Radio-Loud AGNs as the Sources of the Ultra-High Energy Cosmic Rays
We argue in favor of the hypothesis that UHECRs are accelerated in the jets of blazars. This hypothesis explains a number of unusual observations, including extra gamma-ray spectral components; unusual weakly-variable TeV gamma-ray blazars, including 1ES 0229+200 and 1ES 0347-121; flattening of the Stecker-Scully relation between GeV-TeV spectral index and redshift; and VHE gamma-ray production in FSRQs. Joint CTA and Fermi analysis of VHE blazars like KUV 00311-1938 can discriminate between photon-induced and UHECR-induced cascades. The search for gamma-ray echoes in the intergalactic magnetic field with strength B(IGMF) supports studies showing that B(IGMF) > 1e-18 G.