Searches for Large-Scale Anisotropy in the Arrival Directions of Cosmic Rays above 10^19 eV at the Pierre Auger Observatory and the Telescope Array.

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2014 vol. 794 p. 172 - 187

0004-637X

Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. Anunambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This canbe achieved by combining data from observatories located in both the northern and southern hemispheres. To thisend, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above 1019 eV ispresented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a seriesof anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above 1019 eV.No significant deviation from isotropic expectations is found throughout the analyses performed. Upper limits onthe amplitudes of the dipole and quadrupole moments are derived as a function of the direction in the sky, varyingbetween 7% and 13% for the dipole and between 7% and 10% for a symmetric quadrupole.