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Title:
Differential photometry of magnetic faculae
Authors:
Foukal, P.; Duvall, T., Jr.
Affiliation:
AA(Atmospheric and Environmental Research, Inc., Cambridge, MA), AB(NASA, Goddard Space Flight Center, Tucson, AZ)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 296, Sept. 15, 1985, p. 739-745. (ApJ Homepage)
Publication Date:
09/1985
Category:
Solar Physics
Origin:
STI
NASA/STI Keywords:
Faculae, Near Infrared Radiation, Photosphere, Solar Magnetic Field, Stellar Spectrophotometry, Atmospheric Optics, Atmospheric Temperature, Fraunhofer Lines, Optical Thickness, Solar Atmosphere, Stellar Models
DOI:
10.1086/163490
Bibliographic Code:
1985ApJ...296..739F

Abstract

Previous photometric observations carried out at the KPNO vacuum telescope showed that faculae become clearly visible near disk center in the difference of two widely separated (green and red) continuum passbands. The authors present new observations extending this technique to the near-infrared, to demonstrate that the main factor determining the facular visibility is the difference in H- opacity between the continuum passbands. It is shown that the difference signal is directly sensitive to changes in the temperature gradient near tau0.5 = 1 between quiet photosphere and faculae. The measured facular temperature gradient is compared with that given by empirical facular models based on Fraunhofer line observations, and with theoretical predictions.

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Database: Astronomy
Physics
arXiv e-prints