1. ISSI, October 11-15, 2004 Synthesis of the Solar Spectrum including future plans Peter Fox (pfox@ucar.edu) HAO/NCAR Work partly funded by NSF/RISE and NASA/SORCE

2. ISSI, October 11-15, 2004 Outline Spectral synthesis Accounting for solar activity Spectral variability by wavelength Validation Outstanding questions Current and next steps

3. ISSI, October 11-15, 2004 Definitions - ISO DIS 21348 Types (section 5) –1 - measurement set product –2 - reference spectrum product –3 - empirical model product –4 - first principles model product –5 - surrogate (proxy) product Spectral categories (section 6) –Cosmic rays, gamma-rays, X-rays –UV –Visible –IR –Microwave –Radio –Total Irradiance

4. ISSI, October 11-15, 2004 Definitions  wavelength (in nm, unless noted otherwise)  - cosine of heliocentric viewing angle (  =1 at disk center,  =0 at limb of Sun) I structure (,  ) - specific intensity of radiation (aka radiance) of a particular structure on the solar disk n S - solar irradiance s - source function  optical depth Covers UV (part UVC, UVB, NUV, UVA), VIS, IR (NIR, MIR and part FIR) Calculate ‘pseudo’-total irradiance

5. ISSI, October 11-15, 2004 Process flow overview

6. ISSI, October 11-15, 2004 Solar spectrum synthesis To construct S (, t) or S(t) requires radiances I structure (,  ) or J structure ( ) and the weighting factors: several options 1. Full disk surface decomposition 2. Disk averaged weighting using mean disk intensity NB - Variability arises due to changes in surface contributions (in part or whole, depending on timescale) S (, t) =  (structures, disk) I structure (,  ) S(, t) =  structures a structure J structure ( ) - a is the coefficient S(t; 1, 2 ) = Integral ( S(  t) d ) between 1 and 2 S (, t;  1 ) = Integral ( S( ’  t) k( ’) d ’ ) - k is instrument profile,  1 is bandpass/resolution

7. ISSI, October 11-15, 2004 Solar spectrum calculations Physics-based models (absolute units) –I structure (,  )= Integral ( S (  ) exp (-  /  ) d  /  Non-LTE radiative transfer, multi-level atoms, molecules, ionization, continuum and line-by-line, using variable spectral resolution, for any disk position Source function calculations – some PRD, some CRD, some “net radiative bracket” (see Fontenla et al. 1999 for details)

8. ISSI, October 11-15, 2004 Spectrum Models Proxy models (regression/calibration) –Single parameter –Multi-parameter Physics-based models (absolute units) –Flux – F (t) = (1-f F -f s )F qs +f F F F +f s F s –I structure (,  )= Integral ( S (  ) exp (-  /  ) d  /  Non-LTE radiative transfer, multi-level atoms, molecules, ionization, continuum and line-by-line, using variable spectral resolution, for any disk position Source function calculations – some PRD, some CRD, some “net radiative bracket” (see Fontenla et al. 1999 for details)

9. ISSI, October 11-15, 2004 Characterizing solar activity Structures –A – faint cell interior/ network –C – average cell center quiet Sun –E – average network –F – bright network/ faculae –H – average plage –P – bright plage –S – sunspot umbra

10. ISSI, October 11-15, 2004 Intensity structures (PSPT CaIIK)

11. ISSI, October 11-15, 2004 Quiet Sun, disk center, near limb, 250-1500nm Plage Sunspot

12. ISSI, October 11-15, 2004 Synthetic Spectra - H 

13. ISSI, October 11-15, 2004 Synthetic Spectra - H 

14. ISSI, October 11-15, 2004 Synthetic Spectra – green band

15. ISSI, October 11-15, 2004 Lyman-  model and Lemaire obs

16. ISSI, October 11-15, 2004 Spectral variability with activity 1998/06/10 - 1722UT and 2200UT

17. ISSI, October 11-15, 2004 Spectral variability 1998/06/10 - 1722UT

18. ISSI, October 11-15, 2004 Spectral variability 1998/06/10 - 2200UT

19. ISSI, October 11-15, 2004 Spectral variability 1998/06/10 - 2200UT - 1722UT

20. ISSI, October 11-15, 2004 Validation with observations

21. ISSI, October 11-15, 2004 Validation with SOLSPEC/SIM

22. ISSI, October 11-15, 2004 Validation with SOLSPEC/SIM

23. ISSI, October 11-15, 2004 Validation with SOLSPEC

24. ISSI, October 11-15, 2004 Disk-averaged solar activity Mg II index Ca K plage index F10/E10  K /  R (SFO) Use for weighting for spectral irradiance not as a proxy or total

25. ISSI, October 11-15, 2004 Quiet, medium, active (areas)

26. ISSI, October 11-15, 2004 Spectral variability Proxies ~ daily, some extend over many decades Use each proxy as a coefficient for each structure, e.g. Mg II for plage, F10 for spots (3-component model) Require some ‘calibration’, use mean-disk radiances Mg II=.2735, F10=180.2Mg II=.2723, F10=165.5

27. ISSI, October 11-15, 2004 Spectral variability 1998/09/01:2200UT and 1998/09/03:1722UT

28. ISSI, October 11-15, 2004 1998/09/01 spectra

29. ISSI, October 11-15, 2004 Disk-averaged two days apart

30. ISSI, October 11-15, 2004 Cycle variation (active-quiet)

31. ISSI, October 11-15, 2004 Spectral variability - disk-average 1998/06/10 (Mg II=.2711, F10=115.3) 1998/06/12 (Mg II=.2710, F10=115.7) 1998/06/20 (Mg II=.2691, F10=104.4) Solar cycle (active to quiet) Mg II=.2723, F10=165.5

32. ISSI, October 11-15, 2004 1998/06/10 spectra

33. ISSI, October 11-15, 2004 1998/06/10 spectra

34. ISSI, October 11-15, 2004 Disk-averaged two days apart

35. ISSI, October 11-15, 2004 Disk-averaged ten days apart

36. ISSI, October 11-15, 2004 Cycle variation (active-quiet)

37. ISSI, October 11-15, 2004 Cycle variation (active-quiet)

38. ISSI, October 11-15, 2004 UV 285-290nm - ATLAS3/SUSIM (full res)

39. ISSI, October 11-15, 2004 UV 285-290nm - ATLAS3/SUSIM (0.15nm res)

40. ISSI, October 11-15, 2004 UV 300-310nm - ATLAS3/SUSIM (full res)

41. ISSI, October 11-15, 2004 UV 300-310nm - ATLAS3/SUSIM (0.15nm res)

42. ISSI, October 11-15, 2004 Status of physics-based Models Missing some lines, some incorrect gf values – many corrected using NIST data Including free-bound continua of Fe, Ca, K and Na in UV (260-270nm) to solve miss-match with observations Line broadening only includes micro-turbulent velocities Lower population levels now computed in non-LTE Elemental ionization is now computed in non-LTE Approximation to non-LTE source function now includes multi-levels and recombination PRD and CRD

43. ISSI, October 11-15, 2004 Current steps Still adding some missing lines, correcting gf values – many using NIST data, stark broadening Molecules being added as data becomes available (350-400nm) both line and continuum Decomposition algorithm for solar images is being refined to accommodate seeing changes and exposure time differences

44. ISSI, October 11-15, 2004 Future plans Much work to be done interpreting the observed lower resolution variability in the context of higher resolution models and effect on redundancy Use full-disk vector magnetic field measurements from SOLIS to develop next set of atmospheric models AND for surface decomposition Fractional masks? Comparison between other intensity-based synthesis models Radiance observations in the nearIR to refine F and P models (and H) Improve S model Document improvements/changes in synthesis process and ensure ISO compliance