TGF Afterglows: A New Radiation Mechanism From Thunderstorms

Rutjes, Casper; Diniz, Gabriel; Ferreira, Ivan Soares; Ebert, Ute

doi:10.1002/2017gl075552

Cited by 22 publications

(36 citation statements)

References 68 publications

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“…The neutrons were detected through capture in LgPl that then releases photons with a characteristic energy of 2.223 MeV. The photons appeared on a millisecond time scale and with the characteristic energy signature of neutron capture, consistent with the TGF afterglow predicted by Rutjes et al ().…”

Section: Introductionsupporting

confidence: 83%

“…Therefore, the secondary gamma rays formed when a neutron is captured in a nucleus have energies of the order of a few MeV due to the energy released during capture. This is the mechanism of the TGF afterglow predicted by Rutjes et al (), and first measured by Bowers et al () in a downward directed TGF.…”

Section: Introductionsupporting

confidence: 61%

“…It appears when photons create neutrons by a photonuclear reaction, and these neutrons release photons at capture. This is the mechanism that creates a TGF afterglow after a TGF, as predicted by Rutjes et al ().…”

Section: Simulated Photon and Neutron Distributions In Space Time Amentioning

confidence: 69%

“…Our results can also be applied to an arbitrary source energy spectrum with arbitrary temporal characteristics by superposing the energy intervals with appropriate weights. The simulations showed a second photon pulse that is not directly related to the primary gamma ray, but results from collisions between neutrons and air molecules (Rutjes et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Modeling Neutron Emissions in High Energy Atmospheric Phenomena

et al. 2018

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Neutron emissions with different durations have been observed during thunderstorms. These neutrons can be produced by microsecond to millisecond fast Terrestrial Gamma‐ray Flashes correlated with lightning, or by Gamma‐ray Glows lasting several seconds to minutes. In both cases, the neutrons are produced through a photonuclear reaction of gamma rays in the energy range of 10 to 30 MeV with nuclei of air molecules. Here we present simulations of gamma‐ray beams propagating downward from different source altitudes. In our analysis the primary photons with energies between 10 and 30 MeV are separated into four energy intervals, each of 5 MeV width. From these data, arbitrary spectra of primary photons and of their products can be composed. Our results indicate that the neutrons are created essentially along the trajectory of the primary photons and that they reach ground within a transversal area of radius below 500 m. This lateral spreading is dominated by neutron diffusion due to collisions with air molecules. A secondary longer lasting photon pulse at sea level is predicted as well by our simulations. We have introduced this Terrestrial Gamma‐ray Flash afterglow already in (Rutjes et al. 2017, https://doi.org/10.1002/2017GL075552). It is due to neutron capture by air molecules, and it has recently been observed by Bowers et al. (2017, https://doi.org/10.1002/2017GL075071) and Enoto et al. (2017, https://doi.org/10.1038/nature24630).

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Section: Introductionsupporting

confidence: 83%

Section: Introductionsupporting

confidence: 61%

Section: Simulated Photon and Neutron Distributions In Space Time Amentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

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Modeling Neutron Emissions in High Energy Atmospheric Phenomena

et al. 2018

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“…When photonuclear reactions such as

^{14}

N +

γ \to

^{13}

N +

n

take place, neutrons are generated and thermalized in the atmosphere. They are finally captured by ambient nitrogen nuclei, and the nuclei then emit de‐excitation gamma rays (also known as “TGF afterglows”; Rutjes et al, ). Gamma‐ray fluxes of the de‐excitation emissions decay with a time constant of 50–60 ms, which is the time scale of neutron thermalization in sea level atmospheric pressure (Enoto et al, ).…”

Section: Downward Tgfs In the 2017–2018 Winter Seasonmentioning

confidence: 99%

High Peak‐Current Lightning Discharges Associated With Downward Terrestrial Gamma‐Ray Flashes

et al. 2020

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During 2017–2018 winter operation of the Gamma‐Ray Observation of Winter Thunderclouds experiment in Japan, two downward terrestrial gamma‐ray flashes (TGFs) that triggered atmospheric photonuclear reactions were detected. They took place during winter thunderstorms on 5 December 2017 and 9 January 2018 at Kanazawa, Ishikawa Prefecture, Japan. Each event coincided with an intracloud/intercloud discharge, which had a negative‐polarity peak current higher than 150 kA. Their radio waveforms in the low‐frequency band are categorized as a distinct lightning type called “energetic in‐cloud pulse” (EIP). Negative‐polarity EIPs have been previously suggested to be highly associated with downward TGFs, and the present observations provide evidence of the correlation between them for the first time. Furthermore, both of the downward TGFs followed “gamma‐ray glows,” minute‐lasting high‐energy emissions from thunderclouds. It is suggested that the negative EIPs took place with downward propagating negative leaders or upward positive ones developed in highly electrified regions responsible for the gamma‐ray glows.

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Library of simulated gamma-ray glows and application to previous airborne observations

Sarria

Østgaard

Marisaldi

et al. 2022

Preprint

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Gamma-Ray Glows (GRGs) are high energy radiation originating from thunderclouds, in the MeV energy regime, with typical duration of seconds to minutes, and sources extended over several to tens of square kilometers. GRGs have been observed from detectors placed on ground, inside aircraft and on balloons. In this paper, we present a general purpose Monte-Carlo model of GRG production and propagation. This model is first compared to a model from Zhou et al. ( 2016) relying on another Monte-Carlo framework, and small differences are observed. We then have built an extensive simulation library, made available to the community. This library is used to reproduce five previous gamma-ray glow observations, from five airborne campaigns: balloons from Eack et al. (1996b), Eack et al. (2000; and aircrafts from ADELE (Kelley et al., 2015), ILDAS (Kochkin et al., 2017) and ALOFT (Østgaard et al., 2019). Our simulation results confirm that fluxes of cosmic-ray secondary particles present in the background at a given altitude can be enhanced by several percent (MOS process), and up to several orders of magnitude (RREA process) due to the effect of thunderstorms' electric fields, and explain the five observations. While some GRG can be explained purely by the MOS process, E-fields significantly larger than E th (the RREA threshold) are required to explain the strongest GRGs observed. Some of the observations also came with in-situ electric field measurements, that were always lower than E th , but may not have been obtained from regions where the glows are produced. This study supports the claim that kilometer-scale E-fields magnitudes of at least the level of E th must be present inside some thunderstorms.

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TGF Afterglows: A New Radiation Mechanism From Thunderstorms

Cited by 22 publications

References 68 publications

Modeling Neutron Emissions in High Energy Atmospheric Phenomena

Modeling Neutron Emissions in High Energy Atmospheric Phenomena

High Peak‐Current Lightning Discharges Associated With Downward Terrestrial Gamma‐Ray Flashes

Library of simulated gamma-ray glows and application to previous airborne observations

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