S. Mori et al., OBSERVATION OF THE NORTH-SOUTH ASYMMETRY OF SIDEREAL ANISOTROPY OF COSMIC-RAYS AT MATSUSHIRO UNDERGROUND, Journal of Geomagnetism and Geoelectricity, 47(11), 1995, pp. 1097-1102
We present the observed results of the cosmic-ray sidereal anisotropy
in the primary rigidity range 550-950 GV from the Matsushiro undergrou
nd (geogr. 36.5 degrees N, 138.0 degrees E; 220 m.w.e. depth) for the
period 1984-1994. The muon telescope used is of multi-directional with
17 channels,which scan simultaneously over the median latitude of vie
wings from similar to 60 degrees N to similar to 15 degrees S on the c
elestial sphere. We obtain significant sidereal diurnal and semi-diurn
al terms in the daily variations with several s.d., being consistent w
ith other observations. Most notably, the north-south asymmetry in the
diurnal variations is confirmed without solar modulation, in which th
e amplitude increases as the direction of viewings of the telescopes m
oves southward towards and over the equator.