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"Cosmic rays" are not the same as "cosmic radiation". Cosmic rays are charged (massive) particles which are moving at relativistic speeds, and are not electromagnetic radiation. In contrast, cosmic radiation consists of photons.

I see the wikipedia article for cosmic rays [0] does state they are radiation, which is misleading and should probably be changed.

[0] https://en.wikipedia.org/wiki/Cosmic_rays

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Cosmic rays are particle radiation [0], so its not misleading to state that they are radiation.

[0] http://en.wikipedia.org/wiki/Particle_radiation

Yes, you're correct. My bad. Though, in my experience, "radiation" without a modifier almost always refers to the electromagnetic variety. But I guess that could vary depending on what circles one hangs out in.

IME in physics, the term "radiation" usually refers to particles whose total energy is much greater than their rest mass. Not all free electrons constitute beta radiation; only those whose velocity is some considerable fraction of the speed of light. Massless particles such as photons, on the other hand, are always radiation according to that definition.

This. In medicine, for instance, "radiation" without a modified almost always refers to "ionizing radiation" --ie with enough energy to induce DNA damage by creating free radicals or inducing covalent linkages.

It can be correct but still misleading. I think, depending on the reader, there's a good chance it's misleading.

Cosmic Rays are often started from one singular particle, but by the time they hit the atmosphere, they cause air showers large and small. This is because there's not a whole lot to interact with in space, but there's tons of matter once you start hitting the atmosphere. At ultra high energies, cosmic rays cause extensive air showers leading to radiation in the form of gamma rays, muons, and electrons/positrons through pair production. The electrons are actually called the "electronic shower" There is a distance where the average energy of the photons in the shower is less than 1MeV, causing pair production to cease. This distance into the atmosphere is called Xmax, but it's dependent upon the amount of mass in the atmosphere, not the magnetic field. For lower energy cosmic rays, Xmax is pretty small. For higher energies, Xmax can easily hit us.

"Radiation" doesn't necessarily mean electromagnetic radiation. After all, alpha- and beta-rays are also called radiation all the time.

Rays usually means em-radiation. But cosmic rays are misnamed from (as they tend to be radiation, but not rays).

I'm getting lost in terminology: at least one source uses "cosmic radiation" in the exact opposite sense, as a synonym for cosmic rays:

http://pdg.lbl.gov/2008/reviews/rpp2008-rev-cosmic-rays.pdf

AFAIK the term "cosmic radiation" is not really specific. Cosmic rays are cosmic radiation, but the term does not exclusively refer to them.

I guess it depends on the field one is in. Confusing, though.