Differential photometry of magnetic faculae

Journal Article · Sun Sep 15 04:00:00 EDT 1985 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/163490· OSTI ID:6328797

Foukal, P; Duvall, T Jr

Previous photometric observations that we 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. We present here 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 (and thus in photospheric penetration depth) between the continuum passbands. We show that our difference signals is directly sensitive to changes in the temperature gradient near tau/sub 0.5/ = 1 between quite photosphere and faculae. The measured change in difference signal between faculae and photosphere implies in the facular atmosphere than in the photosphere implies a 20% lower temperature gradient immediately. A decreaase in temperature gradient at tau/sub 0.5/roughly-equal1 seems to be a feature of thermal models of slender flux tubes, caused by heating of the facular atmosphere by intense radiation from the walls of the facular Wilson depression. We discuss how further extension of this differential photometric technique could be helpful in deciding between a thermal and nonthermal explanation of facular brightness at photospheric levels.

• Research Organization: Atmospheric and Environmental Research, Inc.
• OSTI ID: 6328797
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 296:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANIONS
ATMOSPHERES
ATOMIC MODELS
CHARGED PARTICLES
FACULAE
FRAUNHOFER LINES
HYDROGEN IONS
HYDROGEN IONS 1 MINUS
IONS
MAGNETIC FIELDS
MATHEMATICAL MODELS
OPACITY
OPTICAL PROPERTIES
PHOTOMETRY
PHOTOSPHERE
PHYSICAL PROPERTIES
SOLAR ACTIVITY
SOLAR ATMOSPHERE
VISIBILITY