Study on the long-period variations of galactic cosmic ray distribution in the interplanetary magnetic field

The data are analyzed of the Yakut complex of muon azimuthal telescopes located on the earth's surface and underground at a depth of 7, 20, and 60 m water equivalent during the observation period of 1971-1975. Beginning with 1960 the authors have observed a gradual displacement of the maximum of diurnal variations of muons from 18 hr local time to an earlier time. According to the data of all the installations of the Yakut underground complex, in 1971-1974 this displacement reached 3-4 hr