High-Impact Activity of Solar Cycle 23 A Review of the Great Geophysical Events and their Effects on Society during the Minimum and Maximum Years of Solar Cycle 23

Solar Cycle 23 began in May 1996, with a monthly smoothed sunspot number (SSN) of 8.0, and peaked in April 2000 at 120.8. When measured against the previous 22 cycles, Cycle 23 is an average cycle, ranking 10th in SSN amplitude. However, Cycle 23's sunspot maximum was considerably smaller than the previous two cycles and the second smallest of the past six. This solar cycle is now fast approaching sunspot minimum, which is expected to occur in 2007. I will briefly review Cycle 23's most important solar events and discuss the significant geophysical responses and the associated impacts on technological systems. I will also quantify Cycle 23's geophysical activity, and assess the relationship between a cycle's SSN amplitude and the occurrence of significant proton and geomagnetic storms. As solar minimum approaches, significant solar flares and coronal mass ejections are rare occurrences. This may suggest to some that systems vulnerable to space weather events will be spared during the solar minimum years. This presentation will highlight that while eruptive solar events are rare during solar minimum, significant space weather affects our technological infrastructure during all stages of the approximate 11-year cycle.