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

摘要

Spherical harmonic moments are well-suited for capturing anisotropy at anyscale in the flux of cosmic rays. An unambiguous measurement of the full set ofspherical harmonic coefficients requires full-sky coverage. This can beachieved by combining data from observatories located in both the northern andsouthern hemispheres. To this end, a joint analysis using data recorded at theTelescope Array and the Pierre Auger Observatory above $10^{19}$ eV ispresented in this work. The resulting multipolar expansion of the flux ofcosmic rays allows us to perform a series of anisotropy searches, and inparticular to report on the angular power spectrum of cosmic rays above$10^{19}$ eV. No significant deviation from isotropic expectations is foundthroughout the analyses performed. Upper limits on the amplitudes of the dipoleand quadrupole moments are derived as a function of the direction in the sky,varying between 7% and 13% for the dipole and between 7% and 10% for asymmetric quadrupole.