The anisotropy of arrival directions of cosmic rays above 1017 eV

A detailed analysis of the world's data on ultra-high energy cosmic rays, which come from measurements of extensive air showers, reveals clear evidence for anisotropies in their arrival directions at energies below about 1019 eV. Confidence in this conclusion comes from consistency, within the errors, of the results from the different experiments and a correlation between independent indicators of anisotropy. Although models of the Galactic magnetic field topology are not yet precise, we have used one such to estimate the fraction of cosmic rays which are light nuclei as a function of energy. (author)