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Helioseismology

Helioseismology. J ørgen Christensen-Dalsgaard Institut for Fysik og Astronomi, Aarhus Universitet Dansk AsteroSeismologisk Center. The Sun. Five-min oscillations: A local phenomenon in the solar atmosphere?. Musman & Rust (1970; Solar Phys. 13, 261). Models: Ulrich (1970):

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Helioseismology

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  1. Helioseismology Jørgen Christensen-Dalsgaard Institut for Fysik og Astronomi, Aarhus Universitet Dansk AsteroSeismologisk Center

  2. The Sun

  3. Five-min oscillations: A local phenomenon in the solar atmosphere? Musman & Rust (1970; Solar Phys. 13, 261)

  4. Models: • Ulrich (1970): • Wolff (1972): • Ando & Osaki (1975): Oscillation modes of the Sun Deubner (1975; Astron. Astrophys. 44, 371)

  5. The start of global helioseismology Grec et al. (1980; Nature 288, 541)

  6. Crucial advantages • Access to modes of degree up to 1000+ • Observations over very extended period (more than 10 years nearly continuously) • Well-determined global parameters

  7. Observed solar modes Frequencies of solar model n = w / 2 p

  8. Rays

  9. Inversion with rays

  10. Observing a Doppler image

  11. VIRGO on SOHO (whole-disk): Data on solar oscillations Observations: MDI on SOHO

  12. Observed frequencies m-averaged frequencies from MDI instrument on SOHO 1000 s error bars

  13. Frequency differences, Sun - model

  14. No settling No settling Including settling The solar internal sound speed Sun - model

  15. The solar internal sound speed Sun - model Basu et al. (1997; MNRAS 292, 243)

  16. Settling Nuclear burning Changes in composition • The evolution of stars is controlled by the changes in their interior composition: • Nuclear reactions • Convective mixing • Molecular diffusion and settling • Circulation and other mixing processes outside convection zones

  17. Including relativistic effects No relativistic effects Relativistic electrons in the Sun Elliot & Kosovichev (1998; ApJ 500, L199)

  18. Neon discovery solves mystery of sun's interiorNASA's Chandra X-ray Observatory survey of nearby sun-like stars suggests there is nearly three times more neon in the sun and local universe than previously believed. If true, this would solve a critical problem with understanding how the sun works.FULL STORY (Spaceflight Now – 14 Aug 2005)

  19. Pijpers, Houdek et al. Z = 0.015 Model S Revision of solar surface abundances Asplund et al. (2004; A&A 417, 751. 2005; astro-ph/0410214 v2): • Improvements: • Non-LTE analysis • 3D atmosphere models • Consistent abundance determinations for a variety of indicators

  20. How do we correct the models? Basu & Antia (2004; ApJ 606 L85): an opacity increase to compensate for lower Z is required Seaton & Badnell (2004; MNRAS 354, 457): recent Opacity Project results do indicate some increase over the OPAL values, but hardly enough Antia & Basu (2005; ApJ 620, L129): could the neon abundance be wrong?

  21. The neon story Ne x 2.5 Bahcall et al. (2005; ApJ, in the press [astro-ph/0502563]) Drake & Testa (2005; Nature 436, 525): X-ray observations of nearby stars indicate such a neon increase

  22. Spherical harmonics

  23. Rotational splitting

  24. Simple rotational splitting

  25. Kernels for rotational splitting

  26. Base of convection zone Tachocline Near solid-body rotation of interior Inferred solar internal rotation Schou et al. (1998; ApJ 505, 390)

  27. Rotation of the solar interior BiSON and LOWL data; Chaplin et al. (1999; MNRAS 308, 405)

  28. Tachocline oscillations ● GONG-RLS ▲MDI-RLS ∆ MDI-OLA See Howe et al. (2000; Science 287, 2456)

  29. Zonal flows Rotation rate - average value at solar minimum Vorontsov et al. (2002; Science 296, 101)

  30. Radial development of zonal flows Howe et al., (ApJ, in the press)

  31. Observed and modelled dynamics 6 1/2 year MDI inversion, enforcing 11-yr periodicity Vorontsov et al. (2002; Science 296, 101) Non-linear mean-field solar dynamo models Covas, Tavakol andMoss (2001; Astron. Astrophys 371, 718)

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