Invited talk for the XVI International Symposium on Very
High Energy Cosmic Ray Interactions (ISVHECRI 2010), Batavia, IL, USA.
For a PDF version of the article, click here.
astro-ph/1011.4467
Abstract: I review what is known and surmised about magnetic fields in space, from our Milky Way environment to the distant Universe beyond the GZK horizon. This includes our gradually improving specification of the CR propagation environment within the Milky Way, the nearby universe within ~ 10 Mpc, and out to the GZK "horizon" near 100 Mpc. Within these modest intergalactic distances we hope for some pointing capability for CR energies above ~ 1019 eV, and for different species, as the observed event numbers accumulate in this range over the near future. The wider intergalactic propagation environment beyond the GZK horizon is also discussed. It sets a useful context for understanding other types of anisotropies, including sources of HE photons, neutrinos, leptons, etc. and for understanding relative time of arrival differences, such as those produced by lepton-photon cascades in the intergalactic medium. The global layout of potential UHECR sources is likely connected with the large scale structure (LSS) of cosmic filaments and voids, at least within ~ 100 Mpc. Possible source candidates for UHECR production are discussed, at various redshift ranges up to z ~ 2. Candidates discussed are AGN-jet sources, Centaurus A and more distant giant radio galaxies, and the possible indirect role of galaxies having a strong magnetized CR gas outflow that is driven by "starbursts" involving multiple supernovae and other energetic stellar events. Various analysis methods are described. I also discuss the current state of the results and near-future prospects for improving them.
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