The graphics represent solar cycles 21-24. The red line is the monthly smoothed sunspot number while the blue line is the monthly sunspot number. Cycle 21 started in June 1976 with a smoothed sunspot number of 12.2. Cycle 23 began in May 1996 with the monthly SSN at 8.0 and peaked in April 2000 at 120.8. Cycle 24 began in December 2008 with the monthly SSN at 1.7.
Cycle 24 is expected to peak either late in 2012 or sometime during 2013. Taking into consideration the strong increase in sunspot numbers since May 2011, the current projection is for a smoothed sunspot number maximum at 105 +/- 20. This means that cycle 24 has some resemblance to cycles 10 and 23.
This page is maintained by Jan Alvestad once a month. Provided that credit is given, the graphics can be freely copied. Data source: Sunspot Index Data Center in Brussels.
[Solar Terrestrial Activity Report]