On the left, time profile of neutrons for the Bolivia-Mexico event observed by the NM-64 in Mount Chacaltaya. The blue dashed line at 17:17 UT (13:17 local time) represents the time of the onset for the SXR intensity recorded by GOES. The red thick line corresponds to the running average for 20 min. The red dashed lines are ±1σ calculated without including the signal window. The abscissa corresponds to the time in UT. On the right, the statistical analysis following the same procedure described in this section. In this case, we obtained a significant excess equivalent to 32 σ. More details can be found in Sako et al. (2006).