
Plasma Sources Science and Technology, 1, 2.17%
Journal of Physics G: Nuclear and Particle Physics
Journal of Physics G: Nuclear and Particle Physics, 1, 2.17%
Journal of Instrumentation
Journal of Instrumentation, 1, 2.17%
Journal of Physics: Conference Series
Journal of Physics: Conference Series, 1, 2.17%
Earth and Space Science
Earth and Space Science, 1, 2.17%
Topics in Applied Physics
Topics in Applied Physics, 1, 2.17%
Nature
Nature, 1, 2.17%
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10
12

Publishers

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8
10
12
14
16
American Geophysical Union
American Geophysical Union, 16, 34.78%
Wiley
Wiley, 7, 15.22%
MDPI
MDPI, 6, 13.04%
Science in China Press, 4, 8.7%
IOP Publishing
IOP Publishing, 4, 8.7%
Springer Nature
Springer Nature, 3, 6.52%
Institute of Electrical and Electronics Engineers (IEEE)
Institute of Electrical and Electronics Engineers (IEEE), 3, 6.52%
Elsevier
Elsevier, 2, 4.35%
Copernicus
Copernicus, 1, 2.17%
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16
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