On the global anisotropy of cosmic ray data above 4 × 1019 eV

Soebur Razzaque, John P. Ralston

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


The distribution of arrival directions of ultra-high energy cosmic rays may yield clues to their mysterious origin. We introduce a method of invariant statistics to analyse cosmic ray data which eliminates coordinate-dependent artifacts. When combined with maximum likelihood analysis, the method is capable of quantifying deviations of the distribution from isotropy with high reliability. We test our method against published AGASA events with energies above 4 × 1019 eV. Angular cuts from observational limitations are taken into account. A model based on the Fisher distribution reveals the rotation of the Earth with the axis n along the direction (5h 53.36m, 85.78°) in (RA, DEC) coordinates, which is within 5° of the equatorial north pole. Global anisotropy of the data, if any, hinges on finer understanding of detector acceptance than what is available from the published literature.

Original languageEnglish
Pages (from-to)95-103
Number of pages9
JournalJournal of Cosmology and Astroparticle Physics
Issue number7
Publication statusPublished - Jul 2003
Externally publishedYes


  • Cosmic ray detectors
  • Cosmic rays
  • Ultra high energy cosmic rays

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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