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Atmospheric seismology with SDO: theory viewpoint

This article explores the theory behind atmospheric and coronal seismology using SDO observations. It discusses the challenges, tools, and software needed to fully understand the oscillations in the Sun's atmosphere. The article also examines the different types of waveguides and the manifestations of the solar atmosphere.

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Atmospheric seismology with SDO: theory viewpoint

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  1. Atmospheric seismology with SDO: theory viewpoint R. Erdélyi & B. De Pontieu 1robertus@sheffield.ac.uk, 2bdp@lmsal.com 1SPARG, Department of Applied Mathematics, The University of Sheffield (UK); LMSAL, Palo Alto (USA) http://www.shef.ac.uk/~robertus University of Sheffield

  2. He EUV 50,000 K Fe VIII/IX EUV 1 MK Recap… • Two basic facts: • Photosphere – chromosphere – TR – corona aremagnetically coupled. • Very highly structured and dynamic X rays 4-6 MK Fe XIV 3 MK Magnetic field 5000 K Fe XI 1.5 MK Credit: www.lmsal/com Hα 15,000K UV 1600 Å 8000 K University of Sheffield

  3. Recap… • Two basic facts: • Photosphere – chromosphere – TR – corona aremagnetically coupled. • Very highly structured and dynamic • Is this environment not too hostile doing atmospheric/coronal seismology (A/CS)? • Yes, it is! University of Sheffield

  4. Recap… • Two basic facts: • Photosphere – chromosphere – TR – corona aremagnetically coupled. • Very highly structured and dynamic • Is this environment not too hostile doing atmospheric/coronal seismology (A/CS)? • Yes, it is! • So, can we actually do A/CS? • Not really! At least not in the strict sense of definition of seismology, but… University of Sheffield

  5. Some fundamental Q’s… • A few basic Q’s as far as AIA/SDO is concerned: • What is needed to get the full potential of AIA out for A/CS? • What do we not understand yet? • Where are the stumbling blocks to get full seismological data about the corona? • What kinds of tools need to be developed? • What kind of software? University of Sheffield

  6. 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

  7. Objects: atmospheric oscillations Oscillations ubiquitous in Sun • Solar atmosphere • Numerous resonators • Practically 1-2 modes • Solar interior • One resonator • Numerous modes • However, good news for atmosphere • Standing + progressive waves University of Sheffield

  8. Atmospheric oscillations Another difficulty: different types of waveguides • 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

  9. Seismic scales and elements Waveguides in solar atmosphere: Organised flows (steady loops) • Flow fields Random flows (energy bursts-driven flows: RA, MRC) Coherent fields (loops, arcades) • Magnetic fields Random fields (threads, fine struct’s) University of Sheffield

  10. Joint AIA-MHI seismology 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

  11. Two examples • Manifestation of coupling has some exciting & promising aspects: • Influence of magnetic atmosphere, e.g. magnetic carpet, on oscillations. • Role of photospheric motions (e.g. p modes) in the dynamics of the solar atmosphere! University of Sheffield

  12. Example 1: line-widths (GONG) Surface gravity (f) modes Acoustic (p) modes Dziembowski and Goode, ApJ 2005 University of Sheffield

  13. B(z) g x canopy (h) y z Ex 1: Simple-minded modelling corona chromospheric transitional layer (L) photosphere solar interior University of Sheffield

  14. Ex 1: Eigenmodes (L  0, B  0) University of Sheffield

  15. Ex 1: Eigenmodes (L  0, B  0) • Three-layer model • Polytrop interior • Magnetic transitional layer resonances damping • Isothermal magnetic upper atmosphere • Presence of Alvén/slow continua • Tirry et al. 1998, Pintér et al. 1999 University of Sheffield

  16. p8 l = 100 L = 2Mm Δν (μHz) p4 f p1 p2 p3 Imν (nHz) Bc (G) l = 100 L = 2Mm Bc (G) Ex 1: Eigenmodes (L  0, B  0) • Erdélyi and Pintér 2005 University of Sheffield

  17. Ex 1: Eigenmodes (L  0, B  0) Direction of B • Erdélyi, Pintér & Goossens 2006 University of Sheffield

  18. Dowdy et al. (1986) Solar Phys., 105, 35 Modelling improvement Gabriel (1976), Phil. Trans. A281, 339 University of Sheffield

  19. Possible challenges… • De Pontieu, Tarbell & Erdélyi 2003 University of Sheffield

  20. Ex 2a: The Klein-Gordon waves Stratified atmosphere (g=const) • Equilibrium: • Scale height: • 1D, sound waves: • Introduce Progressive atmospheric waves Webb & Roberts, Sol. Phys, 56, 5 (1978) Ulmschneider and co’s, many papers in A&A Erdélyi & Hargreaves (2006) Reviews by Roberts (2003), Erdélyi (2006) University of Sheffield

  21. Ex 2a: 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 • AIA: 2-10 s resolution => Theory needed • Non-equilibrium MHD simulations • 2-3D MHD Erdélyi & James (2004); De Pontieu et al. (2004) University of Sheffield

  22. Ex 2a: The Klein-Gordon waves • AIA’s 2-10 s time resolution • Not just sound/slow but Alfvén modes to be considered • AIA’s wide temperature coverage • Allows tracing from 0.8 MK to few MK • Theory also needs to address • Dissipative effects • Twisted tubes • Tube fine structure • Closed tubes  standing waves University of Sheffield

  23. Example 2b: Leakage of photospheric motions into the solar atmosphere:driving atmospheric dynamics (spicules and coronal waves) University of Sheffield

  24. Earth Peter & von der Lühe (1999) Earth Ex 2b: Dynamics - Solar spicules University of Sheffield

  25. Ex 2b: LA moss oscillations Oscillations usually suddenly start and stop. Not steady waves but wave trains of finite duration. Oscillations usually last for 32±7 mins or 3 to 7 cycles (just like p-modes): rarely continue for more than 40 min. University of Sheffield

  26. Ex 2b: P-mode driven spicules (and coronal oscillations) Vertical flux tube Inclined flux tube (50°) Chromospheric dynamics in inclined flux tubes are dominated by five minute periods because of significantly increased leakage of photospheric p-modes into the atmosphere University of Sheffield

  27. Ex 2b: P-mode driven spicules (and coronal oscillations) The match between predicted spicule occurrence and observed spicule occurrence is good, especially considering the limitations of the numerical model  = 50° University of Sheffield

  28. Atmospheric oscillations SOHO/TRACE examples (mainly TR and higher) • Two types of observed oscillations can be distinguished • Propagating waves (Ofman et al. 1997, DeForest & Gurman 1998, Berghmans & Clette 1999, De Moortel et al. 2000, 2002a,b,c, Robbrecht et al. 2001, King et al. 2003, Marsh et al. 2003) • Standing waves i) Standing kink-mode oscillations by TRACE (Aschwanden et al. 1999, 2002, Nakariakov et al. 1999, Schrijver & Brown 2000, Schrijver et al. 2002, ) ii) Standing slow-mode oscillations by SOHO/SUMER (Kliem et al. 2002; Wang et al. 2002, 2003a,b) Reviews by Aschwanden (2003), Wang (2004) University of Sheffield

  29. TRACE 171 Å Ex 2b: P-mode driven (spicules) and coronal oscillations From De Moortel et al. (2002) Many observations of intensity oscillations in TRACE 171 Å loops, identified as propagating MAW in 1 MK plasma. University of Sheffield

  30. Wavelet power for observations Intensity oscillations from observations Wavelet power for simulations rebinned to emulate resolution of data (30 s, 2 arcsec) Intensity oscillations from simulations (rebinned to emulate resolution of data) Ex 2b: P-mode driven (spicules) and coronal oscillations University of Sheffield

  31. P-mode driven spicules: 2-D University of Sheffield

  32. Summary • Numerous examples of waves & osc’s in solar atmosphere structures • MHD theory: satisfactory description, but improvements are badly needed (fine structures, radiation issues) • Atmospheric seismology provides us information about: magnetic field, transport coefficients, fine structures, etc. • Joint AIA-HMI seismology: e.g. photospheric motions (p-modes, granular, etc.) leak to atmosphere & atmosphere has back-reaction on global oscillations • Stratification needs to be addressed in theory University of Sheffield

  33. The end University of Sheffield

  34. Summary • De Pontieu, Tarbell & Erdélyi, ApJ, 590, 502 (2003) University of Sheffield

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