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  Nonequilibrium Equation of State in Stellar Atmospheres

Anusha, L. S., van Noort, M., & Cameron, R. H. (2021). Nonequilibrium Equation of State in Stellar Atmospheres. The Astrophysical Journal, 911(1): 71. doi:10.3847/1538-4357/abe45d.

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 Creators:
Anusha, L. S.1, Author              
van Noort, Michiel2, Author              
Cameron, Robert H.3, Author              
Affiliations:
1Max Planck Institute for Solar System Research, Max Planck Society, ou_1125546              
2Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              
3Department Solar and Stellar Interiors, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832287              

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Free keywords: Radiative magnetohydrodynamics; Radiative transfer; Radiative transfer simulations; Stellar atmospheres; Computational methods; Solar atmosphere; Stellar chromospheres; Ionization; Solar chromosphere; Recombination; Spectroscopy; Theoretical techniques
 Abstract: In the stellar chromospheres, radiative energy transport is dominated by only the strongest spectral lines. For these lines, the approximation of local thermodynamic equilibrium (LTE) is known to be very inaccurate, and a state of equilibrium cannot be assumed in general. To calculate the radiative energy transport under these conditions, the population evolution equation must be evaluated explicitly, including all time-dependent terms. We develop a numerical method to solve the evolution equation for the atomic-level populations in a time-implicit way, keeping all time-dependent terms to first order. We show that the linear approximation of the time dependence of the populations can handle very large time steps without losing accuracy. We reproduce the benchmark solutions from earlier, well-established works in terms of non-LTE kinetic equilibrium solutions and typical ionization/recombination timescales in the solar chromosphere.

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Language(s): eng - English
 Dates: 2021
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.3847/1538-4357/abe45d
 Degree: -

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Title: The Astrophysical Journal
Source Genre: Journal
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Publ. Info: Bristol; Vienna : IOP Publishing; IAEA
Pages: - Volume / Issue: 911 (1) Sequence Number: 71 Start / End Page: - Identifier: ISSN: 0004-637X
CoNE: https://pure.mpg.de/cone/journals/resource/954922828215_3