Earth receives shower of both solar and cosmic radiations every seconds. The Sun put up a heliosphere around the solar system and thus foreign high energy charged particles could not penetrate easily. Is there any other source most probably that lies within our solar system?


  1. Very high energy cosmic particle beyond 5.7 x 10^19 eV were observed by Pierre Auger Observatory in Argentina. (rare but the GZK limit seems to rule out distance sources)
  2. GZK limit roughly capped the upper energy level of cosmic ray as they are slowed due to CMB over vast distance
  • $\begingroup$ You many need to be more specific. The sun emits a large number of (high energy) particles, including neutrinos and alpha particles. This is generally known as the solar wind. Particles interacting with our atmosphere can also produce high-energy particles. Are there particular kinds of particles, or particular energy scales, you wish to focus on? $\endgroup$ Commented Apr 10, 2015 at 1:45
  • $\begingroup$ @zibadawa Timmy see note $\endgroup$
    – user6760
    Commented Apr 10, 2015 at 3:14
  • $\begingroup$ GZK limit rules out sources further than ~160 million light years - there's no way particles of similar energy could be created in solar system. $\endgroup$
    – Mithoron
    Commented Apr 10, 2015 at 11:48
  • 1
    $\begingroup$ Our Galaxy has only 100 thousand light years; even our whole Virgo Supercluster has only 110 million light-years diameter so it could come from outside of it. $\endgroup$
    – Mithoron
    Commented Apr 10, 2015 at 13:00
  • 1
    $\begingroup$ arxiv.org/abs/1411.0704 $\endgroup$ Commented Apr 11, 2015 at 1:32

1 Answer 1


Normally, the two main sources of cosmic rays are considered to be the Sun (solar energetic particles) and galactic or extragalactic sources, although extragalactic sources are more common. Surprisingly, though, there is a third source, a family of particles known as anomalous cosmic rays (see Hovestadt et al. (1973) and Garcia-Munoz et al. (1973)). These are particles - generally ionized nuclei of lighter elements - primarily originating from interstellar space with energies on the order of $\sim10$ to $\sim10^2\text{ MeV}$.

Anomalous cosmic rays are generally accelerated at the termination shock of the heliosphere, moving into the heliosheath. Some may then escape into the inner Solar System. Here's an image from Stone et al. (2005), which shows them as a distinct population from galactic cosmic rays:

enter image description here

Now, these particles are technically of interstellar origin, even though they are accelerated to great speeds only at the boundary of the Solar System. However, a related population may have been found in the Kuiper Belt (see Schwadron et al. (2002)), formed from grains there after collisions between objects. While these are not necessarily - or even likely - the dominant source of anomalous cosmic rays, they do exist, and thus constitute another source of cosmic rays inside the Solar System.


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