The Sunspot Cycle

The sunspot cycle, which last about 11 years, is an period of increasing and decreasing in the number of sunspots of the Sun. Sunspots, as the name suggests, are the spots on the Sun’s photosphere that appear darker than the surrounding. Sunspots have temperatures about 3000 Kelvin to 4500 Kelvin. Sunspots are the area of the Sun where magnetic activity is very active and intense. They have different shapes and sizes, up to 80000 kilometers and some can be visible from Earth without the aid of a telescope.

The number of sunspots increases and decreases over a period of time with a regular cycle of 11 years. However, each cycle can be from 8 to 14 years. The Sun is most active when the number of sunspots is highest. During the cycle, the frequency of sunspots’ appearance varies by location and time. During a solar maximum, most of the sunspots appear in the middle latitudes of the Sun and move to the equator at solar minimum. The intensity, frequency and locations of sunspots are affected by the Sun’s complex internal magnetic fields that are constantly changing. The Sun’s magnetic poles flip every 11 years.  Because of the constant activity of magnetic fields, a sunspot usually last from a few days to a few weeks and they are dispersed by magnetic pressure.

Sunspots are important for scientists to study the Sun because they are visual indicator of the Sun’s complex magnetic field. Thus, internal structure can be studied. Sunspots are the sites where magnetic fields are powerful and intense. They are the sites where solar many phenomena such as solar flares, coronal mass ejections are from. The sunspot cycle is part of a longer cycle, called the solar cycle, which last about 22 years, which the magnetic poles of the Sun return to original positions.  

Sources:

http://en.wikipedia.org/wiki/Sunspot

http://www.nasa.gov/mission_pages/earth/news/solarcycle-primer.html

http://en.wikipedia.org/wiki/Solar_cycle