Natural sources of radiation
Sources of ionizing radiation

Cosmic rays are streams of high-energy charged particles that travel through space in all directions. They are deflected by magnetic fields, particularly the Earth's magnetic field, which reflects low-energy particles back into space. They are more prominent at the poles, where they interact with the atmosphere in the form of the aurora borealis.

Cosmic rays are made up of hydrogen nuclei (85%) and helium nuclei (12.5%). The remainder is made up of electrons,...