They have been stripped of their electrons and so are ionised.
C in our atmosphere, which is used in radiocarbon dating, and in the production of cosmogenic nuclides in rocks at the Earth surface, which we use in cosmogenic nuclide dating[1-3].
So, these rays are essential for many applications in Quaternary Science, but where do they come from?
Cosmic rays (also called cosmic radiation) mainly comprise high energy nucleons (protons, neutrons and atomic nuclei).
About 90% are hydrogen nuclei (a single proton with an atomic number of 1).
The particles bounce about in the magnetic field of the remnant anomaly until they gain sufficient energy to escape the system, whereupon they become cosmic rays. It is now known that most cosmic rays are atomic nuclei.
Most are hydrogen nuclei, some are helium nuclei, and the rest heavier elements.
The relative abundance changes with cosmic ray energy — the highest energy cosmic rays tend to be heavier nuclei.
Although many of the low energy cosmic rays come from our Sun, the origins of the highest energy cosmic rays remains unknown and a topic of much research.
This drawing illustrates air showers from very high energy cosmic rays. When cosmic rays collide with atoms in our atmosphere, they cause a cascade of reactions – we call this the ‘cosmic ray cascade’.
The first interaction is when the high energy particles collide with nuclei in the upper atmosphere. A spallation reaction is a nuclear reaction where a highly energetic nucleon (usually a secondary cosmic-ray neutron of energy) collides with a target nucleus.
This causes the release of multiple particles (protons, neutrons and clusters).