ABSTRACT
The study of the anisotropy of ultrahigh energy cosmic rays is clearly of great interest in determining their possible sources, as well as in studying the diffusion of particles through the galactic magnetic field. Anisotropy have used galactic coordinates because interpretation in terms of cosmic ray origin models is more straight-forward. Galactic coordinates have the equator in the galactic plane, and the north galactic pole is defined by a perpendicular to the galactic plane going through the sun's position in the galaxy. If sources are galactic and follow the galactic mass distribution, then anisotropy towards the galactic plane should be seen in the coordinate system. The most statistically significant data on anisotropy comes from the Haverah Park, Yakutsk, and Sydney experiments. The "Fly's Eye" experiment can also measure cosmic ray anisotropy, but using a rather different technique. "Fly's Eye" data on anisotropy can only be used for completely clear moonless nights, since clouds can cause unknown variations in acceptance.
