Year to year variation of sidereal anisotropy of cosmic rays

Year to year variation of sidereal anisotropy of cosmic rays (approximately 1011eV) has been observed for 1948-76, in the data from meson telescopes at underground and sea level and from ion chamber. The phases of sidereal diurnal variation in this energy region showed a drastic change for the year of 1968-69 and 1974-75; the former time of which corresponds to the epoch of the polarity reveral of the sun's polar magnetic field and latter to solar activity minimum. The maximum time of sidereal diurnal variation is nearly in the direction towards midnight after being corrected for anti-sidereal vector which is produced from loss-cone effect of solar origin. This fact may suggest that even in the energy region of approximately 1011eV could be observed the galactic anisotropy of cosmic rays. (author)