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www.iaus247.org. LOC contact: Cesar Mendoza-Briceno (Venezuela). SOC contact: Robertus Erd élyi (UK). The structure of the lower solar atmosphere. Robert Erdélyi Robertus@sheffield.ac.uk SPARC, Department of Applied Mathematics, The University of Sheffield (UK)

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iaus247

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  1. University of Sheffield

  2. www.iaus247.org LOC contact: Cesar Mendoza-Briceno (Venezuela) SOC contact: Robertus Erdélyi (UK) University of Sheffield

  3. The structure of the lower solar atmosphere Robert Erdélyi Robertus@sheffield.ac.uk SPARC, Department of Applied Mathematics, The University of Sheffield (UK) http://robertus.staff.shef.ac.uk University of Sheffield

  4. Lower atmosphere • Photosphere – chromosphere – TR (– corona are)magnetically coupled. • Very highly structured and dynamic; challenge for magnetic seismology via inversion • Three outstanding topics: • Atmospheric/coronal heating. • Influence of magnetic atmosphere, i.e. magnetic carpet, on oscillations. • Role of p modes in the dynamics of the lower atmosphere!(Not yet explored.) University of Sheffield

  5. Wavelength T (C) Visible 5000 Magnetic Field 5000 UV 1600 A 8000 Hydrogen Ha 15,000 Helium EUV 50,000 Iron 8/9 EUV 1 million Iron 11 EUV 1.5 million Lower atmosphere: coupling University of Sheffield

  6. Lower atmosphere • Photosphere – chromosphere – TR (– corona are)magnetically coupled. • Very highly structured and dynamic; challenge for magnetic seismology via inversion • Three outstanding topics: • Atmospheric/coronal heating. • Influence of magnetic atmosphere, i.e. magnetic carpet, on oscillations. • Role of p modes in the dynamics of the lower atmosphere!(Not yet explored.) University of Sheffield

  7. Lower atmosphere University of Sheffield

  8. Lower atmosphere • Photosphere – chromosphere – TR (– corona are)magnetically coupled. • Very highly structured and dynamic; challenge for magnetic seismology via inversion • Three outstanding topics: • Atmospheric/coronal heating. • Influence of magnetic atmosphere, i.e. magnetic carpet, on oscillations. • Role of p modes in the dynamics of the lower atmosphere!(Not yet explored.) University of Sheffield

  9. Lower atmospheric seismology • What is the motivation? • Understand atmospheric structures (spicules, prominences, loops, plumes, etc.) • Source of atmospheric heating; solar wind/particle acceleration Wave properties (speed, amplitude, spectrum) spectroscopic Atmospheric diagnostic parameters (temperature, density) Observations Geometric properties of waveguides (structuring, shape, curvature) imaging Atmospheric physical parameters (B, fine structure, transport coefficients) Coronal (Roberts et al. 1984) /Atmospheric seismology(Erdélyi 2006) University of Sheffield

  10. Objects: atmospheric oscillations Oscillations ubiquitous in Sun • Solar atmosphere • More local oscillations • Sunspot oscillations, prominence oscillations, coronal loop oscillations, plume oscillations • Moreton & EIT waves • Solar interior • Global oscillations • p/f/g-modes • Unifying feature of variety of solar atmospheric oscillations • Waveguide concept • MHD description University of Sheffield

  11. Global oscillations • Red curve: l = 75 • Yellow curve : l = 25 • Green curve: l = 20 • Blue curve: l = 2 • White curve : l = 0 • ν= 3mHz University of Sheffield

  12. Global oscillations • n=14 (radial nodes) • m=16 (poloidal nodes) • l=20 (spherical harmonic degree) • The frequency of this mode determined from the MDI data is 2935.88 0.2 µHz. University of Sheffield

  13. Objects: atmospheric oscillations Oscillations ubiquitous in Sun • Solar atmosphere • More local oscillations • Sunspot oscillations, prominence oscillations, coronal loop oscillations, plume oscillations • Moreton & EIT waves • Solar interior • Global oscillations • p/f/g-modes • Unifying feature of variety of solar atmospheric oscillations • Waveguide concept • MHD description University of Sheffield

  14. Objects: atmospheric oscillations Oscillations ubiquitous in Sun • Solar atmosphere • More local oscillations • Sunspot oscillations, prominence oscillations, coronal loop oscillations, plume oscillations • Moreton & EIT waves • Solar interior • Global oscillations • p/f/g-modes • Unifying feature of variety of solar atmospheric oscillations • Waveguide concept • MHD description University of Sheffield

  15. Sunspot oscillations University of Sheffield

  16. Objects: atmospheric oscillations Oscillations ubiquitous in Sun • Solar atmosphere • More local oscillations • Sunspot oscillations, prominence oscillations, coronal loop oscillations, plume oscillations • Moreton & EIT waves • Solar interior • Global oscillations • p/f/g-modes • Unifying feature of variety of solar atmospheric oscillations • Waveguide concept • MHD description University of Sheffield

  17. Standing kink (transversal) modes • TRACE:Loop oscillation excited by M4.6 flare (14 July 1998) Movie in TRACE 171 A Occurrence rate: 17/255 flares with transverse oscillation Schrijver et al. 2002 University of Sheffield

  18. Objects: atmospheric oscillations Oscillations ubiquitous in Sun • Solar atmosphere • More local oscillations • Sunspot oscillations, prominence oscillations, coronal loop oscillations, plume oscillations • Moreton & EIT waves • Solar interior • Global oscillations • p/f/g-modes • Unifying feature of variety of solar atmospheric oscillations • Waveguide concept • MHD description University of Sheffield

  19. Moreton and EIT waves Moreton waves • Seen in H in the chromosphere at 10000 K (Moreton ’60) • Propagation speeds 450-2000 km/s, away from a flare site • Propagate almost isotropically; confined to an arc rarely exceeding 120º • Have been identified as the intersection of coronal shock waves (due to a flare) with the chromosphere (Uchida ‘68; ‘74) • Are not seen to decelerate • The generation mechanism has not been made clear yet University of Sheffield

  20. Moreton and EIT waves University of Sheffield

  21. Moreton and EIT waves University of Sheffield

  22. Moreton and EIT waves • Moreton waves on difference images after solar eruption University of Sheffield

  23. Objects: atmospheric oscillations Oscillations ubiquitous in Sun • Solar atmosphere • More local oscillations • Sunspot oscillations, prominence oscillations, coronal loop oscillations, plume oscillations • Moreton & EIT waves • Solar interior • Global oscillations • p/f/g-modes • Unifying feature of variety of solar atmospheric oscillations • Waveguide concept • MHD description University of Sheffield

  24. Atmospheric oscillations Oscillations ubiquitous in Sun • Low atmosphere • Ph, Ch, possibly TR • Isolated flux tubes • Effect of stratification • Higher atmosphere • TR, Corona • Magnetic environment vA vA Stratification leads to the Klein-Gordon effect (Roberts 1981, Rae & Roberts 1982, Erdélyi(2005) (Review: Erdélyi, Roberts, Ruderman, Thompson 2006; Erdélyi 2006) University of Sheffield

  25. The Klein-Gordon waves Stratified atmosphere (g=const) • Equilibrium: • Scale height: • 1D, sound waves: • Introduce Webb & Roberts, Sol. Phys, 56, 5 (1978); Ulmschneider and co’s, may papers in A&A; Review by Roberts (2003); Erdélyi & Hargreaves (2005)Erdélyi (2006); De Pontieu & Erdélyi (2006) University of Sheffield

  26. The Klein-Gordon waves Isothermal atmosphere (acoustic cut-off frequency) Photosphere: νac= 4.8 mHz  P = 210 s Corona: νac= 0.18 mHz  P = 91.7 min • Leakage of photospheric motion into LA • Sound, slow, Alfvén waves • γ=5/3  1 • Non-adiabatic plasma • Inclination of magnetic wave guides De Pontieu, Erdélyi & James (2004); De Pontieu, Erdélyi & De Moortel (2005); De Pontieu & Erdélyi (2006) University of Sheffield

  27. Coupling scales and elements Manifestations of presence of solar atmosphere: Organised flows (meridional; differential rotation, etc.) • Flow fields Random flows (granulation, convection, etc.) Coherent global fields (e.g. canopy) • Magnetic fields Random fields (magnetic carpet) University of Sheffield

  28. Solar acoustic oscillations • Separated ridges of power predicted: Ulrich (1970), Leibacher & Stein (1971) • Separated ridges of power observed: Deubner (1975) MDI observations University of Sheffield

  29. Differences in sound speed University of Sheffield

  30. Internal structure vs BCs? • EVP with proper BCs • “Surface term” = ALL the atmospheric physics included!! • Inversion should include (magnetic) solar atmosphere University of Sheffield

  31. Problem: “solar cycle effects” • Time dependent ridges of power observed: systematic frequency decrease (0.42 μHz  0.14 μHz) of low spherical (l) degree p-modes from maximum (1980) to minimum (1984) activity (Woodard & Noyes) • Most obvious theoretical candidate for interpretation: magnetic field (Ledoux & Simon 1957; Goossens et al. 1972, 1976; Biront et al. 1982 in stellar context) • (Campbell & Roberts 1989; Evans & Roberts 1990, 1991, 1992; Jain & Roberts 1993, 1994abc; Miles & Roberts 1992; Erdélyi & Taroyan 2000, 2001, 2002a-c, 2005; Erdélyi, Kerekes & Mole 2005; Erdélyi & Pintér 2005; Shelyag, Erdélyi & Thompson 2005; Petrovay, Erdélyi & Thompson 2005 Erdélyi, Taroyan & Barlow 2006, etc. in solar context) University of Sheffield

  32. Problem: frequency differencies • Strong dependence of frequency shifts on the frequency and degree of the mode • Libbrecht & Woodard 1975 University of Sheffield

  33. GONG observations of line-width • Variation of Г with magnetic activity for a single multiplet (l = 50, m = 9) • Magnetic flux (dashed line) • Sunspot number (dotted line) • Komm et al., ApJ, 531, 1094, 2000 University of Sheffield

  34. BiSON observation of line width variation • Changes in LW of low-angular degree p-modes during fall of SC22 • Averaged over 2.6 to 3.6 mHz • 24 3% mean increase in the modal line width from activity minimum to maximum • Chaplin et al., MNRAS, 313, 32, 2000 University of Sheffield

  35. An example: line-widths (GONG) Surface gravity (f) modes Acoustic (p) modes Dziembowski and Goode, ApJ 2005 University of Sheffield

  36. Model Concept Manifestations of coupling scales: Organised flows (meridional; differential rotation, etc.) • Flow fields Random flows (granulation, convection, etc.) Coherent global fields (e.g. canopy) • Magnetic fields Random fields (magnetic carpet) University of Sheffield

  37. Model Concept • Global oscillations influenced by atmosphere • Global modes interact (e.g. resonantly ) with local MHD modes • Dissipation Steady state • Damping of global oscillations University of Sheffield

  38. Model Concept Manifestations of presence of solar atmosphere: University of Sheffield

  39. B(z) g x canopy (h) y z Simple-minded solar model corona chromospheric transitional layer (L) photosphere solar interior University of Sheffield

  40. Eigenmodes University of Sheffield

  41. Frequency spectrum (L=0, B=0) • Role of atmosphere: cut-off frequencies υI and υII University of Sheffield

  42. Eigenmodes (L=0, B=0) University of Sheffield

  43. Frequency spectrum (L0, B=0) • Role of chromospheric transitional layer (L0): chromosphericg-modes • Modes below Brunt-Väisälä frequency g1 Uchida 1965, Thomas et al. 1971, Deubner & Gough 1984, Clark & Clark 1989, Braun & Fan 1998, Pintér et al. 1998 University of Sheffield

  44. Eigenmodes (L0, B=0) g-modes are trapped in the transition layer where ωBV>0 University of Sheffield

  45. Frequency spectrum (L=0, B  0) University of Sheffield

  46. Frequency spectrum (L=0, B  0) University of Sheffield

  47. Frequency spectrum (L=0, B  0) University of Sheffield

  48. Frequency spectrum (L=0, B  0) • Two-layer model • Polytrop interior • Isothermal atmosphere • vA=cst  β=cst (C&R89) • B=cst (E&R90) • No Alvén/slow continua University of Sheffield

  49. eigenmodes leaky modes leaky modes eigenmodes quasi-modes Frequency spectrum (L=0, B  0) University of Sheffield

  50. Eigenmodes (L  0, B  0) University of Sheffield

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