Full size image at http://science.msfc.nasa.gov/ssl/pad/solar/images/bfly.gif The image above is called a "Butterfly Diagram" based on how it looks or a "Maunder Diagram" based on its discoverer. What it shows is that at the start of each 11 year cycle, sunspots are formed mostly at latitudes on the Sun of around + or - 30 degrees. Then as time goes by, those sunspots fade and new sunspots are formed closer to the equator. This gives the butterfly shape. Also, more sunspots are formed as the average location for sunspots moves towards the equator of the Sun. Then you start to get fewer sunspots as they get right near the equator--finally the cycle starts over. The Sun is more "active" when there are more sunspots, and even though sunspots are cooler than the rest of the Sun, the Sun may be brighter at "solar max" when the most sunspots are visible. By more "active", we mean that there are more eruptions on the surface of the Sun, such as solar flares. Solar flares can result from the tangled up magnetic field finding a way of untangling fast that gives off a lot of energy--like twisted up rubber bands snapping back to place. The solar flares can be extremely energetic and send particles through space on their way to Earth. Also, the corona of the Sun (hot gas surrounding it) can be affected by the sunspot cycle and solar activity. The corona is probably kept hot by both sound waves from the Sun and by waves along the magnetic field lines (like waves on a string). Sometimes there are coronal mass ejections that send gas out into space. If the magnetic field lines of the Sun are open then gas flowing along the lines can escape the Sun into a high speed solar wind.
The causes of the Sunspot Cycle		What causes the sunspot cycle? Our best understanding is that it is the result of the differential rotation of the Sun mucking up the magnetic field at its surface. Here is an illustration of what happens to the Sun's magnetic field as a result of the Sun's differential rotation: This can explain much of what we know about the Sunspot cycle. The sunspots start out at higher latitude and then form closer to the equator, because the magnetic field gets twisted up more near the equator the longer you wait for the rotation. Sunspots often come in pairs like a magnet--one for the north pole and the other for the south pole. The one that's "leading", has the same polarity as the pole of the Sun in that hemisphere. (Example: in the North hemisphere of the Sun, you'd see from left to right the South and then North pole of a sunspot-pair.) Then when sunspots meet near the equator, the north and south cancel out--you start to get fewer sunspots near the end of the cycle. If you have SN in that order, and the N spot cancels out a S spot from the south pole, you end up with a S spot in the northern hemisphere and a N spot in the southern hemisphere. It's thought that these can act to cancel out the North and South poles themselves, so that every 11 years, the North and South poles of the Sun reverse! This last happened about a year ago.
The Sunspot Cycle's effect on the Earth		The sunspot cycle can have important effects on the Earth! For one, look what happened from about 1645 through 1715: observers found very few sunspots compared with before or after. It turns out that this was a time of colder temperatures, especially in Europe, and in fact this time is often called the "Little Ice Age." The Sun may have been 0.25 percent dimmer during this period! Also, solar flares can disrupt power grids and satellite communications. They can be dangerous for astronauts above the Earth's atmosphere. But they can also create beautiful auroras near the poles!