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High-resolution spectra of solar magnetic features. II - Magnetic fields of umbral brightenings
Lites, Bruce W.; Bida, Thomas A.; Johannesson, A.; Scharmer, G. B.
AA(High Altitude Observatory, Boulder, CO), AB(High Altitude Observatory, Boulder, CO), AC(Lund Observatory, Sweden), AD(Royal Swedish Academy of Sciences, Stockholm, Sweden)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 373, June 1, 1991, p. 683-694. Research supported by NASA and Perkin Fund. (ApJ Homepage)
Publication Date:
Solar Physics
NASA/STI Keywords:
Limb Brightening, Magnetic Field Configurations, Solar Magnetic Field, Spectral Resolution, Umbras, Convection Currents, Image Processing, Magnetic Flux, Radiation Transport, Sunspots, Zeeman Effect
Bibliographic Code:


The spectra of Fe I and Fe II Zeeman-sensitive lines enhanced by video processing of CCD images are considered. The magnetic-field variation within umbras is obtained from the nearly complete Zeeman splitting of the Stokes I profile. It is shown that small brightenings within umbrae have magnetic fields nearly equal to or slightly smaller than that of the darker surroundings; these features are also nearly at rest with respect to their surroundings. It is noted that the absence of significant motions in umbral dots implies that radiation transports most of the energy at and immediately below the surface. The small size of the dots implies that, if convective plumes transport energy below the surface of sunspot umbrae, they should have both a lateral extent and a depth of their upper boundary comparable to or smaller than the size of the dot.

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