Photometric observations of facular contrasts near the solar limb

Abstract

view Abstract Citations (26) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photometric Observations of Facular Contrasts near the Solar Limb Lawrence, J. K. ; Chapman, G. A. Abstract Digital, photometric images of several active regions near the solar limb made with 1.5 A effective bandpass at 6264 A are analyzed. From three to ten images were made per day on several days during 1983, 1984, and 1987 with the San Fernando Observatory 28 cm vacuum solar telescope and spectroheliograph and 512 element Reticon linear diode arrays. Pixel spacing is 0.94 arcsec. Pixels in each image were sorted into quiet sun and facular intensity distributions by mu value, where mu = cos theta and theta is the heliocentric angle between the pixel and the direction of earth. These distributions were converted to overall average values of facular pixel contrast relative to the quiet sun background by mu value, and a center-limb variation of contrast per facular element was derived. If one is careful to distinguish between contrasts per unit projected area (pixel contrasts) and contrasts per facular element or individual flux tube, the results are in reasonable agreement with those of other workers. The center-limb contrast variation resembles a 'hot wall' model of facular emission, with indications of an additional emitting component which protrudes above the photospheric level. Publication: The Astrophysical Journal Pub Date: December 1988 DOI: 10.1086/166986 Bibcode: 1988ApJ...335..996L Keywords: Astronomical Photometry; Faculae; Solar Activity; Solar Limb; Digital Data; Spatial Resolution; Spectroheliographs; Visible Spectrum; Solar Physics; SUN: ACTIVITY; SUN: FACULAE full text sources ADS |