The highest energy cosmic ray particles are the most energetic particles
known to us in the universe, and their observations have led us to build
one
of the largest detector system in the world, the AUGER air-shower array.
We
have detected particles to 3×1020 eV, which is a macroscopic
energy.
There are a number of options how to generate them, and how to get these
particles from their sources to us. The various source families separate
themselves into several classes, but one main difference is to argue on
the
one hand, that these particles are accelerated to the high energy in a
shock
wave, such as in a radio galaxy, or some other shock-wave, and on the
other,
that they are the product of a decay of a very massive particle, possibly
connected to dark matter. One key is the lack of understanding of the
cosmological web of magnetic fields, which may influence the propagation
of
high energy particles.
I will discuss the observational and theoretical
limits for an exemplary set of models, and also the predictions, that
result
from these models. Detailed observations may allow us not only to set
limits
to the cosmic magnetic field, but also to some aspects of particle
physics.
Now that we are beginning to accumulate data, the role of the magnetic
field
in the bending is becoming crucial, and I will discuss the strategies that
are necessary to decide what Nature is doing. Very powerful radio
galaxies
could turn out to be the best accelerators in the universe, ready to allow
us to study particle physics at energies inaccessible on Earth.