Page 30 - Curriculum Visions Dynamic Book

Sunspot cycles
Sunspot activity increases and decreases over time all across the Sun, making up an 11-year cycle. At the start of a cycle the number of spots increases, and all spots get bigger, beginning first near the poles, then spreading to the equator to make a pattern that resembles a butterfly.
After about 3 years into the cycle it reaches a stage called the sunspot maximum. Spots do not last through the whole cycle but have a lifetime about the same as the time it takes for the gases at any latitude to go once around the Sun.
At the sunspot maximum there can be 300 spots clustered into about ten groups, although a few groups will contain most of the spots. After this stage the number of sunspots gradually decreases to end the cycle. At the end of the cycle there may be just a few spots left.
 Changes in sunspot numbers over the past
four centuries. The time
of the Little Ice Age corresponded with very low sunspot numbers. No one
is yet sure whether this is a coincidence, or if the two features are related.
200
150
100
50
0 1600
1650 1700 1750
1800 1850
Year
1900 1950 2000
30
Number of sunspots