The Galactic Magnetic Field and UHECR Optics
  A good model of the Galactic magnetic field is crucial for estimating the
Galactic contribution in dark matter and CMB-cosmology studies, determining the
sources of UHECRs, and also modeling the transport of Galactic CRs since the
halo field provides an important escape route for by diffusion along its field
lines. We briefly review the observational foundations of the Jansson-Farrar
2012 model for the large scale structure of the GMF, underscoring the robust
evidence for a N-to-S directed, spiraling halo field. New results on the
lensing effect of the GMF on UHECRs are presented, displaying multiple images
and dramatic magnification and demagnification that varies with source
direction and CR rigidity.
