SOLAR DIURNAL AND SEMI-DIURNAL VARIATIONS OF COSMIC-RAYS OBSERVED BY THE NORTH-SOUTH NETWORK OF SURFACE-LEVEL MULTIDIRECTIONAL MUON TELESCOPES

A scintillator muon telescope was installed at the Hobart Campus of th e University of Tasmania (42.85 degrees 8, 147.42 degrees E), Australi a in December 1991. It is part of a North-South Network of Multi-Direc tional Cosmic Ray Muon Surface Telescopes, in conjunction with the Nag oya Cosmic Ray Muon Telescope (35.12 degrees N, 136.97 degrees E). Usi ng two years of data from the North-South Network, we have investigate d the average features of the solar diurnal and semi-diurnal variation s. Preliminary results of the analysis show that two years averages of the observed diurnal variations are composed of a north-south symmetr ic and an asymmetric variations. The north-south asymmetric diurnal va riation is consistent with that expected from the semi-diurnal anisotr opy which produces the observed semi-diurnal variation. It is shown th at the reference axis of the anisotropy is in the direction of about 7 degrees S sunward from the ecliptic.