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Modelling the Solar UV variability

This study conducted by Margit Haberreiter from PMOD/WRC in Davos, Switzerland, delves into modeling the solar ultraviolet (UV) variability. It covers synthetic spectra, magnetic flux identification in active regions from magnetograms, and spectral variability modeling using COSI. The research also looks into temperature profiles and emission due to LTE and NLTE. Issues encountered in the calculations of spectra are discussed, along with comparisons with measurements and synthetic models. The study aims to address the daily variability of Lyman α and the annual mean spectral variability, exploring factors influencing UV variability. The future directions include refining reconstructions based on different model atmospheres and magnetic analyses.

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Modelling the Solar UV variability

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  1. Modelling the Solar UV variability M. Haberreiter ISSI Study Team on Solar Magnetism and Irradiance 11.-15.October 2004 Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  2. Overview • Synthetic spectra • Reconstruction • Conclusions • What’s next Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  3. Identification of active regions from magnetograms 1. Magnetic flux  filling factor  2. Intensity contrast < 1 sunspot (umbra, penumbra) else  faculae th: threshold magnetic flux 3: magnetic fluxsaturation Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  4. Modeling spectral variability Intensity spectra calculated with COSI: • quiet sun, Model C • faculae, Model P • sunspots, Model S Magnetogram analysis: • time-dependent filling factorsfor faculae (+network) ,sunspots Variation of solar activity: Krivova & Solanki (2003) Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  5. COSI - COde for Solar Irradiance • Updated version of the spherical radiative transfer code based on Schmutz W., 1997, A&A, 321, 268 • Spectrum synthesis program SYNSPEC, based on Hubeny 1988, Hubeny & Lanz 2000 • Physics-based model • atmosphere structure (p, T) by Fontenla et al., ApJ, 1999 for quiet Sun, sunspots, faculae • spherical geometry Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  6. COSI – COde for Solar Irradiance • non-local thermodynamic equilibrium (non-LTE), important below 200 nm • non-LTE line blanketing with opacity distribution functions • Latest photoionization cross sections • C I, Mg I, Al I, Si I, Fe I (Haberreiter et al. 2002) • Opacity project (Seaton et al. 1994) • IRON project (Bautista & Pradhan 1997) Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  7. Temperature profiles Fontenla et al. 1999, ApJ Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  8. Emission due to LTE and rising temperature H I  4863 - LTE Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  9. H I  4863 - NLTE Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  10. Hydrogen lines Haberreiter & Schmutz, 2003 Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  11. Model P - plage Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  12. Model C – quiet Sun Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  13. Model S - sunspot Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  14. Problems in the calculations of the spectra • Missing opacity in the UV • improvement with the new line list  • Problems of the continuums opacity • Inconsistency in the • Validation of Hminus bound free and free free opacity • Validation of the line formation of some lines Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  15. COSI versus measurement Data: Burlov-Vasiljev et al. 1995 Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  16. Synthetic spectrum versus Thuillier Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  17. Comparison of linelists • 200 to 325 nm more lines in new line list • additional opacity Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  18. Continuum-test Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  19. Magnetogram Data Begin End • NSO/Kitt Peak Vacuum Telescope, Tucson • NSO/KP, 512nm 08 / 24 / 1974 04 / 07 / 1992 • NASA/NSO, 868nm 11 / 21 / 1992 12 / 22 / 2001 (05 / 18 / 1996) • MDI/SOHO 05 / 19 / 1996 04 / 17 / 2002 MDI: Michelson Doppler Imager Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  20. Reconstruction quiet Sun Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  21. Daily Variability of Lyman  Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  22. Spectral variability – annual mean Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  23. Spectral variability – annual mean Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  24. Why is the variability too low? • free parameter sat is fitted to give the best correlations to the TSI composite • Considerable effect on TSI • Effect of sat on the UV? • Different sat for different model atmospheres? Thomas Wenzler et al. 2004 Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  25. Lyman – KP SPM Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  26. =320 nm– KP SPM Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  27. Conclusions • The Lyman reconstruction is lower than SOLSTICE data and Wood's composite but not so bad for the SUSIM data • Reconstructed UV variability is considerably lower than the SUSIM data or the Lean reconstruction • Is the free parameter of the magnetogram analysis different for different model atmospheres? • If yes, the freeparameter has to be determined for the model atmospheres by Fontenla Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  28. What’s next • Basis for the reconstruction • OLD: Faculae, quiet Sun and sunspots • NEW: umbra and penumbra instead of a single sunspot model (Alexandra Tritschler, 2002) • Latest version of the magnetogram-analysis (Wenzler 2004a,b) • Comparison with other synthetic models and reconstructions • P. Fox, Ilaria Ermolli on the basis of PSPT images • Implement the depth dependent turbulence broadening Margit Haberreiter, PMOD/WRC, Davos, Switzerland

  29. Thank you! Margit Haberreiter, PMOD/WRC, Davos, Switzerland

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