Solar Activity Chapter 8 Section 3

Observing the sun DO NOT LOOK DIRECTLY AT THE SUN!!! In the 17th century Galileo observed the sun and saw spots on it surface, day by day he noticed that these spots moved across the sun. He concluded that the sun was a sphere and was rotating.

Sunspots 1) Sunspots are cool spots on the sun’s surface caused by strong magnetic fields. A typical sunspot is about twice the size of EARTH!! They can last a few weeks to as long as two months Umbra- dark core and the Penumbra is the outer, lighter region

Sunspots 2) The number of these sunspots follow an 11 year cycle, at max there are more than 100 visible spots and min, very few. Early in the cycle, spots appear in the high latitudes and later near the equator- when plotted it looks like butterfly wings, which is called Maunder butterfly diagram. 3)The Zeeman effect gives astronomers a way to measure the strength of magnetic fields on the sun- astronomers look for spectral line split in a spectrograph

4) The sunspot cycle can vary over centuries and appears to affect Earth’s climate- There were a few sunspots from 1645-1715 –This was called the Maunder minimum-coincides with the “little ice age” 5) Sunspots are part of a larger magnetic process that involves all layers of the sun’s atmosphere

The sun’s magnetic cycle Sun spots are a magnetic phenomena, which means the 11 year cycle must be caused by cyclical changes in the sun’s magnetic field The sun does not rotate as a rigid body (like Earth does) Some parts of the sun rotate faster than other parts The equatorial region rotates the fastest At the equatorial region the photosphere rotates once every 25 days, but higher up it is rotating about 28 days This is called differential rotation

The Sun’s magnetic cycle Energy flows outward through the layers of the sun. The gas is highly ionized, so it is a good conductor of electricity When the electrical conductor rotates rapidly and is stirred by convection, it can convert some of the energy flowing outward into a magnetic field. This process is called the dynamo effect. The magnetic field is generated a the bottom of the convection zone

The sun’s magnetic cycle BABCOCK MODEL TEXT PAGE 178