Cosmic Ray Muon Observation at Southern Space Observatory—SSO (29°S, 53°W)

Under an agreement on scientific cooperation between Brazil and Japan, a prototype detector of cosmic ray muons has been operating since March 2001 at Southern Space Observatory (SSO) located at Sao Martinho da Serra (29°S, 53°W), Brazil, in order to observe cosmic ray precursors of geomagnetic storms. This detector plays a key roll in the prototype network of muon observations together with two larger detectors operating in Japan and Australia. The planned extension of the detector in its size will complete the global coverage of our muon detector network. The prototype network has already discovered cosmic ray precursors of several magnetic storms, as reported by Munakata et al. (Munakata, K. et al.: 2000, J Geophys Res. 105, A12, pp. 27, 457–27, 468; Munakata K. et al.: 2001, Proceedings of ICRC.) We have also observed the Forbush Decreases (FDs), as well as the precursory enhancements of cosmic ray anisotropy preceding the onsets of geomagnetic storms. This report presents the description of the network and some results obtained since the prototype detector implementation.