Imperial College London
Dr Yvonne Unruh

DrYvonneUnruh

Faculty of Natural Sciences, Department of Physics

Reader in Astrophysics
 
 
 
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Contact

 

y.unruh Website

 
 
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Location

 

1114Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Tagirov:2019:0004-6361/201935121,
author = {Tagirov, RV and Shapiro, AI and Krivova, NA and Unruh, YC and Yeo, KL and Solanki, SK},
doi = {0004-6361/201935121},
journal = {Astronomy & Astrophysics},
pages = {1--8},
title = {Readdressing the UV solar variability with SATIRE-S: non-LTE effects},
url = {http://dx.doi.org/10.1051/0004-6361/201935121},
volume = {631},
year = {2019}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Context. Solar spectral irradiance (SSI) variability is one of the key inputs to models of the Earth’s climate. Understanding solar irradiance fluctuations also helps to place the Sun among other stars in terms of their brightness variability patterns and to set detectabilitylimits for terrestrial exoplanets.Aims. One of the most successful and widely used models of solar irradiance variability is Spectral And Total Irradiance REconstruction model (SATIRE-S). It uses spectra of the magnetic features and surrounding quiet Sun that are computed with the ATLAS9spectral synthesis code under the assumption of local thermodynamic equilibrium (LTE). SATIRE-S has been at the forefront of solarvariability modelling, but due to the limitations of the LTE approximation its output SSI has to be empirically corrected below 300 nm,which reduces the physical consistency of its results. This shortcoming is addressed in the present paper.Methods. We replaced the ATLAS9 spectra of all atmospheric components in SATIRE-S with spectra that were calculated using theNon-LTE Spectral SYnthesis (NESSY) code. To compute the spectrum of the quiet Sun and faculae, we used the temperature anddensity stratification models of the FAL set.Results. We computed non-LTE contrasts of spots and faculae and combined them with the corresponding fractional disc coverages,or filling factors, to calculate the total and spectral irradiance variability during solar cycle 24. The filling factors have been derivedfrom solar full-disc magnetograms and continuum images recorded by the Helioseismic and Magnetic Imager on Solar DynamicsObservatory (SDO/HMI).Conclusions. The non-LTE contrasts yield total and spectral solar irradiance variations that are in good agreement with empiricallycorrected LTE irradiance calculations. This shows that the empirical correction applied to the SATIRE-S total and spectral solarirradiance is consistent with results from non-LTE computations.
AU  - Tagirov,RV
AU  - Shapiro,AI
AU  - Krivova,NA
AU  - Unruh,YC
AU  - Yeo,KL
AU  - Solanki,SK
DO  - 0004-6361/201935121
EP  - 8
PY  - 2019///
SN  - 0004-6361
SP  - 1
TI  - Readdressing the UV solar variability with SATIRE-S: non-LTE effects
T2  - Astronomy & Astrophysics
UR  - http://dx.doi.org/10.1051/0004-6361/201935121
UR  - https://www.aanda.org/articles/aa/abs/2019/11/aa35121-19/aa35121-19.html
UR  - http://hdl.handle.net/10044/1/74414
VL  - 631
ER  -
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