  We present the results of 720 hours of observations of transient solar events
at ground level, during the summer season 2005 (Souther Hemisphere). Data were
taken with the TUPI muon telescope, working at a high counting rate (up to 100
KHz) and always pointing on the IMF lines (45 degrees of pitch angle). An
anti-correlation among the arrival of keV protons (observed by EPAM detector
aboard the ACE spacecraft) and sudden depressions in the muon flux at sea level
have been observed. The phenomena is discussed in the context that they can be
considered as mini-Forbush, caused by a shielding effect of the passage of a
disturbance (shock and plasma) and may be a signature of interplanetary
manifestations of coronal mass ejections.
