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
Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above 1019 eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of 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 on the amplitudes of the dipole and 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 a symmetric quadrupole.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- Contributing Organization:
- Telescope Array collaboration
- DOE Contract Number:
- AC02-07CH11359; FR02-04ER41300: FG02- 99ER41107
- OSTI ID:
- 1162137
- Report Number(s):
- FERMILAB-PUB-14-325-AD-AE-CD-TD; arXiv eprint number arXiv:1409.3128
- Journal Information:
- Astrophysics Journal, Vol. 794, Issue 2
- Publisher:
- IOP Publishing
- Country of Publication:
- United States
- Language:
- English
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