Every time the sun lashes out with another beautiful but potentially threatening solar flare or coronal mass ejection, we are reminded that the naturally occurring solar cycle is approaching a "solar maximum" in 2013 and that solar activity is on the ascent. But what does that mean? If you're having a hard time picturing an active ball of flaming nuclear fusion versus a less-active ball of flaming nuclear fusion, simply see above.
Solar maximum (and minimum) are terms that describe whether we are at a peak or a trough in the sun's natural 11-year cycle, and they are determined by counting the number of sunspots visible on the surface of the sun during a given cycle. The most recent minimum occurred in 2008 and the sun is now building toward another maximum - a shift in activity that is very clearly visible here.
[NASA]
