Sunspot numbers and proton events in solar cycles 19 to 24

In this study we compare the mean annual sunspot numbers for six most recent solar cycles (19 to 24) with number of energetic proton events occurring in those years. Though individual exhibit quite strong correlations, when they are combined into a generic cycle result is very significant (ρ = 0.98). For 21 24 (when spacecraft observations have been regularly available), also investigate variation source location relation four peak flux thresholds orders magnitude from ≥10 ≥10,000 pfu. helio-latitudes within ±40° (the range which active regions usually occur) there negligible helio-longitude regardless threshold. However, effect on varying threshold significant: higher closer median longitude 0°, being almost uniform pfu (32°W) (2°W). Finally, 10 19 pfu, all occurred between years 4 and 8 after minimum, were M- or X-class flares associated halo CMEs shock fronts, three intense (≥40,000 pfu) related 10–28°E. These results support extend previous work by cited authors, implications solar-terrestrial relations effects space weather geospace.