Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989apj...336l..33f&link_type=abstract
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 336, Jan. 1, 1989, p. L33-L35.
Astronomy and Astrophysics
Astrophysics
24
Faculae, Infrared Imagery, Photosphere, Solar Atmosphere, Sunspots, Brightness Temperature, Calcium, Plasma Temperature, Umbras
Scientific paper
Continuum observations at 1.63-microns using a PtSi IR CCD camera have yielded images of the deepest observable layers in an active region. When these are compared with spectroheliograms in visible continuum and in the Ca K wing, it becomes evident that faculae are seen near disk center as low-contrast, dark structures; also, the ratio of umbral intensity for small relative to large spots is substantially lower at 1.63 microns than in the red continuum. These findings suggest that, at the deepest observable layers, faculae as well as spots contain plasma which is cooler than the surrounding photosphere at equal optical depth; they can be explained straightforwardly if flux tubes of all diameters exhibit convective heat flow along their axes.
Foukal Peter
Little Roderick
Mooney J.
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