Anisotropy of cosmic ray intensity in air shower region

The meaning of the anisotropy of cosmic ray intensity is considered in connection with the magnetic field in the space between the source and the earth. The importance of the half-day variations is discussed together with the results of the author's recent observations. It is interesting to note that the anisotropy around 1018 eV might correspond to the Orion arm and corona because the energy dependence of anisotropy is associated with the Larmor radius and the scale of the magnetic field structure. For the energy region of 1014 approximately 1017 eV, the existence of clear anisotropy is not yet announced. But based on the author's group's 3 year shower observations with muon detector at Akeno, the existence of a half-day variation of about 0.4 % around 3 x 1015 eV is being validated. Although there remains much to be studied about the author's results, it seems certain that there exist quite different kinds of anisotropy between the energy regions of 1013 approximately 1014 eV and 1015 approximately 1016 eV. (Aoki, K.)