NLTE model calculations for the solar atmosphere with an iterative treatment of opacity distribution functions

Haberreiter, M.; Schmutz, W.; Hubený, I.

doi:10.1051/0004-6361:200809503

Cited by 54 publications

(58 citation statements)

References 52 publications

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“…The salient features of the continuum spectra are the Balmer, Mg i, and Al i ionisation edges at 364.5 nm, 251.2 nm, and 207.8 nm, respectively. The feature around 290 nm is attributed by Haberreiter et al (2003) to a resonance in the Mg i 3 photoionisation cross section. While the Mg i and Al i edges can still be recognised in the "real" (i.e.…”

Section: Fraunhofer Linesmentioning

confidence: 88%

The role of the Fraunhofer lines in solar brightness variability

Шапиро

Solanki

Krivova

et al. 2015

A&A

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Context. The solar brightness varies on timescales from minutes to decades. A clear identification of the physical processes behind such variations is needed for developing and improving physics-based models of solar brightness variability and reconstructing solar brightness in the past. This is, in turn, important for better understanding the solar-terrestrial and solar-stellar connections. Aims. We estimate the relative contributions of the continuum, molecular, and atomic lines to the solar brightness variations on different timescales. Methods. Our approach is based on the assumption that variability of the solar brightness on timescales greater than a day is driven by the evolution of the solar surface magnetic field. We calculated the solar brightness variations employing the solar disc area coverage of magnetic features deduced from the MDI/SOHO observations. The brightness contrasts of magnetic features relative to the quiet Sun were calculated with a non-LTE radiative transfer code as functions of disc position and wavelength. By consecutive elimination of molecular and atomic lines from the radiative transfer calculations, we assessed the role of these lines in producing solar brightness variability. Results. We show that the variations in Fraunhofer lines define the amplitude of the solar brightness variability on timescales greater than a day and even the phase of the total solar irradiance variability over the 11-year cycle. We also demonstrate that molecular lines make substantial contribution to solar brightness variability on the 11-year activity cycle and centennial timescales. In particular, our model indicates that roughly a quarter of the total solar irradiance variability over the 11-year cycle originates in molecular lines. The maximum of the absolute spectral brightness variability on timescales greater than a day is associated with the CN violet system between 380 and 390 nm.

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Section: Fraunhofer Linesmentioning

confidence: 88%

The role of the Fraunhofer lines in solar brightness variability

Шапиро

Solanki

Krivova

et al. 2015

A&A

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“…6), which allows incorporation of the opacity from the background lines into the solution of statistical equilibrium equations (Haberreiter et al 2008). This background opacity diminishes the amount of the penetrating UV radiation and decreases the degree of metal ionization.…”

Section: Nlte Calculationsmentioning

confidence: 99%

“…Although the concept of the ODF allows the agreement between calculations and observations to be imporved, the ODF based on the Kurucz linelist (Haberreiter et al 2008) cannot solve the discrepancy with measurements. The most probable source of the problem is the inaccuracy of the atomic and molecular line list and possible missing continuum opacity.…”

Section: Nlte Calculationsmentioning

confidence: 99%

“…However, the significant disagreement between the calculated and measured solar UV flux as discussed above indicates that the computations still miss an essential part of the opacity. To compensate for this missing opacity, Haberreiter et al (2008) This approach proves itself successful, but it cannot be used to fit high-resolution spectra. Therefore, here we have extended the approach by Busá et al (2001) and Short & Hauschildt (2009) and included additional opacity in our NLTE-ODF scheme, as described below.…”

Section: Additional Opacities In Cosimentioning

confidence: 99%

“…Combining the radiative transfer code by Hamann & Schmutz (1987); Schmutz et al (1989) and spectral synthesis code SYNSPEC by Hubeny (1981), Haberreiter et al (2008) has developed the 1D spherical symmetrical COde for Solar Irradiance (COSI). The NLTE opacity distribution function (ODF) concept, which was implemented in this code, allows an indirect account for the NLTE effects in several million lines.…”

Section: Introductionmentioning

confidence: 99%

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NLTE solar irradiance modeling with the COSI code

Шапиро¹,

Schmutz²,

Schoell

et al. 2010

A&A

Self Cite

120

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Context. The solar irradiance is known to change on time scales of minutes to decades, and it is suspected that its substantial fluctuations are partially responsible for climate variations. Aims. We are developing a solar atmosphere code that allows the physical modeling of the entire solar spectrum composed of quiet Sun and active regions. This code is a tool for modeling the variability of the solar irradiance and understanding its influence on Earth. Methods. We exploit further development of the radiative transfer code COSI that now incorporates the calculation of molecular lines. We validated COSI under the conditions of local thermodynamic equilibrium (LTE) against the synthetic spectra calculated with the ATLAS code. The synthetic solar spectra were also calculated in non-local thermodynamic equilibrium (NLTE) and compared to the available measured spectra. In doing so we have defined the main problems of the modeling, e.g., the lack of opacity in the UV part of the spectrum and the inconsistency in the calculations of the visible continuum level, and we describe a solution to these problems. Results. The improved version of COSI allows us to reach good agreement between the calculated and observed solar spectra as measured by SOLSTICE and SIM onboard the SORCE satellite and ATLAS 3 mission operated from the Space Shuttle. We find that NLTE effects are very important for the modeling of the solar spectrum even in the visual part of the spectrum and for its variability over the entire solar spectrum. In addition to the strong effect on the UV part of the spectrum, NLTE effects influence the concentration of the negative ion of hydrogen, which results in a significant change of the visible continuum level and the irradiance variability.

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UV solar irradiance in observations and the NRLSSI and SATIRE‐S models

et al. 2015

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Total solar irradiance and UV spectral solar irradiance has been monitored since 1978 through a succession of space missions. This is accompanied by the development of models aimed at replicating solar irradiance by relating the variability to solar magnetic activity. The Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) and Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE‐S) models provide the most comprehensive reconstructions of total and spectral solar irradiance over the period of satellite observation currently available. There is persistent controversy between the various measurements and models in terms of the wavelength dependence of the variation over the solar cycle, with repercussions on our understanding of the influence of UV solar irradiance variability on the stratosphere. We review the measurement and modeling of UV solar irradiance variability over the period of satellite observation. The SATIRE‐S reconstruction is consistent with spectral solar irradiance observations where they are reliable. It is also supported by an independent, empirical reconstruction of UV spectral solar irradiance based on Upper Atmosphere Research Satellite/Solar Ultraviolet Spectral Irradiance Monitor measurements from an earlier study. The weaker solar cycle variability produced by NRLSSI between 300 and 400 nm is not evident in any available record. We show that although the method employed to construct NRLSSI is principally sound, reconstructed solar cycle variability is detrimentally affected by the uncertainty in the SSI observations it draws upon in the derivation. Based on our findings, we recommend, when choosing between the two models, the use of SATIRE‐S for climate studies.

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NLTE model calculations for the solar atmosphere with an iterative treatment of opacity distribution functions

Cited by 54 publications

References 52 publications

The role of the Fraunhofer lines in solar brightness variability

The role of the Fraunhofer lines in solar brightness variability

NLTE solar irradiance modeling with the COSI code

UV solar irradiance in observations and the NRLSSI and SATIRE‐S models

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