This article provides a brief summary of existing knowledge related to ionising radiation emitted from thunderstorms and the possible health effects on aircraft crew and passengers exposed to this radiation.
Terrestrial Gamma-ray Flashes (TGFs)
Terrestrial gamma-ray flashes (TGFs) are bursts of gamma rays produced in the Earth's atmosphere. TGFs have been recorded to last 0.2 to 3.5 milliseconds, and have energies of up to 20 MeV. It is speculated that TGFs are caused by intense electric fields produced above or inside thunderstorms and are associated with lightning. In both lightning and TGFs, the high-energy emissions are believed to occur when electrons in air travelling at very close to the speed of light collide with the nuclei of air atoms.
Aircraft exposure to TGFs
There are many unknowns, including the occurrence rate of TGFs relative to lightning, the effect of the aircraft triggering the lightning, and the frequency and lengths of electron acceleration regions in thunderstorms. The estimated dose received by an individual in an aircraft struck by TGF or lightning-energetic electrons is about 30 mSv. Thus, a significant number of aircraft occupants may receive a large radiation dose.