Almost Full Circle in Extreme Ultraviolet
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The Solar and Heliospheric Observatory (SOHO) celebrates its 12th launch anniversary on December 2. In late 1996, shortly after its launch, SOHO was able to observe the last minimum of the roughly 11-year activity cycle of the Sun. The minimum was followed by a rapid rise in solar activity, peaking 2001 and 2002. Activity levels have slowly declined since then, but we haven't reached solar minimum yet, despite passing 11.1 years since the last minimum — the average length of a solar cycle.
In fact, the sunspot cycles measured since the mid-18th century vary in length from 9.0 to 13.5 years, and while a team of experts assembled by NOAA, NASA, and ISES has attempted to predict when the next solar minimum will be, we won't really know until we get there. The experts, in fact, were sharply divided about the time of the next minimum and the intensity of the next maximum, which should arrive about 2012 or 2013.
Whenever the next cycle begins, SOHO will be there to observe it.
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