J/ApJ/707/482 Models of the solar atmosphere. III. (Fontenla+, 2009)
Semiempirical models of the solar atmosphere.
III. Set of non-LTE models for Far-Ultraviolet/Extreme-Ultraviolet irradiance
computation.
Fontenla J.M., Curdt W., Haberreiter M., Harder J., Tian H.
<Astrophys. J., 707, 482-502 (2009)>
=2009ApJ...707..482F 2009ApJ...707..482F
ADC_Keywords: Sun ; Models, atmosphere ; Ultraviolet
Keywords: solar-terrestrial relations - Sun: activity - Sun: atmosphere -
Sun: chromosphere - Sun: faculae, plages - Sun: UV radiation
Abstract:
Semiempirical atmospheric models of solar surface features as observed
at moderate resolution are useful tools for understanding the observed
solar spectral irradiance variations. Paper I described a set of
models constructed to reproduce the observed radiance spectrum for
solar surface features at ∼2 arcsec resolution that constitute an
average over small-scale features such as granulation. Paper II showed
that a revision of previous models of low-chromospheric inter-network
regions explains the observed infrared CO lines in addition to the UV
and radio continuum from submillimeter to centimetric wavelengths. The
present paper (1) shows that the CaII H and K line wing observations
are also explained by the new quiet-Sun-composite model, (2)
introduces new low-chromospheric models of magnetic features that
follow the ideas in Paper II (Fontenla et al. 2007ApJ...667.1243F 2007ApJ...667.1243F),
(3) introduces new upper chromospheric structures for all quiet-Sun
and active-region models, and (4) shows how the new set of models
explains EUV/FUV observations of spectral radiance and irradiance.
This paper also discusses the chromospheric radiative-loss estimates
in each of the magnetic features. The new set of models provides a
basis for the spectral irradiance synthesis at EUV/FUV wavelengths
based on the features observed on the solar surface.
Description:
Observations by the SOHO/SUMER instrument have been used to produce
the atlas of Curdt et al. (2001, Cat. J/A+A/375/591) showing the
spectrum of the average quiet-Sun in the wavelength range
700-1500Å. We use these observations for defining a set of
atmospheric models based on the distribution of observed intensities
at a few wavelengths.
The quiet-Sun components are defined from the CaII K line intensity
enhancements as described by Fontenla & Harder (2005MmSAI..76..826F 2005MmSAI..76..826F).
Observations of the solar disk in the CaII K line from several
facilities are available. We currently use images obtained by the
Precision Solar Photometric Telescope instrument at the Mauna Loa
Solar Observatory (hereafter MLSO/PSPT). These data (see
http://lasp.colorado.edu/pspt_access/) provide an almost continuous
and accurate record since 2005 January and permit comparison of the
computed with observed spectral irradiance.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
model1.dat 195 91 *Atmospheric model 1001; feature B
model2.dat 195 91 *Atmospheric model 1002; feature D - network
model3.dat 195 91 *Atmospheric model 1003; feature F - enhanced
network
model4.dat 195 91 *Atmospheric model 1004; feature H
model5.dat 195 101 *Atmospheric model 1005; feature P
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Notes on *.dat: The units of all data are in the CGS system. Designation of
features:
----------------------------------------------------------------
Letter Model Feature description Pressure Disk
Index (a) (b)
----------------------------------------------------------------
B 1001 Quiet-Sun inter-network 0.235 <1.02
D 1002 Quiet-Sun network lane 0.340 1.02-1.08
F 1003 Enhanced network 0.552 1.08-1.19
H 1004 Plage (that is not facula) 1.00 1.19-1.43
P 1005 Facula (i.e., very bright plage) 1.62 1.43-1.80
S 1006 Sunspot umbra 3.86
R 1007 Sunspot penumbra 2.10
----------------------------------------------------------------
Note (a): Pressure at 2x105K(dyne/cm2)
Note (b): Disk center contrast in CaII K MLSO/PSPT
----------------------------------------------------------------
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See also:
J/A+A/531/A173 : Spectroscopy of CaII-H line at solar limb (Beck+, 2011)
J/A+A/493/1099 : CaII HK emission in rapidly rotating stars (Schroeder+, 2009)
J/A+A/423/1109 : Center-to-limb variation of quiet Sun (Allende+, 2004)
J/A+A/375/591 : SUMER Spectral Atlas of Solar Disk Features (Curdt+, 2001)
J/A+AS/126/281 : Solar disk spectrum (660-1175A) (Curdt+ 1997)
http://www.digidyna.com/ : Solar Radiation Physical Modeling page
http://lasp.colorado.edu/pspt_access/ : Precision Solar Photometric Telescope
Byte-by-byte Description of file: model[12345].dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Ind [0,100] Index for the height (1)
5- 24 E20.13 cm h [-1.1e+07,2.03933e+08] Altitude on the Sun
above an arbitrary reference point (2)
27- 45 E19.13 K T [3790,201234] Temperature (3)
48- 60 E13.7 cm-3 ne [4.47707e+09,3.81523e+15] Electron density
63- 75 E13.7 cm-3 np [1.53999e+09,3.78703e+15] Proton density
78- 90 E13.7 cm-3 na [3769.84,1.40664e+17] Neutral hydrogen density
93-105 E13.7 cm-3 nh [3.7253e+09,1.43198e+17] Total hydrogen
density (4)
108-120 E13.7 cm/s vt [52017,2.5e+06] Turbulence velocity (5)
123-135 E13.7 cm/s2 accel [644.870,7000] Non-gravitational acceleration (6)
138-150 E13.7 --- bH- [0.439154,917.888] Departure from LTE
coefficient for H- (7)
153-165 E13.7 --- --- [0,0] (vel)
168-180 E13.7 --- bH2 [0.554186,917.888] Departure from LTE
coefficient for H2 molecule (8)
183-195 E13.7 --- --- [1,1] This value is always 1, and not relevant
here
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Note (1): Note that these start at 0 and increasing index correspond to
decreasing altitude.
Note (2): This reference point is close but not exactly at tau_5000=1.
Note (3): The models assume the electron and ion kinetic temperatures are
described by this value.
Note (4): This value is always the sum of the previous two, but the listing
numerical precision may make it slightly different.
Note (5): This value is used a microturbulent broadening velocity.
Note (6): This value is used for the pressure balance as described in the paper.
Note (7): The LTE is considered with respect to electron attachment,
i.e. e+H←>H-+hν, but the calculation also considers other
reaction channels.
Note (8): The LTE is considered with respect to H2 dissociation,
i.e. H+H←>H2+hν, but the calculation also considers
other reaction channels.
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History:
From electronic version of the journal
Acknowledgements:
For questions please contact Juan M Fontenla at either
fontenla{at}colorado.edu or johnf{at}digidyna.com
References:
Fontenla et al. Paper I. 2006ApJ...639..441F 2006ApJ...639..441F
Fontenla et al. Paper II. 2007ApJ...667.1243F 2007ApJ...667.1243F
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 30-Dec-2011