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Modeling the UV/EUV and its relevance for PROBA2 observations

Modeling the UV/EUV and its relevance for PROBA2 observations. Margit Haberreiter Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center, Davos, Switzerland and Laboratory for Atmospheric and Space Physics, University of Colorado, USA. EUV spectrum. Wavelengths

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Modeling the UV/EUV and its relevance for PROBA2 observations

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  1. Modeling the UV/EUV and its relevance for PROBA2 observations Margit Haberreiter Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center, Davos, Switzerland and Laboratory for Atmospheric and Space Physics, University of Colorado, USA

  2. EUV spectrum • Wavelengths • UV: 120 – 400 nm • EUV: 10 – 120 nm • Contribution from the • Chromophere • Transition region • Corona

  3. SolarModeling(SolMod – continuation of SRPM) Multi level atoms 373 ions, from H to Ni with ioncharge 25 ~14’000 atomic levels ~170’000 spectral lines Statistical equation is solved to get the level populations Chromosphere and transition region for ioncharge  2: full NLTE (Fontenla et al., 2006; 2007; 2009) plus optically thin transition region lines Spherical symmetry Corona ioncharge >2 optically thin, i.e. collisions and spontaneous emission Line of sight integration accounts for opacity Spherical symmetry

  4. Masks from Precision Solar Photometric Telescope Continuum, 607 nm (PICARD) Disk mask on 2005/9/12 obtained from PSPT data, Mauna Loa, Hawaii http://lasp.colorado.edu/pspt_access/ (R) Sunspot Penumbra (S) Sunspot Umbra (P) Faculae (H) Plage (F) Active network (D) Quiet network (white) (B) Intergranular Cells • Determined by the contrast as a • function of the position on the disk • Only possible with respect to a • normalized quiet Sun intensity Ca II 393.4, FWHM=0.27nm

  5. Faculae Plage Active network Quiet network Intergranular Cells Fontenla et al., 2009, ApJ 707, 482-502

  6. G-Band of CH molecular lines Fontenla et al., 2009, ApJ 707, 482-502

  7. Violet CN Band Fontenla et al., 2009, ApJ 707, 482-502

  8. Components for quiet Sun Fontenla, Curdt, Haberreiter, et al., 2009, ApJ

  9. Modeling the EUVe.g. Fe XV 284 Å

  10. Coronal models • SRPM Models are based on Doschek (1997), ApJ, 476, 903, Singh et al., 1982, J. Astrophys. 3, 249 • Cranmer et al, 2007, ApJS 171, 520

  11. Coronal lines and Bremsstrahlung

  12. Spectrum from Corona, TR and Chromosphere

  13. SPRM calculation versus the EVE spectrum

  14. EVE calibration spectrum versus calculated spectrum Haberreiter and Fontenla, 2009, AIP conference series EVE rocket calibration flight: Chamberlin et al., 2009, GRL

  15. Quiet Sun versus Coronal Hole

  16. Spherical Symmetry Allows the calculation of intensities at and beyond the limb (e.g. Haberreiter et al. 2008) Account for corona over 2 x area of solar disk Important for Limb/eclipse observations Adopted from Mihalas, 1978

  17. Spherical symmetry

  18. Spherical geometry EIT 171 Å

  19. SOHO/EIT images Fe IX 17.1 nm He II 30.4 nm Fe XV 28.4 nm Fe XII 19.5 nm

  20. EIT wavelengths EVE spectrum SRPM calculation

  21. EIT passbands Fe IX 17.1 nm Fe XII 19.5 nm Fe XV 28.4 nm He II 30.4 nm

  22. He II 30.4 nm – high resolution

  23. Optical depth • Fe XV 17.1 nm: • Disk center: max = 0.06 • Limb: (r=1.02): max = 0.63 (~900,000K) • Fe XV 19.5 nm: • Disk center: max = 0.06 • Limb: (r=1.02): max = 0.34 (~1,100,000K) • Fe XV 28.4 nm: • Disk center: max = 0.39 • Limb: (r=1.02): max = 0.88 (~2,000,000K)

  24. LYRA passbands LYRA CH 3: 17-80 nm LYRA CH 4: 6-20 nm

  25. LYRA measure-ments April 2010 Courtesy, Ingolf Dammaschs

  26. LYRA measure-ments May 2010 Courtesy, Ingolf Dammaschs

  27. Understand the daily variations of the UV/EUV • Determine the solar cycle variation of solar activity features (with an emphasis on coronal holes) → create masks similar to PSPT masks • Model the variation of the solar spectrum in the EUV • Is there a long-term trend of the solar spectral irradiance (due to coronal holes)

  28. Questions to address • Understand the spectral variability • Do all the spectral lines behave similarly OR • Increase of line strength of some lines and a decrease of others? • Is a decrease in the EUV responsible for the decrease in TSI for the current minimum

  29. 1. Variability of solar activity features EIT 17.1nm 07/01/2005 EIT 19.5 nm 10/01/2002 EIT 28.4 nm 10/10/2003 EIT 30.4 nm 07/10/2006 coronal holes – quiet Sun – quiet coronal network – active coronal network - hot loop – super hot loop

  30. EIT image analysis • Radial dependence for outer corona • Thresholds based on intenstiy histogram of the EIT images • Maximum value of histogram varies with solar cycle (in particular for 284 Ǻ) • Coronal hole intensity changes with solar cycle – (Barra et al., 2009) → identification of coroanl features not trivial

  31. Area coverage of features Data from Barra et al, 2009

  32. 3. Determine the long-term trend of the solar spectral irradiance The SOHO/SEM measurements indicate a decrease in the EUV by15% Uncertainty ~ 6% Not explained by F10.7 or sunspot number What is the role of coronal holes? Didkovsky et al., 2009

  33. Conclusions • Good agreement between the synthetic spectra and the observed EVE quiet Sun spectrum • An enourmous amount of spectral lines is contained in broader spectral bands • Strong interest in SWAP images for the reconstruction of LYRA observations

  34. Questions?

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