ISSI, October 11-15, 2004 Synthesis of the Solar Spectrum including future plans Peter Fox ([email protected]) HAO/NCAR Work partly funded by NSF/RISE and

ISSI, October 11-15, 2004

Synthesis of the Solar Spectrum including future plans

Peter Fox ([email protected])HAO/NCAR

Work partly funded by NSF/RISE and NASA/SORCE


Outline

Spectral synthesis Accounting for solar activity Spectral variability by wavelength Validation Outstanding questions Current and next steps


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


Definitions wavelength (in nm, unless noted otherwise) - cosine of heliocentric viewing angle (=1 at

disk center, =0 at limb of Sun) Istructure(,) - specific intensity of radiation (aka

radiance) of a particular structure on the solar disk

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


Process flow overview


Solar spectrum synthesis To construct S(,t) or S(t) requires radiances Istructure(,)

or Jstructure() and the weighting factors: several options1. Full disk surface decomposition2. 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) Istructure(,) S(,t) = structures a structure Jstructure() - 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


Solar spectrum calculations Physics-based models (absolute units)

– Istructure(,)=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)


Spectrum Models Proxy models (regression/calibration)

– Single parameter– Multi-parameter

Physics-based models (absolute units)– Flux – F(t) = (1-fF-fs)F

qs+fF FF+fs F

s

– Istructure(,)=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)


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


Intensity structures (PSPT CaIIK)


Quiet Sun, disk center, near limb, 250-1500nm

Plage

Sunspot


Synthetic Spectra - H


Synthetic Spectra - H


Synthetic Spectra – green band


Lyman- model and Lemaire obs


Spectral variability with activity

1998/06/10 - 1722UT and 2200UT


Spectral variability

1998/06/10 - 1722UT



1998/06/10 - 2200UT



1998/06/10 - 2200UT - 1722UT


Validation with observations


Validation with SOLSPEC/SIM


Validation with SOLSPEC/SIM


Validation with SOLSPEC


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


Quiet, medium, active (areas)

00.10.20.30.4

0.50.60.70.80.9

A C E F H P S

Model/Structure

Fractional area

QuietMediumActive



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=180.2 Mg II=.2723, F10=165.5



1998/09/01:2200UT and 1998/09/03:1722UT


1998/09/01 spectra


Disk-averaged two days apart


Cycle variation (active-quiet)


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


1998/06/10 spectra


1998/06/10 spectra


Disk-averaged two days apart


Disk-averaged ten days apart






UV 285-290nm - ATLAS3/SUSIM (full res)


UV 285-290nm - ATLAS3/SUSIM (0.15nm res)


UV 300-310nm - ATLAS3/SUSIM (full res)


UV 300-310nm - ATLAS3/SUSIM (0.15nm res)


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


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


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

Documents

ISSI, October 11-15, 2004 Synthesis of the Solar Spectrum including future plans Peter Fox ([email protected]) HAO/NCAR Work partly funded by NSF/RISE and