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| Titel |
Optical Emissions Associated with Terrestrial Gamma-ray Flashes |
| VerfasserIn |
Wei Xu, Sebastien Celestin, Victor Pasko |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106450
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| Publikation (Nr.) |
 EGU/EGU2015-6123.pdf |
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| Zusammenfassung |
| Terrestrial Gamma-ray Flashes (TGFs) are high-energy photon bursts originating from the
Earth’s atmosphere. After their discovery in 1994 by the Burst and Transient Source
Experiment (BATSE) detector aboard the Compton Gamma-Ray Observatory [Fishman et al.,
Science, 264, 1313, 1994], this phenomenon has been further observed by the Reuven
Ramaty High Energy Solar Spectroscopic Imager (RHESSI) [Smith et al., Science, 307,
1085, 2005], the Fermi Gamma-ray Space Telescope [Briggs et al., JGR, 115, A07323, 2010]
and the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite [Marisaldi et al., JGR,
115, A00E13, 2010]. Measurements have correlated TGFs with initial development stages of
normal polarity intracloud lightning that transports negative charge upward (+IC) [e.g., Lu et
al., GRL, 37, L11806, 2010; JGR, 116, A03316, 2011]. Moreover, Østgaard et al. [GRL, 40,
2423, 2013] have recently reported, for the first time, space-based observations of
optical emissions from TGF-associated IC lightning flashes, and Dwyer et al. [GRL,
40, 4067, 2013] recently quantified optical emissions associated with TGFs based
on assumption that these emissions are similar to those produced by extensive air
showers. In the present study, we quantify optical emissions resulting from the
excitation of air molecules produced by the large population of electrons involved in
TGF events based on two possible production mechanisms: relativistic runaway
electron avalanches (RREAs) [Dwyer and Smith, GRL, 32, L22804, 2005] and
acceleration of thermal runaway electrons produced by high-potential intra-cloud
lightning leaders [e.g., Celestin and Pasko, JGR, 116, A03315, 2011; Xu et al., GRL,
39, L08801, 2012]. Using Monte Carlo simulations, we show that electron energy
distributions established from these two production mechanisms are inherently different
over the full energy range, and also substantially different from those produced in
extensive air showers. Moreover, we show that TGFs are most likely accompanied by
detectable levels of optical emissions and that the distinct optical features are of
significant interest for constraining and validating current TGF production models. |
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