Radiation Risk Assessment Associated with TGFs for Aircraft Passengers: Estimations of the Probability for a Commercial Flight to Be Hit by a TGF
Abstract
Terrestrial Gamma ray Flashes (TGFs) are bursts of high-energy photons lasting less than 100 μs [Fishman et al., JGR, 116, A07304, 2011]. They are produced in common thunderstorms [e.g., Chronis et al., BAMS, 97, 639, 2016 ; Splitt et al., JGR, 115, A00E38, 2010] and Briggs et al. [JGR, 118, 3805-3830, 2013] estimated in 2013 that more than 400,000 Fermi-GBM detectable TGFs are produced each year on Earth. With a typical production altitude between 10 and 15 km [Cummer et al., GRL, 38, L14810, 2011; GRL, 41, 8586-8593, 2014; GRL, 42, 7792-7798, 2015], TGF sources are close to commercial flight altitudes, and therefore these high-energy events could represent an additional exposure to ionizing radiation for aircraft passengers and aircrews [Dwyer et al., JGR, 115, D09206, 2010]. In a recent work, we showed that doses delivered by gamma rays have been seemed to be relatively low, whereas extremely high doses have been estimated to be delivered in the electron acceleration region although in compact areas (hundreds of meters of radius) [Pallu et al., JGR, 126, e2020JD033907, 2021]. Currently, in most of the countries, the monitoring of aircrews exposure, mainly driven by cosmic rays, is performed by software, but these systems ignore the possible TGF contribution. Therefore, the need for a thorough risk assessment associated with TGFs for aircraft passengers and aircrews is called for by the predicted doses. In this work, we present a statistical study using TGF data from the first Fermi-GBM TGF catalog [Roberts et al., JGR, 123, 4381-4401, 2018] and both simulated and real commercial flight routes, in order to estimate an upper bound of the probability for a commercial flight to find itself in a TGF electron acceleration region and draw conclusions about the overall risk incurred by aircrews.