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

Abstract

Modeling the variability of the solar spectral irradiance is a key factor for understanding the solar influence on the climate of the Earth. As a first step to calculating the solar spectral irradiance variations we reproduce the solar spectrum for the quiet Sun over a broad wavelength range with an emphasis on the UV. We introduce the radiative transfer code COSI which calculates solar synthetic spectra under conditions of non-local thermodynamic equilibrium (NLTE). A self-consistent simultaneous solution of the radiative transfer and the statistical equation for the level populations guarantees that the correct physics is considered for wavelength regions where the assumption of local thermodynamic equilibrium (LTE) breaks down. The new concept of iterated opacity distribution functions (NLTE-ODFs), through which all line opacities are included in the NLTE radiative transfer calculation, is presented. We show that it is essential to include the line opacities in the radiative transfer to reproduce the solar spectrum in the UV. Through the implemented scheme of NLTE-ODFs the COSI code is successful in reproducing the spectral energy distribution of the quiet Sun.

arXiv comment13 pages, 9 figures. accepted for publication in Astronomy and Astrophysics

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Cited by in corpus (22)

• Recent variability of the solar spectral irradiance and its impact on climate modelling
• A new approach to long-term reconstruction of the solar irradiance leads to large historical solar forcing
• NLTE solar irradiance modeling with the COSI code
• Solar cycle variation in solar irradiance
• Solar irradiance variability: A six-year comparison between SORCE observations and the SATIRE model
• The LYRA Instrument Onboard PROBA2: Description and In-Flight Performance
• Non-LTE Radiative Transfer with Turbospectrum
• Reconstruction of solar UV irradiance since 1974
• UV solar irradiance in observations and the NRLSSI and SATIRE-S models
• PICARD SODISM, a space telescope to study the Sun from the middle ultraviolet to the near infrared
• Photometric Properties of Network and Faculae Derived from HMI Data Compensated for Scattered-Light
• Interpretation of Solar Irradiance Monitor measurements through analysis of 3D MHD simulations
• Effects of continuum fudging on non-LTE synthesis of stellar spectra. I. Effects on estimates of UV continua and Solar Spectral Irradiance variability
• Solar EUV Spectrum Calculated for Quiet Sun Conditions
• Readdressing the UV solar variability with SATIRE-S: non-LTE effects
• NLTE modelling of integrated light spectra. Abundances of barium, magnesium, and manganese in a metal-poor globular cluster
• Eclipses observed by LYRA - a sensitive tool to test the models for the solar irradiance
• The Measurement of Solar Diameter and Limb Darkening Function with the Eclipse Observations
• Analysis and modeling of solar irradiance variations
• Solar Atmosphere Radiative Transfer Model Comparison based on 3D MHD simulations
• The Measurement of Solar Diameter and Limb Darkening Function with the Eclipse Observations. Thesis work
• Influence of the Conversion Layer on the Dispersion Relation of Waves in the Solar Atmosphere