modeling the solar euv irradiance margit haberreiter pmod/wrc, davos, switzerland ipc xi sept 26 –...
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Modeling the Solar EUV irradiance
Margit Haberreiter
PMOD/WRC, Davos, Switzerland
IPC XI
Sept 26 – Oct 15, 2010
Picard
Absorption of EUV in the Earth‘s atmosphere
Altitude-wavelength dependence of energy deposition from solar irradiance
units of Log10(Wm-4)
From Solomon and Qian 2005
Solar minimum conditions
EUV varies by a factor of 2 and more!!
Peculiar Minimum 23/24
Claus Froehlich, PMOD TSI composite
Is there an EUV long-term trend?
The SOHO/SEM measurements (36-34 nm)indicate a decrease in the EUV by15%
Uncertainty ~ 6%
Not explained by F10.7 or sunspot number
What is the role of coronal holes?
Solomon et al, 2010, GRL, 37, L16103 15%decrease
SDO/AIA image
EUV spectrum
• Wavelengths –UV: 120 – 400 nm
–EUV: 10 – 120 nm
• Contribution from the – Chromophere
– Transition region
– Corona
Solar Modeling (SolMod)
• Multi level atoms– 373 ions, from H to Ni with ioncharge 25– ~14’000 atomic levels– ~170’000 spectral lines – Statistical equation is solved to get the level populations
• Chromosphere and transition region – for ioncharge 2: – full NLTE (Fontenla et al., 2006; 2007; 2009)
– plus optically thin transition region lines– Spherical symmetry
• Corona– ioncharge >2 – optically thin, i.e. collisions and spontaneous emission– Line of sight integration accounts for opacity– Spherical symmetry
Masks from Precision Solar Photometric Telescope
Disk mask on 2005/9/12 obtained from PSPT data, Mauna Loa, Hawaiihttp://lasp.colorado.edu/pspt_access/
(R) Sunspot Penumbra(S) Sunspot Umbra(P) Faculae(H) Plage(F) Active network(D) Quiet network (white)
(B) Intergranular Cells
Determined by the contrast as a function of the position on the disk-Only possible with respect to a -normalized quiet Sun intensity
Continuum, 607 nm (PICARD)
Ca II 393.4, FWHM=0.27nm
Solar Chromosphere (Ca II) of quiet Sun
IntergranularCellsModel B
Quiet NetworkModel D
Fontenla et al., 2009, ApJ
ss
ActiveNetworkModel F
0.1 1 10 100 1 103
1 104
1 105
4000
6000
8000
B 1001D 1002F 1003H 1004P 1005
B 1001D 1002F 1003H 1004P 1005
Pressure (dyn cm^-2)
Tem
pera
ture
(K
)
FaculaePlageActive networkQuiet networkIntergranular Cells
Fontenla et al., 2009, ApJ 707, 482-502
G-Band of CH molecular lines
Fontenla et al., 2009, ApJ 707, 482-502
Violet CN Band
Fontenla et al., 2009, ApJ 707, 482-502
Modeling the EUVe.g. Fe XV 284 Å
Coronal models
• Coronal Models are based on temperature and densities given by
• Doschek (1997), ApJ, 476, 903
• Singh et al., 1982, J. Astrophys. 3, 249
• Cranmer et al, 2007, ApJS 171, 520
Spherical Symmetry
Allows the calculation of intensities at and beyond the limb
(e.g. Haberreiter et al. 2008)
Account for corona over 2 x area of solar disk
Adopted from Mihalas, 1978
Spherical symmetry
28.4 28.41 28.42
5 103
0.01
sphericalplane-parallel
Wavelength (nm)
Irra
dian
ce (
W m
-2 n
m-1
)
Optical depth• Fe XV 17.1 nm:
– Disk center: max = 0.06
– Limb: (r=1.02): max = 0.63 (~900,000K)
• Fe XV 19.5 nm:
– Disk center: max = 0.06
– Limb: (r=1.02): max = 0.34 (~1,100,000K)
• Fe XV 28.4 nm:
– Disk center: max = 0.39
– Limb: (r=1.02): max = 0.88 (~2,000,000K)
Spectrum from Corona, TR and Chromosphere
50 1001 10
7
1 106
1 105
1 104
1 103
0.01
0.1
1
SPRM 1SPRM 2SPRM 3SPRM 4SPRM 5
Wavelength (nm)
Irra
dian
ce (
erg
cm-2
s-1
nm
-1)
EUV spectrum
Haberreiter, 2010, submitted to Solar PhysicsEVE rocket calibration flight: Chamberlin et al., 2009, GRL
EUV spectrum
Haberreiter, 2010, submitted to Solar PhysicsEVE rocket calibration flight: Chamberlin et al., 2009, GRL
SOHO/EIT images
284 Angstroms171 Angstroms
195 Angstroms 304 Angstroms
Fe XII 1.3x105 K He II 8x104 K
He II 30.4 nm
Fe XV 28.4 nm
Fe IX 17.1 nm
Fe XII 19.5 nm
EIT passbands
Fe IX 17.1 nm
Fe XII 19.5 nm
Fe XV 28.4 nm
He II 30.4 nm
EIT wavelengthsSRPMEVE
Variability of solar activity features
EIT 17.1nm07/01/2005
EIT 19.5 nm10/01/2002
EIT 28.4 nm10/10/2003
EIT 30.4 nm07/10/2006
coronal holes – quiet Sun – quiet coronal network – active coronal network - hot loop – super hot loop
EIT image analysis
• Radial dependence for outer corona
• Thresholds based on intenstiy histogram of the EIT images
• Maximum value of histogram varies with solar cycle (in particular for 284 Ǻ)
• Does the coronal hole/quiet Sun intensity changes with solar cycle→ identification of coroanl features not trivial
Does the quiet Sun intensity change
Barra et al, 2009 already performed the analysis for 3 components.
Outlook: Shape of coronal holes influences strength of solar wind streams
Gibson et al, 2009
Conclusions• Good agreement between the synthetic spectra
and the observed EVE quiet Sun spectrum
• Our calculations indicate that opacity effects have to be taken into account for some prominent lines, i.e. the EIT lines
• Challenge for feature identification: potential change of coronal hole and quiet Sun intensity
• Spectral reconstruction over a full solar cycle still to come....
Further plans• Valicate the identification scheme of coronal
holes, active regions
• Account for temporal variability
– changing distribution of features, e.g. coronal holes, active regions
• LYRA measurements very important for validation/comparison
• 1 TB/day from SDO/AIA and SDO/EVE ....
References
• Cranmer et al, 2007, Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence, ApJS 171, 520
• Doschek (1997), Emission Mesaures and Electron Densities for the solar transition region, ApJ, 476, 903.
• Fontenla et al., 2009, Semi-empirical Models of the Solar AtmosphereIII. Set of NLTE Models for FUV/EUV Irradiance Computation, ApJ, accepted for publication
• Klimchuk (2006), On Solving the Coronal Heating Problem, Solar Physics 234, 41-77
• Singh et al., 1982, Eclipse Observations of Coronal Emission Lines, J. Astrophys. 3, 249