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Communication Dans Un Congrès Année : 2019

Compton Scattering Effects on the Spectral and Temporal Properties of Terrestrial Gamma-ray Flashes

W. Xu
  • Fonction : Auteur
V. P. Pasko
  • Fonction : Auteur
R. A. Marshall
  • Fonction : Auteur

Résumé

Terrestrial gamma-ray flashes (TGFs), first detected in 1994 by the Burst and Transient Source Experiment (BATSE) instrument aboard the Compton Gamma-Ray Observatory [ Fishman et al., Science, 264, 1313, 1994], are high-energy photon bursts produced in close association with lightning activity in the Earth's atmosphere. Recent analyses of TGF light curves measured by the Gamma-Ray Burst Monitor (GBM) on the Fermi satellite have revealed that 67% of TGF pulses detected are asymmetric with fall time significantly longer than rise time [ Foley et al., JGR, 119, 5931, 2014]. Moreover, using a low-frequency interferometric lightning mapping array, Lyu et al. [GRL, 43, 5516, 2016] have found that most of the initial leader steps and channels were tilted away from the vertical direction, suggesting that such tilted geometry could mislead the interpretation of position-dependent TGF observation from space. The importance of tilted source geometry has been repeatedly emphasized in previous studies, for example, by Hazelton et al. [GRL, 36, L01108, 2009] while investigating the dependence of TGF energy spectra on offset distances, by Fitzpatrick et al. [Phys. Rev. D, 90, 043008, 2014] while studying the temporal and spectral evolution of TGFs, and by Mailyan et al. [JGR, 121, 11346, 2016] while performing spectral analysis on individual TGF events measured by Fermi GBM.

Despite the increased emphasis, the tilted TGF geometry has not been investigated in detail in previous studies. In this work, using first-principles Monte Carlo simulations and characteristic TGF sources, we first quantify the increased Compton scattering effects on the temporal and spectral properties of TGFs induced by the tilted source geometry. Modeling results indicate that the source orientation is a critical parameter in TGF analysis and offset distance between the lightning source and satellite location cannot be used as a single parameter characterizing Compton scattering effects. Moreover, we show how the Compton scattering effects can explain the symmetric and asymmetric pulses measured by Fermi GBM and thereby estimate a characteristic timescale for TGF-producing processes.

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Dates et versions

hal-03563820 , version 1 (10-02-2022)

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W. Xu, Sebastien Celestin, V. P. Pasko, R. A. Marshall. Compton Scattering Effects on the Spectral and Temporal Properties of Terrestrial Gamma-ray Flashes. American Geophysical Union, 2019, San Francisco, United States. ⟨hal-03563820⟩
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