1. An Introduction to Helioseismology (Local) 2008 Solar Physics Summer School June 16-20, Sacramento Peak Observatory, Sunspot, NM

2. Local Helioseismology What is Local helioseismology? –Comparison with Global Helioseismology –History –Why Local Helioseismology Observations for Local Helioseismology The three main methods –Ring diagram analysis –Time Distance –Seismic Holography (seismic imaging) The Space Weather connection

3. Global Modes A p mode is a standing acoustic wave. Each mode can be described by a spherical harmonic. Quantum numbers n (radial order), l (degree), and m (azimuthal order) identify the mode. -l  m  l

4. Approximation to plane waves

5. Global vs Local Global 1.Horizontal interference selects integer values of ℓ 2.Entire sun is sampled 3.Spherical harmonics describe waves 4.Cannot get structure as function of longitude 5.Cannot get non-symmetric latitudinal structure 6.One basic technique 7.Valid for ℓ < ~180 Local 1.No horizontal interference, can have any wavelength 2.Localized volume is sampled 3.Sinusoids or Hankel functions describe waves 4.Longitudinal structure can be determined 5.Non-symmetric latitudinal structure can be determined 6.Several techniques 7.Valid for ℓ > ~180

6. Helioseismology: A window to the Sun’s Interior

7. History 1987: Sunspots are observed to absorb p- modes 1988: Ring diagram method is invented 1990: Acoustic holography is invented 1993: Time-distance method is invented

8. Why local helioseismology ? Infer dynamics and structural parameters of localized areas of the Sun Difference between North and South hemisphere Longitudinal discrimination Meridional circulation Structure and dynamics of active regions and filaments

9. Observations High spatial resolution velocity or intensity images –Current Instruments: GONG MDI on board of SoHO SOT on board of Hinode –Future: HMI on board of SDO PHI on board of Solar Orbiter

10. Networks Six stations around the world for continual coverage. 256x256 pixels 1995- 2001 1024 pixels since 2001 Run from NSO Tucson.

11. Space Instruments 1996 - Present Coming Soon…. MDI GOLF VIRGOHMI

12. Ring Diagram Analysis 1664 min 16 o

13. Ring-Diagrams analysis Rings of Power l- diagram

14. Ring-Diagrams analysis No tracking, solar rotation rate of 2000 m/s With tracking to remove rotation

15. Ring-Diagrams analysis Flow maps

16. Ring-Diagrams analysis Solar Rotation Confirmation of the solar rotation shear layer from local helioseismology

17. Ring-Diagrams analysis Meridional Circulation

18. Ring-Diagrams analysis Meridional Flow: removing surface activity

19. Ring-Diagrams analysis Meridional Flow

20. Ring-Diagrams analysis Dynamics of Active regions

21. AR 10486 AR 10069

22. Ring-Diagrams analysis Helicity and flare production

23. Time distance Sound travels from a particular location, down, and comes back up at some time later and some distance away from the source. The time and distance is influenced by the conditions of the plasma that the wave travels through. More resolution that ring- diagrams. Reach deeper layers

24. Time distance Observed time-distance diagram Cross-correlation function is well described by a Gabor wave packet

25. Turning points

26. Time distance Active regions underlying structure

27. Time distance Meridional Flow 30 Mm 200 Mm 65 Mm 130 Mm

28. Time distance Sunquakes

29. EARTHEARTH Seismic holography (seismic imaging) Egression/Ingression Pupil

30. Seismic holography (seismic imaging) Phase of the Correlation Phase-difference due to: Reduction of gas pressure in magnetic region --> displacement of density variation Sound speed enhancement (evidence from acoustic moats) due to thermal anomalies Inclination of the magnetic field

31. Seismic holography Prediction capability Carrington Longitude sin(latitude) Active Region NOAA-10808 Aug 29  Sep 9 2005 (GONG) AR10808 Sept 7 2005 Source: MLSO K-coronameter

32. Calibrating the far-side maps Carrington Longitude sin(latitude) Active Region NOAA-10808 Aug 29 -> Sep 9 2005 AR10808 Active Region NOAA-10923 Oct 31 -> Nov 10 2006 AR10923 sin(latitude)

33. Calibrating the far-side maps

35. Rings: easy and intuitive; low spatial resolution and shallow depth range TD: harder; higher spatial resolution and greater depth range, but inversions…. Holography: Similar to TD, but needs a good understanding of the Green’s functions. All methods have a trade-off between depth range and spatial resolution Comparison of methods

36. Images of activity in the far side of the Sun Flare prediction Emerging active regions Local helioseismology & Space Weather

37. To Do Huge list!!!! http://www.hao.ucar.edu/summerschool/program.html Has links to very detailed lecture notes on helioseismology and solar internal dynamics For more information