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An Introduction to Helioseismology (Local)

An Introduction to Helioseismology (Local). 2008 Solar Physics Summer School June 16-20, Sacramento Peak Observatory, Sunspot, NM. Local Helioseismology. What is Local helioseismology? Comparison with Global Helioseismology History Why Local Helioseismology

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An Introduction to Helioseismology (Local)

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

  12. 1664 min 16o Ring Diagram Analysis

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

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

  15. Ring-Diagrams analysisFlow maps

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

  17. Ring-Diagrams analysisMeridional Circulation

  18. Ring-Diagrams analysisMeridional Flow: removing surface activity

  19. Ring-Diagrams analysisMeridional Flow

  20. Ring-Diagrams analysisDynamics of Active regions

  21. Ring-Diagrams analysisDynamics of Active regions AR 10069 AR 10486

  22. Ring-Diagrams analysisHelicity 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 distanceActive regions underlying structure

  27. Time distanceMeridional Flow 30 Mm 65 Mm 130 Mm 200 Mm

  28. Time distanceSunquakes

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

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

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

  33. Calibrating the far-side maps

  34. Calibrating the far-side maps

  35. Comparison of methods • 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

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

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

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