Multi-Station Characterisation of Forbush Decreases in Long-Term Neutron Monitor Observations

Forbush decreases (FDs) are transient reductions in galactic cosmic ray intensity near Earth, commonly associated with solar-driven interplanetary disturbances. Their measured properties can depend on the observing station and the procedures used to identify and characterise individual events. We analyse long-term hourly neutron monitor observations from Oulu, Lomnický štít, Newark, and Dourbes using a common detection and empirical profile-fitting framework. Candidate FDs are identified from relative count-rate reductions over 12–48 h intervals and manually verified, while duplicate, complex, and stepwise events unsuitable for the adopted single-component model are excluded. Each retained event is fitted with a modified skew-normal profile to determine its amplitude and characteristic times. The resulting catalogues contain 157, 115, 163, and 240 events for Oulu, Lomnický štít, Newark, and Dourbes, respectively, including 49 events identified at all four stations. Median amplitudes are broadly similar among the datasets, whereas duration distributions show stronger station-to-station differences. These differences are reduced, but not eliminated, for the matched-event subset. The amplitude–duration relationship is weak and station-dependent, while onset-to-minimum time correlates positively with total duration but only weakly with the post-minimum recovery duration. The results show that station response and operational parameter definitions must be considered when comparing FD properties derived from different neutron monitor observations.