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GZK Violation - a Tempest in a (Magnetic) Teapot?

Glennys R. Farrar·Tsvi Piran
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Abstract

The apparent lack of suitable astrophysical sources for the observed highest energy cosmic rays (UHECRs) within $\approx 20$ Mpc is the "GZK Paradox". We constrain representative models of the extra-galactic magnetic field structure by Faraday Rotation measurements; limits are at the $μ$G level rather than the nG level usually assumed. In such fields, even the highest energy cosmic rays experience large deflections. This allows nearby AGNs (possibly quiet today) or GRBs to be the source of ultra-high energy cosmic rays without contradicting the GZK distance limit.

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Glennys R. Farrar, Tsvi Piran. 2000-01-31. GZK Violation - a Tempest in a (Magnetic) Teapot?. https://doi.org/10.1103/physrevlett.84.3527

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