The Anisotropy of Cosmic Ray Arrival Directions around 10${}^{18}$eV

Abstract

Anisotropy in the arrival directions of cosmic rays with energies above 10${}^{17}$eV is studied using data from the Akeno 20 km${}^2$ array and the Akeno Giant Air Shower Array (AGASA), using a total of about 117,000 showers observed during 11 years. In the first harmonic analysis, we have found strong anisotropy of $\sim$ 4% around 10${}^{18}$eV, corresponding to a chance probability of 0.2%. With two dimensional analysis in right ascension and declination, this anisotropy is interpreted as an excess of showers near the directions of the Galactic Center and the Cygnus region.

17 pages with 16 figures, http://www.icrr.u-tokyo.ac.jp/~erina/English.html