Status of extensive air shower studies at the Pierre Auger Observatory

The construction of the Southern site of the Pierre Auger Observatory is now essentially finished. While the total acceptance accumulated so far only amounts to about one year of the completed detector, i.e. ∼ 7000 km 2 sr yr , a number of valuable results could be reached about the highest energy cosmic ray spectrum (above a few 10 18 eV ), the evolution of composition indicators as a function of energy, photon and neutrino flux limits, and the arrival directions of the ultra-high-energy cosmic rays (UHECRs). In particular, the first experimental evidence of their anisotropic distribution above ∼ 60 EeV was obtained. These results strongly suggest an extragalactic and bottom-up origin of the UHECRs, but do not yet allow us to determine either their mass distribution (nuclear type), or their sources. While these results are very encouraging for charged particle astronomy and individual source studies, significantly larger statistics will be needed to complete such an ambitious program.