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Title:
A new sunspot umbral model and its variation with the solar cycle
Authors:
Maltby, P.; Avrett, E. H.; Carlsson, M.; Kjeldseth-Moe, O.; Kurucz, R. L.; Loeser, R.
Affiliation:
AA(Oslo, Universitet, Norway), AB(Oslo, Universitet, Norway), AC(Oslo, Universitet, Norway), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 306, July 1, 1986, p. 284-303. Research supported by the Norges Almenvitenskapelige Forskningsrad and Norwegian Marshall Fund. (ApJ Homepage)
Publication Date:
07/1986
Category:
Solar Physics
Origin:
STI
NASA/STI Keywords:
ATMOSPHERIC MODELS, PERIODIC VARIATIONS, SOLAR ATMOSPHERE, SOLAR CYCLES, SUNSPOTS, UMBRAS, SOLAR ACTIVITY, SOLAR LIMB, SPECTRAL ENERGY DISTRIBUTION, STELLAR MODELS
DOI:
10.1086/164342
Bibliographic Code:
1986ApJ...306..284M

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.

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