Detection of terrestrial gamma ray flashes up to 40 MeV by the AGILE satellite

Marisaldi, M.; Fuschino, F.; Labanti, C.; Galli, M.; Longo, F.; Monte, E. Del; Barbiellini, G.; Tavani, M.; Giuliani, A.; Moretti, E.; Vercellone, S.; Costa, E.; Cutini, S.; Donnarumma, I.; Evangelista, Y.; Feroci, M.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Mereghetti, S.; Pacciani, L.; Rapisarda, M.; Soffitta, P.; Trifoglio, M.; Argan, A.; Boffelli, F.; Bulgarelli, A.; Caraveo, P. A.; Cattaneo, P. W.; Chen, Andrew; Cocco, V.; D’Ammando, F.; Paris, G. De; Cocco, G. Di; Persio, G. Di; Ferrari, A.; Fiorini, M.; Froysland, T.; Gianotti, F.; Morselli, A.; Pellizzoni, A.; Perotti, F.; Picozza, P.; Piano, G.; Pilia, M.; Prest, M.; Pucella, G.; Rappoldi, A.; Rubini, A.; Sabatini, S.; Striani, E.; Trois, A.; Vallazza, E.; Vittorini, V.; Zambra, A.; Zanello, D.; Antonelli, L. A.; Colafrancesco, S.; Gasparrini, D.; Giommi, P.; Pittori, C.; Preger, B.; Santolamazza, P.; Verrecchia, F.; Salotti, L.

doi:10.1029/2009ja014502

Cited by 205 publications

(219 citation statements)

References 35 publications

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“…They were first observed in 1994 from the Compton Gamma‐ray Observatory satellite (Fishman et al, 1994) and later confirmed by other space‐based observations (Briggs et al, 2010; Marisaldi et al, 2010; Smith et al, 2005). X‐rays have also been observed at closer proximity to the source with sensors on the ground and on balloons (Dwyer, 2004; Mallick et al, 2012; Moore et al, 2001) and in high‐voltage laboratory discharge experiments of long sparks (Babich et al, 2015; Dwyer et al, 2005; Kochkin et al, 2014, 2016).…”

Section: Introductionmentioning

confidence: 69%

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

Köhn

Chanrion

Neubert

2018

Geophysical Research Letters

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Bursts of X‐rays and γ‐rays are observed from lightning and laboratory sparks. They are bremsstrahlung from energetic electrons interacting with neutral air molecules, but it is still unclear how the electrons achieve the required energies. It has been proposed that the enhanced electric field of streamers, found in the corona of leader tips, may account for the acceleration; however, their efficiency is questioned because of the relatively low production rate found in simulations. Here we emphasize that streamers usually are simulated with the assumption of homogeneous gas, which may not be the case on the small temporal and spatial scales of discharges. Since the streamer properties strongly depend on the reduced electric field E/n, where n is the neutral number density, fluctuations may potentially have a significant effect. To explore what might be expected if the assumption of homogeneity is relaxed, we conducted simple numerical experiments based on simulations of streamers in a neutral gas with a radial gradient in the neutral density, assumed to be created, for instance, by a previous spark. We also studied the effects of background electron density from previous discharges. We find that X‐radiation and γ‐radiation are enhanced when the on‐axis air density is reduced by more than ∼25%. Pre‐ionization tends to reduce the streamer field and thereby the production rate of high‐energy electrons; however, the reduction is modest. The simulations suggest that fluctuations in the neutral densities, on the temporal and spacial scales of streamers, may be important for electron acceleration and bremsstrahlung radiation.

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Section: Introductionmentioning

confidence: 69%

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

Köhn

Chanrion

Neubert

2018

Geophysical Research Letters

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“…Concerning the maximal energy, the original BATSE detection of TGFs up to a few MeV [1,9] was superseded by the RHESSI detection up to 20 MeV [2,10]. Recently, the AGILE satellite showed that TGF spectrum extends well above 20 MeV [11] (Tavani et al, 2009, submitted to Nature), as confirmed also by the Fermi-GBM detector [12].…”

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confidence: 95%

Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes

Marisaldi¹,

Argan²,

Trois³

et al. 2010

Phys. Rev. Lett.

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Terrestrial gamma-ray flashes (TGFs) are very short bursts of high-energy photons and electrons originating in Earth's atmosphere. We present here a localization study of TGFs carried out at gamma-ray energies above 20 MeV based on an innovative event selection method. We use the AGILE satellite Silicon Tracker data that for the first time have been correlated with TGFs detected by the AGILE Mini-Calorimeter. We detect 8 TGFs with gamma-ray photons of energies above 20 MeV localized by the AGILE gamma-ray imager with an accuracy of ∼5-10° at 50 MeV. Remarkably, all TGF-associated gamma rays are compatible with a terrestrial production site closer to the subsatellite point than 400 km. Considering that our gamma rays reach the AGILE satellite at 540 km altitude with limited scattering or attenuation, our measurements provide the first precise direct localization of TGFs from space.

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“…This may be due to a difference in atmospheric density at ground and high mountains. In fact, a TGF spectrum on average extends to a few tens of MeV [38,39], or 100 MeVon rare occasions [36]. It is believed that TGFs occur at altitudes of 15-20 km [40].…”

Section: Characteristics Of -Ray Emissionsmentioning

confidence: 99%

Observation of thundercloud-related gamma rays and neutrons in Tibet

et al. 2012

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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 $40 min , was observed on July 22, 2010. The solar-neutron telescope detected significant -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 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 terrestrial gamma ray flashes up to 40 MeV by the AGILE satellite

Cited by 205 publications

References 35 publications

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

High‐Energy Emissions Induced by Air Density Fluctuations of Discharges

Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes

Observation of thundercloud-related gamma rays and neutrons in Tibet

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