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The PAMELA instrument detected antimatter particles in the Earth's magnetosphere. What are the sources of these particles?

The answer to Source of high energy cosmic particles outlines the sources of cosmic rays in general, does it still hold true for antimatter particles?

B--rian
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Dave Gremlin
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    Anywhere where highly energetic reactions take place whose center-of-mass energy surpasses the rest-mass energy of 2*times some particle, this particle and its anti-particle counterpart can be created. – AtmosphericPrisonEscape Apr 17 '20 at 17:22
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    I don't know if this can put antiparticles into the magnetosphere, but it's cool and weird: https://en.wikipedia.org/wiki/Terrestrial_gamma-ray_flash – uhoh Apr 18 '20 at 00:52
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    Positrons can be created when cosmic ray particles collide with particles in the interplanetary (or interstellar) medium. There's some relevant info in this article from 1998, but I expect that our knowledge on this topic has expanded somewhat since then. ;) And of course experiments like PAMELA are designed to gather data to help decide between competing hypotheses. – PM 2Ring Apr 18 '20 at 04:31
  • @AtmosphericPrisonEscape I guess your comment from April 2020 is already the answer. If you don't mind, I add an answer focusing on pair production along the theme "Matter and antimatter particles are always produced as a pair". – B--rian Mar 12 '21 at 07:58

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Matter and antimatter particles are always produced as a pair. This particle physics' process is called pair production. If antimatter is detectable, it means that the antiparticle of a matter-antimatter-particle-pair was able to survive long enough to be detected, for instance due to relativistic effects, as explained e.g. by the Hyperphysics page on muons:

The measurement of the flux of muons at the Earth's surface produced an early dilemma because many more are detected than would be expected, based on their short half-life of 1.56 microseconds. This is a good example of the application of relativistic time dilation to explain the increased particle range for high-speed particles.

You will now correctly say that a muon is not antimatter, but I just used the muon as example that some particles (or antiparticles) may be detected even if they have a short half-life.

So, what are the sources of antimatter in the magnetosphere? Strictly speaking, the source (in the sense of "location") of pair creation will probably be in the magnetosphere itself, as said by atmosphericprisonescape:

Anywhere where highly energetic reactions take place whose center-of-mass energy surpasses the rest-mass energy of 2*times some particle, this particle and its anti-particle counterpart can be created.

I suppose the real question is: How is their enough energy for frequent pair production in the magnetosphere?

B--rian
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    I recommend that you remove the section on black holes from this answer. Black holes are irrelevant to Earth's magnetosphere. Also, the virtual particle explanation of Hawking radiation is only a heuristic, and it's a bit misleading. Please see https://physics.stackexchange.com/a/252236/123208 & https://physics.stackexchange.com/a/30601/123208 – PM 2Ring Mar 12 '21 at 09:21
  • @PM2Ring Good point, much appreciated. I shortened my answer accordingly. Do you have any further suggestions how I could improve my answer? – B--rian Mar 12 '21 at 09:49
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    I guess there might be some antimuons and even antiprotons in the magnetosphere, produced by cosmic ray collisions. We normally detect antimatter from the gamma rays produced when the antimatter annihilates with normal matter. The main antimatter signature we look for is 511 keV gamma rays, which is the primary product of positron + electron annihilation. Antiproton annihilation is a bit complicated, as I mentioned here: https://physics.stackexchange.com/a/451337/123208 – PM 2Ring Mar 12 '21 at 10:05
  • Kind of related: detection of interstellar antihydrogen: https://physics.stackexchange.com/a/590085/123208 – PM 2Ring Mar 12 '21 at 10:12