Solar Radiation Physical Modeling and Solar Spectral Irradiance
J. Fontenla
LASP-Univ. of Colorado
2006/9/10
Juan.Fontenla@lasp.colorado.edu
1

Spectral Solar Irradiance Data
Space Measurements
(UARS, SUSIM, SOLSPEC, SORCE, etc)
Theoretical
Interior Models
Ground Based Measurements
(Labs & Neckel, Wallace et al., etc)
Semi-Empirical
Atmospheric Models
| Solar Radiation Physical Modeling (SRPM) |
Seeks not to replace these, but rather to integrate them in a consistent physical model that matches the observations.
2

Incident (TOA) and Absorbed
Flux Spectrum
F abs
= ( 1 −
T
)
F
0
3

Accumulated flux spectrum, incident and absorbed
F accum
( )
=
λ
F
( ) d
λ
λ
0
∫ ' 4

Carbon Ionization and Mass FLow
......... Static case (w/dif)
_____ Upflow case (w/dif)
0.4
0.2
0.8
0.6
0.0
10
4
2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9
10
6 n lev
,n ion
,…(x,y,z,t) Intermediate
Parameters
I( λ , μ , φ ,t)
Physical Models
& Processes
T,ne,nh,U,...(x,y,z,t) I( λ , μ , φ ,t) 5

Emitted Spectra Radiative Losses
Mean Intensity and Net Radiative
Brackett
Atomic
Data
Atomic
Continua
Atomic
Lines
Radiative Transfer
Non-LTE
Molecular
Continua
Molecular
Lines
Molecular
Data
Populations &
Ionization
Populations &
Ionization
Balance
Momentum &
Energy
Balance
Atmospheric
Parameters
6

SRPM spectrum at 10 disk positions computed with dynamic resolution
Δλ =0.02 nm
λ / Δλ =10 5
λ / Δλ =10 6
Each wavelength is computed using the monochromatic radiative transfer equation.
7

8

9

Populations Departure from LTE
10

11

Matching Disk-Center Spectrum
From Radio to UV
12

Irradiance & Features on the Sun
PSPT red band image
PSPT Ca II K image
13

20 April 2005
Solar Longitude
14

Quiet-Sun Irradiance Spectrum
6600
6400
6200
6000
5800
5600
5400
SIM
SOLSPEC
SRP M C304
5200
5000 1
.
10
4
1.5
.
10
4
2
.
10
4
2.5
.
10
4
W avenumber (cm^-1 )
The spectra for each feature and disk position is convolved (degraded) at any desired resolution, and then combined to form the irradiance.
3
.
10
4
15

• Full-resolution, complete coverage (1nm-
10 μ m), solar irradiance reference spectrum
– representative of quiet-Sun, well documented
• Variability spectrum at full-resolution for any observed distribution of solar activity
– for any given mask of observed solar activity
• Understand sources on the Sun of the fullresolution variability spectrum
– physical understanding that allows extrapolation
16

• Improve visible & IR continuum and lines :
– Tune the model photospheres if warranted
– Keep updating the atomic data (NIST V3.0)
– Extend non-LTE to more species (e.g. Mg, Fe )
• Extend SRPM to the UV (100-400 nm) :
– Improve chromosphere and transition region from model C305
– Develop improved magnetic features chromospheres
– Run non-LTE for all relevant species
• Extend SRPM to the EUV ( λ <100 nm) :
– Develop model corona & use coronal images
– Consider more ionization stages
– Use more recent observations of spectra and variability
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• Fontenla, J., & Harder, J., “Physical Models of Spectral Irradiance Variations”,
MmSAI , 76, 826-833 (2005)
• Harder, J., Fontenla, J., White, O., Rottman, G., & Woods, T., “Solar Spectral
Irradiance Variability Comparisons of the SORCE SIM Instrument with
Monitors of Solar Acitivity and Spectral Synthesis”, MmSAI , 76, 735-742
(2005)
• Fontenla, J.M., Avrett, E., Thuillier, G., & Harder, J., “Radiation-Effective Solar
Atmosphere Models. I. Quiet and Active-Sun Photosphere”, ApJ, 639 , 441-458
(2005)
• Fontenla, J.M., Harder, J., Rottman, G., Woods, T.N., Lawrence, D.M., &
Davis, S., "The Signature of Solar Activity in the Infrared Spectral Irradiance",
ApJ, 605 , L85-L88 (2004)
• Fontenla, J.M., Avrett, E.H., & Loeser, R., "The Energy Balance in the Solar
Transition Region. IV. Hydrogen and Helium Mass Flows with Diffusion", ApJ,
572 , 636-662 (2002)
• White, O.R., Fontenla, J.M., & Fox, P., "Extreme Solar Cycle Variability in
Strong Lines Between 200 and 400 nm", Sp. Sci. Rev., 94 , 67-74 (2000)
• Fontenla, J.M., White, O.R., Fox, P.A., Avrett, E.H., & Kurucz, R.L.,
"Calculation of Solar Irradiances I: Synthesis of the Solar Spectrum", ApJ, 518 ,
480-499 (1999)
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