If you have a fear of flying, then probably the last thing on your mind when you are 10 km above the ground is what might be going on in the depths of the galaxy. But airline pilots and cabin crew might want to brush up on their astroparticle physics. High-energy particles coming from violent galactic events mean that radiation exposure for aircrew is higher than it is for most people classified as radiation workers. But the type of radiation that they are exposed to is very different.
The majority of the exposure comes from cosmic radiation that originates outside our solar system. Violent events such as stellar flares, supernovae and the explosion of galactic nuclei produce a concoction of subatomic particles, primarily protons and electrons. The energies of these particles can be greater than 1020 eV – billions of times higher than in the most powerful particle accelerators – although such energetic particles are very rare. Nuclear particles, which comprise about 98% of the radiation, typically have energies that are between 100 MeV and 10 GeV per nucleon.
In the April issue of Physics World, Graeme Taylor of the National Physical Laboratory in the UK describes a proportional counter that can measure cosmic radiation in more detail.
