Cosmic ray anisotropies at median primary rigidities between 100 AND 1000 GV

A large east-west detector array at Ottawa has monitored muon intensities at zenith angles between 450 and 900 since November 1976. Sidereal variations have been determined for seven zenith angle ranges corresponding to median primary rigidities (m.p.r.) between 100 and 950 GV. The observed sidereal diurnal variations increase monotonically in amplitude with m.p.r. from less than 1x10-4 for 100 GVto (7.2+-1.6)x10-4 for 960 GV and are consistent with an anisotropy having an equatorial projected amplitude of 10.x10-4, lower cutoff rigidity of 360 GV and direction 3.4h. The sidereal semidiurnal variation is significant at the 0.999 level, and is consistent with a second harmonic anisotropy of projected amplitude 4x10-4, cutoff rigidity 360 GV and direction 7.0h. The sidereal anisotropy shows no significant change between 1979 and 1980 when the sun's magnetic polarity appears to have reversed