In‐Flight Observation of Positron Annihilation by ILDAS
Peer reviewed, Journal article
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Original versionKochkin P, Sarria D, Skeie CA, Van Deursen AP, de Boer A, Bardet M, Allasia C, Flourens F, Østgaard N. In‐Flight Observation of Positron Annihilation by ILDAS. Journal of Geophysical Research - Atmospheres. 2018;123(15):8074-8090 https://doi.org/10.1029/2018jd028337
We report a 511‐keV photon flux enhancement that was observed inside a thundercloud and is a result of positron annihilation. The observation was made with the In‐flight Lightning Damage Assessment System (ILDAS) on board of an A340 test aircraft. The aircraft was intentionally flying through a thunderstorm at 12‐km altitude over Northern Australia in January 2016. Two gamma ray detectors showed a significant count rate increase synchronously with fast electromagnetic field variations registered by an on‐board antenna. A sequence of 10 gamma ray enhancements was detected, each lasted for about 1 s. Their spectrum mainly consists of 511‐keV photons and their Compton component. The local electric activity during the emission was identified as a series of static discharges of the aircraft. A full‐scale Geant4 model of the aircraft was created to estimate the emission area. Monte Carlo simulation indicated that the positrons annihilated in direct vicinity or in the aircraft body.