As I recal from Astronomy 312 "Stars," the 11-year cycle of the sun is only weakly supported by solar-flare counts. Some scientists, as I recall, believe in a 22-year cycle, and some don't believe the flaring behavior is particularly cyclic at all.
--LAN3 Tue, 28 Oct 2003 20:20:02 -0500
But NASA is more than happy to reenforce the idea:
http://science.nasa.gov/ssl/pad/solar/sunspots.htm(check it out-- 400 years of data!)
--LAN3 Tue, 28 Oct 2003 20:26:15 -0500