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Dark Off-limb Gap: Manifestation of a Temperature Minimum and the Dynamic Nature of the Chromosphere
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SYSNO ASEP 0562599 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Dark Off-limb Gap: Manifestation of a Temperature Minimum and the Dynamic Nature of the Chromosphere Author(s) Kuridze, D. (GB)
Heinzel, Petr (ASU-R) RID, ORCID
Koza, J. (SK)
Oliver, R. (ES)Number of authors 4 Article number 56 Source Title Astrophysical Journal - ISSN 0004-637X
Roč. 937, č. 2 (2022)Number of pages 11 s. Publication form Online - E Language eng - English Country GB - United Kingdom Keywords spectroscopy ; ground telescopes ; solar chromosphere Subject RIV BN - Astronomy, Celestial Mechanics, Astrophysics OECD category Astronomy (including astrophysics,space science) Method of publishing Open access Institutional support ASU-R - RVO:67985815 UT WOS 000861000000001 EID SCOPUS 85139752752 DOI 10.3847/1538-4357/ac8d8e Annotation We study off-limb emission of the lower solar atmosphere using high-resolution imaging spectroscopy in the H beta and Ca ii 8542 angstrom lines obtained with the CHROMospheric Imaging Spectrometer (CHROMIS) and the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1 m Solar Telescope. The H beta line-wing images show the dark intensity gap between the photospheric limb and chromosphere, which is absent in the Ca ii images. We calculate synthetic spectra of the off-limb emissions with the RH code in one-dimensional spherical geometry and find good agreement with the observations. The analysis of synthetic line profiles shows that the gap in the H beta line-wing images maps the temperature minimum region between the photosphere and chromosphere due to the well-known opacity and emissivity gap of Balmer lines in this layer. However, the observed gap is detected farther from the line core in the outer line-wing positions than in the synthetic profiles. We found that an increased microturbulence in the model chromosphere is needed to reproduce the dark gap in the outer line wing, suggesting that the observed H beta gap is the manifestation of the temperature minimum and the dynamic nature of the solar chromosphere. The temperature minimum produces a small enhancement in synthetic Ca ii line-wing intensities. Observed off-limb Ca ii line-wing emissions show similar enhancement below the temperature minimum layer near the edge of the photospheric limb. Workplace Astronomical Institute Contact Radka Svašková, bibl@asu.cas.cz, Tel.: 323 620 326 Year of Publishing 2023 Electronic address https://hdl.handle.net/11104/0335141
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