The anisotropy of cosmic ray flux in Large Area Air Shower experiments

The sidereal anisotropy of cosmic rays with energy in the range of 1014–1015eV was obtained by using Large Area Air Show (LAAS) experiments which deployed extensive air shower (EAS) arrays in large part of Japan. The first harmonic amplitude and phase in a function of right ascension axis are (0.23±0.04)×10−2 and 0.4±0.7 hour, respectively, and those of the second harmonics are (0.06±0.04)×10−2 and 7.5±2.6 hour, respectively. The first harmonic amplitude are compared with the diffusive mode of cosmic ray propagation, which predicts the dependence of anisotropy amplitudes on primary cosmic ray rigidities. The exponent value of rigidity dependence of diffusion coefficient is estimated as 0.34±0.01, in good agreement with Kolmogorov type spectrum of turbulence of galactic magnetic filed. Although a sky map in equatorial coordinates indicates excess and deficit regions above the isotropic expectation, their deviations were consistent with statistical ones, and more statistics are required to point the region and the opening angle of them.