1. The Sun Youra Taroyan

2. Age 4.5 ×10 9 years Mean diameter 1.392×10 6 km, 109 × Earth Mass 1.9891×10 30 kg, 333,000 × Earth Volume 1.412×10 18 km 3, 1,300,000 × Earth

3. Motivation 1. Understanding how the Sun affects the Earth and the near space environment (Space weather) 2. The Sun as a star 3. Natural plasma laboratory

6. The H-R diagram Stars fall into concentrated groups in the H-R diagram Each concentration defines a particular class Why white dwarfs or red giants?

7. Unlike any other star, we can observe the Sun in detail The atmosphere of the Sun viewed by the SDO spacecraft in various channels which cover temperatures from 5000K to 15MK. All of these structures are moving

8. Plasmas 99% of the known universe is in plasma state

9. Looking inside the Sun “The singing Sun” In the 1960s it was suggested that sound waves could travel around the inside of the Sun, being reflected at the surface and refracted by the changing density and temperature inside the Sun These waves can interfere to produce standing waves in the Sun, moving areas of the surface in and out – and this produces small (but measurable!) Doppler-shifts in the wavelengths of the Sun's light All modes1 mode3 modes

11. Solar material is hot and structured into different layers with different properties. The Sun contains a layer which acts as a dynamo, generating a strong magnetic field

12. Sun doesn't rotate as one mass Breakdown in rigid rotation near base of convection zone (tachocline)‏ Different variation in rotation rate with depth at different latitudes Bands of high- and low-speed flow at different latitudes and depths in the Sun These bands move over time

13. Galileo’s drawings of sunspots

17. The 11-year solar cycle

18. http://umbra.nascom.nasa.gov/images/latest.html Increasing temperature Sun shows more structure (more complexity) at higher temperatures Sun isn't as simple as it looks in white-light images

19. Chromosphere - the "coloured sphere" Seen during total eclipse (or in H-  line)‏ Thin layer ~ 2000 km deep Temperature ~ 6000 K at base, increases with height to 20000 K Low density Glows red (Hydrogen-  emission)‏ Chromosphere is hotter than Photosphere - how? Probably heated by sound waves from photosphere

20. Filaments and Prominences Two names for the same thing On the disc of the Sun: Dark channels – Filaments Relatively cool, dense gas suspended above the chromosphere Off the limb of the Sun: See the loop of material against the sky Bright suspended Prominences May erupt!

21. Fine-scale structures above the solar limb – Hinode imager

22. XIX century drawings of a solar eclipse

23. The Solar Corona

24. Coronal heating problem

25. Coronal Loops

26. Solar minimum and maximum