Where do astrophysical neutrinos come from?

What I really do not get about them is collisions of cosmic rays with light produces high energy neutrinoes but cosmic rays have a little energy maybe less than a 5000 electron volt. How do high energy neutrinoes come from such little energy?

Can any one please explain me this?

• Where did you get the 5keV limit from? That's totally false. – CuriousOne Feb 1 '16 at 15:42
• @CuriousOne: My guess would be OP is thinking of solar energetic particles, though 5 keV isn't an upper bound there either. – Kyle Kanos Feb 1 '16 at 15:53
• – Kyle Kanos Feb 1 '16 at 15:56
• @KyleKanos: I see... that's not quite cosmic rays, then. Solar neutrinos peak at 300keV for the pp-process and way higher for the rest, so even the sun is producing much higher energy radiation. :-) – CuriousOne Feb 1 '16 at 15:58

There are very high energetic cosmic rays. The most energetic cosmic rays measured by the Auger observatorium for example have energies in excess of $10^{19}$ eV. They measure a few of those per year. At these energies they are no longer able to identify what type of particle it is, but it is believed to be predominantly protons and iron.