List of Topics and Lecturers

1. Welcome to the The First Joint Arizona/NSO Summer SchoolJune 11-16, NSO Sac Peak Observatory, NM Introduction to the Sun 6/17/06

2. List of Topics and Lecturers • Helioseismology • Rachel Howe, NSO, Tucson • Rudi Komm, NSO, Tucson • Solar Interior • Gordon Petrie, NSO, Tucson • Radiative Transfer • Han Uitenbroek, NSO, Sac Peak • Solar Magnetohydrodynamics • Randy Jokipii, UofA, Tucson • Photospheric and Chromospheric Magnetic Fields • K.S. Balasubramanian (Bala), NSO, Sac Peak • Solar-Energetic Particles • Joe Giacalone, UofA, Tucson • Space Weather • Tom Bogan, NCAR, Boulder Introduction to the Sun 6/17/06

3. List of Activities • Computer software programs • RASL/DASL CDs and workbooks • xsolar (Chris Russell, UCLA) • Solar wind, interplanetary magnetic fields • Helioseismology application widget (Rachel Howe) • Solar viewing through Hα telescopes • Outside of visitor center • Poster viewing/discussion Introduction to the Sun 6/17/06

4. List of Other Activities • Monday – reception at the director’s house • Tuesday – White Sands picnic • Wednesday – • Tour of NSO facilities, • Community BBQ • Thursday – Pizza Night / Star Party Introduction to the Sun 6/17/06

5. The Physics of the Sun Introduction to the Sun 6/17/06

6. Why Study the Sun ? • Influence on Earth • Important for Astronomy • Only star that we can see closely • The source of many interesting and important physics problems • For Me? • Many basic properties are a mystery! • dynamo, coronal heating, source of high-energy particles, etc. • Space radiation environment, space weather, acceleration of high-energy charged particles Introduction to the Sun 6/17/06

7. Introduction to the Sun 6/17/06

8. Source of the Sun’s Internal Energy:p-p chain is dominate for the Sun; also CNO chain Introduction to the Sun 6/17/06

9. Solar Structure: The Standard Solar Model • Theoretical model used to determine the physical properties of the Sun’s interior • Hydrostatic and thermal equilibrium • A big ball of gas held together by gravity + radiative diffusion • Can add convection, but this is difficult (simple approach – mixing-length theory) • Nuclear reaction rates and opacities are needed • Boundary conditions are tricky – need to use an iterative approach Introduction to the Sun 6/17/06

10. Solar Oscillations • Waves can propagate through the Sun causing a variety of vibrations • Like sound waves • These are used to infer pressures, densities, chemical compositions, and rotation rates within the Sun • Constraints on solar models • Helioseismology Introduction to the Sun 6/17/06

11. Turbulent convective motions cause overturning (bubbling) motions inside the Sun. • These are responsible for the granulation pattern seen on the Sun’s surface. • Rayleigh-Bénard convection Introduction to the Sun 6/17/06

12. Recent High-resolution Images of granulation Introduction to the Sun 6/17/06

13. The photosphere • About 5700K • Coolest region of the Sun (coldest in sunspots) • Sunspots (usually in pairs) • Variety of convection cells (granulation, supergranulation, etc.) • Limb Darkening Introduction to the Sun 6/17/06

14. Introduction to the Sun 6/17/06

15. Introduction to the Sun 6/17/06

16. Introduction to the Sun 6/17/06

17. The Chromosphere • Above the photosphere is a layer of less dense but higher temperature gases called the chromosphere “Color Sphere” • characterized by spikesof rising gas • Spicules extend upward from the photosphere into the chromosphere along the boundaries of supergranules Introduction to the Sun 6/17/06

18. Introduction to the Sun 6/17/06

19. The Corona • The outermost layer of the solar atmosphere, the corona, is made of very high-temperature gases at extremely low density • The solar corona blends into the solar wind at great distances from the Sun • Because the corona is very hot, it is best viewed in the x-ray part of the spectrum • What heats the corona remains an open question! Introduction to the Sun 6/17/06

20. Emission Spectra in the UV Dupree et al., ApJ, 1973 Far UV To the far right of this plot is the extreme UV (soft X-ray) Near UV Introduction to the Sun 6/17/06

21. SOHO/EIT image at 195 Angstroms (FeXII) Introduction to the Sun 6/17/06

22. Sunspots • Existence known since 350 BC (Greece), 28 BC (China) • Lower temperature • Umbra and penumbra • Associated with Intense magnetic fields • Zeeman effect Introduction to the Sun 6/17/06

23. The Babcock model andSolar Dynamo Introduction to the Sun 6/17/06

24. The 11-year Sunspot Cycle Number of Sunspots versus time – they come and go every 11 years Number of Sunspots versus latitude – forms a “butterfly pattern” Introduction to the Sun 6/17/06

25. The Sun and Earth’s Climate:The Maunder Minimum • Complete absence of sunspots for 50 years corresponds to a mini ice age • There is a loose correlation between global man temperature and sunspots Introduction to the Sun 6/17/06

26. Magnetism is the Key to Understanding the Sun Introduction to the Sun 6/17/06

27. Introduction to the Sun 6/17/06

28. Coronal loops expand from the surface of the Sun following a solar explosion (solar flare) on April 21, 2002 TRACE movie Introduction to the Sun 6/17/06

29. The Buildup and release of magnetic field energy Halloween 2003 storms • CMEs and Flares • A solar flare is a brief eruption of hot, ionized gases from a sunspot group • A coronal mass ejection (CME) is much larger • Geomagnetic storms • High-Energy Particles (Space Radiation) Introduction to the Sun 6/17/06

30. The Sun is the Most Important Particle Accelerator in the Solar System Introduction to the Sun 6/17/06

31. Introduction to the Sun 6/17/06

32. Aurora in Tucson Introduction to the Sun 6/17/06

33. SOHO/LASCO (C3) Coronagraph“Halloween” solar storms of 2003 Introduction to the Sun 6/17/06

34. Propagating Shocks • Analogy with sonic booms • Efficient particle accelerators • Radiation Environment and Space Weather Introduction to the Sun 6/17/06

35. My research has shown that the angle between the shock propagation direction and the magnetic field determines the maximum energy in the particle events Perpendicular shocks  high-energy particles Introduction to the Sun 6/17/06

36. Perpendicular Shocks in the solar atmosphere Introduction to the Sun 6/17/06

37. Analogy to Cosmic Rays and Supernove remants:Supernova Remnant 1006 – Chandra image Introduction to the Sun 6/17/06

38. To Finish Introduction to the Sun 6/17/06