Galactic Anisotropy of Cosmic Ray Intensity Observed by an Air Shower Experiment

We have monitored multi-TeV cosmic rays by a small air shower array in Tehran (35°43' N, 51°20' E, 1200 m = 890 gcm^-2). More than 1.1 × 10⁶ extensive air shower events were recorded. These observations enabled us to analyse sidereal variation of the galactic cosmic ray intensity. The observed sidereal daily variation is compared to the expected variation which includes the Compton-Getting effect due to the motion of the earth in the Galaxy. In addition to the Compton-Getting effect, an anisotropy has been observed which is due to a unidirectional anisotropy of cosmic ray flow along the Galactic arms.