Cosmic rays are...electrons, protons and other atomic nuclei (c)! Strictly speaking, cosmic rays are any form of radiation reaching the top of the earth's atmosphere from space. For historical reasons, however, the study of cosmic ray photons (a) (gamma rays) is usually called gamma ray astronomy. Physicists commonly use the term cosmic rays to describe any type of cosmic radiation OTHER THAN photons (electrons, protons, and nuclei). The relatively new field of neutrino astrophysics is yet another branch of cosmic ray research.
A great majority of cosmic rays are protons and hydrogen nuclei, not to be confused with hydrogen and helium atoms (b). Normally, a nucleus is found at the center of an atom, but in the case of cosmic rays, extremely energetic processes rip nuclei away from atoms. This a very important distinction to make, since nuclei, composed of neutrons and protons, have a net electrical charge, while atoms do not. The effect of magnetic fields on charged nuclei is much greater than the effect of magnetic fields on atoms.
Cosmic rays should not be confused with sting rays, one of which is shown below. Sting rays are ocean creatures that use electricity to defend themselves and paralyze their victims (d).
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