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Cosmic rays and the EMS

  1. Mar 6, 2006 #1
    Are cosmic rays part of the EMS (Electromagnetic spectrum)? I have seen duagrams showing that cosmic rays are part of the EMS and I have heard conflicting reports that cosmic rays are not part of the EMS. I know cosmic rays are energetic nuclei and have mass so I tend to believe that they are not part of the EMS but some scientist seem to inlude them on EMS diagrams. Thanks RAD
  2. jcsd
  3. Mar 6, 2006 #2
  4. Mar 6, 2006 #3


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    Historically, before CRs were particularly well understood, gammas (part of the "EMS") which came from outside the atmosphere were lumped into 'cosmic rays'.

    It's been quite a while (50 years? more?) since the distinction between cosmic rays (the particles) and high-energy gammas became clear-cut.

    If you see some diagrams with "cosmic rays" way down at the high energy end of the electromagnetic spectrum, I think you're seeing an echo of those earlier days.

    Alternatively, you may be seeing a confusion, or a too-drastic editing. The universe is pervaded by EM, with energies ranging from the plasma frequency cutoff (up in the long-wavelength radio part) to TeV gammas (and beyond? that's an active area of research). At the high energy end, the gammas can have energies that are comparable to energies of cosmic rays, so perhaps an editor added 2 and 2 and got 5?
  5. Mar 7, 2006 #4
    I think the only known source of really high energy gammas is cosmic rays.I also think it is fairly hard to tell the difference between a "gamma or photon cosmic ray" and a "particle cosmic ray" in a cosmic ray detector, because they both initiate extensive air showers.
    I believe the percentage of cosmic rays that are photons is still somewhat uncertain, particularly at the highest energies, but they are thought to be the minority .i. e. only about one in a thousand. Google "cosmic ray photons" for some good refs.
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