  Numerous authors have suggested that the ultra-high energy cosmic rays
(UHECR) detected by the Pierre Auger Observatory and other cosmic-ray
telescopes may be accelerated in the nuclei, jets or lobes of radio galaxies.
Here I focus on stochastic acceleration in the lobes. I show that the
requirement that they accelerate protons to the highest observed energies
places constraints on the observable properties of radio lobes that are
satisfied by a relatively small number of objects within the
Greisen-Zat'sepin-Kuzmin (GZK) cutoff; if UHECR are protons and are accelerated
within radio lobes, their sources are probably already known and catalogued
radio galaxies. I show that lobe acceleration also implies a (charge-dependent)
upper energy limit on the UHECR that can be produced in this way; if lobes are
the dominant accelerators in the local universe and if UHECR are predominantly
protons, we are unlikely to see cosmic rays much higher in energy than those we
have already observed. I comment on the viability of the stochastic
acceleration mechanism and the likely composition of cosmic rays accelerated in
this way, based on our current understanding of the contents of the large-scale
lobes of radio galaxies, and finally discuss the implications of stochastic
lobe acceleration for the future of cosmic ray astronomy.
