Sun Spots


Solar Wind

Solar Magnetic Mean Field


Sunspots are dark areas on the solar surface, which were created by the suns magnetic field. The magnetic field within a Sunspot can be several thousand times stronger than the magnetic field of the earth. They are typically 2000 degrees cooler than their surrounding areas and the extent of a sunspot can be several times the size of the earth.
The Sunspot Number is a measure of the amount of sun- spots on the sun at any given point of time. When the Sunspot Number is plotted as a function of time, one can clearly see an 11 year cycle in the data. This is known as the solar cycle and is one of the most important characteristics of the suns magnetic activity.
By adding the position of the Sunspots to the plot, one obtains a so called butterfly diagram. This shows how the Sunspots migrate towards the equator as the solar cycle progresses.
The exact origin of the sunspots and the appearance of their magnetic field is still one of the biggest mysteries in sun research, and is yet to be explained.

Daily Sunspot Numbers are provided by the National Geophysical Data Center,

The Butterfly diagram data provided by Dr. David Hataway, can be found at

The middle image on the left shows the butterflydiagram mentioned above. The other images above and below show the number of Sunspots in 50 so called bins during one solar rotation. The population of spots in the bins is either coded in colour or indicated by the size of the bars.

The 50 bins of the Sunspots are identified with the keys of a piano. The lowest tone corresponds with the South Pole. Within one measurement period of one solar rotation the keys are played sequentially with a volume proportional to the number of spots.