Other
Scientific paper
Dec 1976
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1976apj...210..836c&link_type=abstract
Astrophysical Journal, vol. 210, Dec. 15, 1976, pt. 1, p. 836, 837, 839-842.
Other
36
Far Ultraviolet Radiation, Line Spectra, Solar Spectra, Spectrum Analysis, Sunspots, Ultraviolet Spectra, Chromosphere, Emission Spectra, Magnetoacoustic Waves, Magnetohydrodynamic Waves, Solar Corona, Spectral Line Width
Scientific paper
The emission-line spectrum between 1200 and 1817 A from a sunspot in McMath region 12510 near the solar center is discussed. The spectrum was obtained by the normal-incidence spectrograph on Skylab. The principal results are: (1) the widths of emission lines originating in the chromosphere and lower transition region over the sunspot are much narrower than those previously reported for a polar coronal hole observed above the limb and a quiet chromospheric network observed near the solar center, indicating that the mass motions in the sunspot are less than in these other regions; (2) the sunspot spectrum, aside from the narrow widths of emission lines, is similar to spectra from the chromospheric network boundary. The intensities of lines in the sunspot are much enhanced relative to the network interior. From the full-width at half-maximum of the 1207-A Si III line, an optical depth at line center of 3.6 is deduced. Comparison with Parker's (1974) theory of sunspots shows that, if the enhancement of emission lines is due to enhanced transport of hydromagnetic waves generated in the sunspot convective zone, the mode of the waves is predominately Alfvenic.
Cheng Chung-Chieh
Doschek George A.
Feldman Uri
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