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A new sunspot umbral model and its variation with the solar cycle
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1986
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Semiempirical model atmospheres for the darkest parts of large sunspot umbrae—known as umbral cores—are presented to study their physical properties. Using general‑purpose computational procedures, the authors construct three umbral core models representing the early, middle, and late solar‑cycle phases, while accounting for atomic, opacity, and abundance uncertainties and providing a reference quiet‑photosphere model. The time‑varying umbral core model reproduces recent spectral‑energy‑distribution intensity measurements and the observed center‑limb variation, with the three models corresponding to dark, average, and bright umbral cores. Published in The Astrophysical Journal (July 1986), DOI 10.1086/164342.
view Abstract Citations (550) References (77) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A New Sunspot Umbral Model and Its Variation with the Solar Cycle Maltby, P. ; Avrett, E. H. ; Carlsson, M. ; Kjeldseth-Moe, O. ; Kurucz, R. L. ; Loeser, R. Abstract Semiempirical model atmospheres are presented for the darkest parts of large sunspot umbrae, regions have called umbral cores. The approach is based on general-purpose computational procedures that are applicable to different types of stellar atmospheres. It is shown that recent umbral intensity measurements of the spectral energy distribution may be accounted for by an umbral core atmospheric model that varies with time during the solar cycle; the observed center-limb variation can be accounted for by the properties of the model. Three umbral core models are presented, corresponding to the early, middle, and late phases of the solar cycle. These three models also may be regarded as having the properties of dark, average, and bright umbral cores respectively. The effects of atomic, opacity, and abundance data uncertainties on the model calculations are briefly discussed. For comparison, a new reference model for the average quiet solar photosphere is given. Publication: The Astrophysical Journal Pub Date: July 1986 DOI: 10.1086/164342 Bibcode: 1986ApJ...306..284M Keywords: Atmospheric Models; Periodic Variations; Solar Atmosphere; Solar Cycles; Sunspots; Umbras; Solar Activity; Solar Limb; Spectral Energy Distribution; Stellar Models; Solar Physics; SUN: ACTIVITY; SUN: ATMOSPHERE; SUN: SUNSPOTS full text sources ADS |