1. Conversations with the Earth Tom Burbine tburbine@framingham.edu

2. Figure 15.4

3. Temperature Density

4. Parts of Sun Core Core – 15 million Kelvin – where fusion occurs

5. Figure 15.4

6. Radiation zone Radiation zone – region where energy is transported primarily by radiative diffusion Radiative diffusion is the slow, outward migration of photons

7. Figure 15.13

8. Photons emitted from Fusion reactions Photons are originally gamma rays Tend to lose energy as they bounce around Photons emitted by surface tend to be visible photons Takes about a million years for the energy produced by fusion to reach the surface

9. Figure 15.4

10. Convection Zone Temperature is about 2 million Kelvin Photons tend to be absorbed by the solar plasma Plasma is a gas of ions and electrons Hotter plasma tends to rise Cooler plasma tends to sink

11. Figure 15.14

12. Granulation – bubbling pattern due to convection bright – hot gas, dark – cool gas Figure 15.14

14. Figure 15.10

15. Figure 15.4

16. Photosphere Photosphere is the solar surface Where photons escape into space

17. Sunspots Sunspots are on the photosphere Have temperatures of ~4,000 K Photosphere is 5,800 K

20. Sunspots Sunspots are regions of intense magnetic activity Charged particles tend to follow magnetic field lines A magnetic field exerts a magnetic force on moving electric charges

24. Sunspot Cycle The cycle has a period of approximately 11 years, but the interval between maxima can be as short as 7 years and as long as 15 years. Figure 15.21

25. Maunder Minimum Between 1645 and 1715, the sunspot activity virtually stopped Identified by E. W. Maunder from historical sunspot records http://science.nasa.gov/headlines/y2003/17jan_solcon.htm

26. Since sunspots are darker than the surrounding photosphere it might be expected that more sunspots would lead to less solar radiation. However, the surrounding margins of sunspots are hotter than the average, and so are brighter More sunspots increase the sun's brightness. http://upload.wikimedia.org/wikipedia/commons/0/0d/Solar-cycle-data.png

27. Figure 15.4

28. Atmosphere of the Sun Chromosphere – above the photosphere and below the corona Temperature is about 10,000 Kelvin Most of the Sun’s ultraviolet light is emitted from this region

29. See Corona during eclipse

30. Atmosphere of the Sun Corona – tenuous uppermost layer of the Sun’s atmosphere Temperature is about 1 million Kelvin Most of the Sun’s X-rays are emitted from this region

31. Corona Extends millions of kilometers into space Sun's corona is constantly being lost as solar wind.

32. Solar Wind Stream of charged particles continually blown outward from the Sun

33. STEREO STEREO (Solar TErrestrial RElations Observatory) is a solar observation mission which was launched in October 2006. Two identical spacecraft were launched into orbits that cause them to (respectively) pull further ahead of and fall gradually behind the Earth. The spacecraft will do stereoscopic imaging of the Sun and processes such as Coronal Mass Ejections.

34. Coronal Mass Ejections are large clouds of magnetized gas ejected into space by the sun

35. http://en.wikipedia.org/wiki/STEREO

36. http://www.nasa.gov/mission_pages/stereo/main/i ndex.htmlhttp://www.nasa.gov/mission_pages/stereo/main/i ndex.html

37. http://www.hulu.com/watch/63320/cosmos-the- lives-of-the-stars#s-p1-so-i0http://www.hulu.com/watch/63320/cosmos-the- lives-of-the-stars#s-p1-so-i0

38. Any Questions?