Cosmic ray intensity variations observed at Matsushiro (220 M.W.E. in depth)

Cosmic ray data from Matsushiro underground station were analyzed for four years (1981 to 84). It is found that a marked semi-annual intensity variation has been observed in this period. Solar diurnal and semi-diurnal variations have also been observed. After correcting for the spurious sidereal diurnal variation arising from the anisotropy responsible for the solar semi-diurnal variation (Nagashima et al., 1983), it is found that the corrected sidereal diurnal variation is consistent with those so far reported.