1. Solar Activity
Chapter 8 Section 3

2. 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.

3. 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

4. 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

6. 4) The sunspot cycle can vary over centuries and appears to affect Earth’s climate- There were a few sunspots from –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

7. 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

8. 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

9. The sun’s magnetic cycle BABCOCK MODEL TEXT PAGE 178

10. Chromospheric and Coronal Activity
The magnetic field extends into the chromosphere and the corona
1) The the magnetic phenomena in the chromosphere and the corona is like magnetic weather- result as constantly changing magnetic fields on the sun trap ionized gas to produce arches and powerful outburst.
PROMINCE- seen during total eclipses at the edge of the solar disk

11. Chromospheric and Coronal Activity
2) solar flares- rise to maximum in minutes and decay within an hour. In about 8 minutes they send x-ray and UV photons to Earth, which increases ionization in our atmosphere. This can interfere with radio communication
Particles from flares can reach Earth hours or days later by solar wind, this disrupts navigation systems.
Solar flares can also cause surges in electrical power lines and cause damage to Earth’s satellites. What does this mean??

12. Chromospheric and Coronal Activity
3) Much of the solar wind comes from coronal holes where the magnetic field does not loop back into the sun.

13. The Solar constant
Even a small change in the sun’s energy output could produce dramatic changes in Earth’s climate.
When calculating the energy production of the sun we find that it results in what is called the solar constant- about 1360 Joules per square meter per sec ((J/s=W)/M2)
A change in the solar constant by 1% could change Earth’s average temperature by 1-2oC (Last Ice age-Earth’s average temperature was about 5oC cooler than it is now