Section 1
Solar Radiance Synthesis Code
Version 1 - 1994 - 2001
Objectives:
• Produce code to compute, in a first approximation, the visible spectral
radiance for any given 1-dimensional solar-type atmospheric models.
• Validate a standard set of atmospheric models for different lowresolution solar features, and compare the intensities computed for
each feature with available observations.
• Understand the role of features observed on the solar surface and solar
magnetic activity in determining the solar irradiance at the Earth.
Methods:
¾ Portable C++ Object Oriented code developed to run in Windows or
Unix for production and using NETCDF files format.
Spectra Data
File
Continuum
Opacity
Radiation
Spectral
Lines
H
Populations
Atmospheric
Models File
Elemental
Ionizations
¾ The FAL set of seven atmospheric models based on a temperature vs.
height deduced from many published observations:
9 A, C, E quiet Sun supergranulation;
9 F enhanced network;
9 H weak plage, P bright plage;
9 S sunspot umbrae.
¾ Include the main species for the visible spectra and the full Kurucz
CD list of atomic lines. Computing all species but H and H- in LTE
for the ionization and level populations, except that for strong lines an
approximate method for non-LTE is used.
Version 1 Limitations:
¾ Have not included a penumbrae model, which underestimates the
effects of sunspots.
¾ Have not included detailed non-LTE effects in the spectrum
calculations (except in H), so that the centers of strong lines,
particularly below 400 nm, are only approximate.
¾ Did not include molecules other than H2+, which doesn’t allow
proper computations above 1 micron and in certain bands (e.g.,
around 410 nm).
Achievements:
¾ Calculated values are in good agreement with the available
observations in the range 400 nm to 1 micron, except for a gap around
410 nm.
¾ The calculated high-resolution spectrum with single lines and blends
of many lines identified is highly useful in interpreting observed
spectra having insufficient spectral resolution to distinguish between
the components of line blends.
¾ Helps interpret the absolute measurements of solar irradiance that
cannot resolve the many thousands of lines that crowd the solar
spectra.
¾ Combining the spectral and total irradiance calculated from a given
plage, sunspot, and active network distribution over the disk provides
a much better understanding of the effects of such features than is
possible from indirect inferences using observed irradiances alone.
Comparison of results with SOLSPEC and Wherli web page data:
A small piece of the full resolution synthesis spectra:
2.5
Irradiance (W/m^2/nm)
2
1.5
1
0.5
0
510
511
512
513
514
515
516
Wavelength (nm)
517
518
519
520
The spectra at 1 nm resolution:
(Note: The instrument profiles are somewhat different between all these
spectra so the details may not match exactly.)
Irradiance at 1 AU (W/m^2)
2
1.5
1
400
500
Synthesis V1
Wherli site
SOLSPEC
600
700
Wavelength (nm)
800
900
1000
6100
Brightness Temperature at 1 AU (K)
6000
5900
5800
5700
5600
5500
400
500
Synthesis V1
Wherli site
SOLSPEC
600
700
Wavelength (nm)
800
900
1000
The spectra at SIM resolution:
Irradiance at 1 AU (W/m^2)
2
1.5
1
400
500
600
700
Wavelength (nm)
800
900
1000
600
700
Wavelength (nm)
800
900
1000
Synthesis V1
SOLSPEC
SORCE (SIM ESR)
6100
Brightness Temperature at 1 AU (K)
6000
5900
5800
5700
5600
5500
400
500
Synthesis V1
SOLSPEC
SORCE (SIM ESR)
Comparison of the spectral irradiance variability:
Relative variations in the small piece of the full resolution synthesis spectra:
Relative Change
0.04
0.03
0.02
0.01
0
510
511
512
513
514
515
516
Wavelength (nm)
517
518
519
520
very active
active
quiet (reference at 0 level)
The low resolution irradiance variations correspond to a smoothed
form of these high-resolution variations and should be interpreted
in terms of the detailed spectrum that forms over a wide range of
heights in the solar atmosphere and results from various physical
processes.
In very active cases the sunspot deficit may overwhelm the plage
excess, and in less active cases the reverse is true. This balance is
strongly wavelength dependent and also affects the TSI.
Section 2
Comparison of model and SIM observations
through a solar rotation period with strong irradiance
modulation
We find several interesting features in comparing the model
results with the spectral irradiance observed with the SIM
instrument and the Total Solar Irradiance (TSI) observed by
the TIM instrument, both instruments aboard the SORCE
spacecraft.
For the determining the area of the various features, we
used images obtained by the Precision Solar Photometric
Telescope (PSPT) data at the High Altitude Observatory.
Areas of the active region features
0.0025
Fractional Areas
0.002
0.0015
0.001
5 .10
4
0
0
5
10
Days since May 31, 2003
Medium Plage (multiplied by 1/6)
Bright Plage (multiplied by 1/3)
Sunspot Umbra
15
20
Model calculated irradiance and the TSI from TIM
Irradiance (relative to model C)
1.0005
1
0.9995
0.999
0.9985
0
5
10
15
Days since May 31, 2003
TSI from TIM
Synthesis V1 at 1553 nm
Synthesis V1 at 886 nm
Synthesis V1 at 791 nm
1 for reference
20
SIM observed irradiance and the TSI from TIM
The data is normalized to the day 21 (June 20, 2003)
Irradiance (relative to arbitrary value)
1.0005
1
0.9995
0.999
0
5
10
15
Days since May 31, 2003
20
TSI from TIM
SIM at 1564 nm
SIM at 881 nm
SIM at 788 nm
1 for reference
The most striking is the observed IR brightening due to
trailing plage, while the models would indicate it should be
absent or reversed. Thus, overall plage appears not dark but
bright in the band 1.2 - 3 microns.
XPS Ly alpha data showing the June rotation
Note the offset of the peaks compared with TSI and TIM
8.5
Irradiance (mW/m^2)
8
7.5
7
6.5
0
5
10
Days since May 31, 2003
15
20
XPS
Synthesis
XPS Ly alpha data showing the strong modulation periods around June
8.5
Irradiance (mW/m^2)
8
7.5
7
6.5
40
XPS
Synthesis
20
0
Days since May 31, 2003
20
40
60
TSI from TIM showing a few strong modulation periods
Total Solar Irradiance (W/m^2)
1362.5
1362
1361.5
1361
1360.5
1360
1359.5
40
20
0
20
Day since May 31, 2003
40
60
Spectral Solar Irradiance (W/m^2/nm)
1501 nm band from SIM showing the same strong modulation periods
0.2646
0.2644
40
20
0
20
Days since May 31, 2003
40
60
Spectral Solar Irradiance (W/m^2/nm)
652 nm band from SIM showing the same strong modulation periods
1.506
1.505
1.504
1.503
40
20
0
20
Days since May 31, 2003
40
60
Spectral Solar Irradiance (W/m^2/nm)
767 nm band from SIM showing the same strong modulation periods
1.17
1.169
1.168
1.167
40
20
0
20
Days since May 31, 2003
40
60
Conclusions:
• The IR range 1.2–3 microns varies more than it was thought
to vary and displays plage in a similar way as the visible but
with less amplitude and differences in shape.
• The TSI plot is very close to the 1.5 micron band and has
more differences with the visible bands. The differences are
mainly in the irradiance bumps seen leading the sunspot dips,
and in the delayed and wider bumps trailing these dips.
• The range 600 - 900 nm data shows very good agreement
between models and observations and displays a sawtoothlike appearance with gradual irradiance decreases leading the
sunspot dip and short-lived but very strong trailing increases.
• In the visible irradiance the trailing short-lived increases
occur as plage moves towards the limb while the large
sunspots disappear from the disk. The leading decreases
result from these large sunspots moving from the limb to
disk-center with little leading plage in the visible.
• The behavior of the IR irradiance still needs to be interpreted
in the light of the SIM data because it does not match our
previous model expectations.
• The long-term trends of the TSI may be more dominated by
the IR and UV than for the visible (i.e., the layers below and
above the visible photosphere). This is because in the visible
the sunspot deficit may nearly completely cancel or
overwhelm the plage increase while this cancellation may not
occur in the UV and IR.
June 6, 2003, white light image
Before the irradiance dip
June 9, 2003, white light image
The irradiance dip
June 17, 2003, white light image
The maximum irradiance after the dip.
June 23, 2003, white light image
The irradiance back to the level before the dip.
Section 3
Solar Atmosphere Radiative Output Modeling
Version 2 - 2001 - …
Overarching Goals:
• Understand new observations and develop and improve an extended
standard set of atmospheric models.
• Help understand the effects of magnetic fields on the spectral radiance
and quantify magnetic heating.
• Obtain insight on the fast- and slow-MHD wave modes propagation in
the chromosphere and their effects on the observations and the radiative
losses.
• Provide a platform for MHD modeling of physical processes for
heating/cooling in magnetic regions from the photosphere to the top of
the chromosphere-corona transition region.
Current Objectives:
• Compute accurately the spectral radiance, visible, IR, and UV spectral
regions for any 1-dimensional dynamic and MHD as well as static solartype atmospheric model.
• Compute in detail the radiative losses at all atmospheric layers and all
wavelengths for any models.
• Couple the full non-LTE (with PRD when necessary) radiative transfer
calculations with magneto-hydrodynamic calculations.
• Achieve a good set of modules and services for future study of physical
mechanisms of MHD chromospheric heating, e.g., by including the
Pedersen effect.
Methods:
¾ Portable C++ Object Oriented code library to run in Windows-Unix,
with networking, client-server, and relational databases. Easy to use
and extend in many follow-up projects.
Emitted Spectra
I(mu,lambda)
File
Radiative Losses
q(height)
File
Atomic
Species
Continua
Mean Intensity
and Net Radiative
Brackett Files
Molecular
Species
Continua
Radiative Transfer
Calculations
Molecular
Species Lines
Atomic
Species Lines
Atomic Species
Ionization &
Level
Populations File
Populations &
Ionization Statistical
Equilibrium
Atmospheric
Model File
¾ Calculate an extended set of models including more detailed ones,
dynamic and time-dependent snapshot models that match detailed
observations.
¾ Include the full effects of time-dependent flows and diffusion (selfand thermal diffusion) in elemental ionization and exploring
abundance variations.
¾ Include the main molecular species, CH, OH, MgH, NH, CN, CO, and
others in LTE or non-LTE if enough rate coefficients data is available.
¾ For neutral and singly ionized species compute ionizations and level
populations in full NLTE, and compute lines in PRD when relevant.
¾ For ions higher than singly ionized compute statistical equilibrium in
the optically thin regime but also with all non-local effects of
irradiation and flows and diffusion particle transport.