Solar transition region above sunspots

Abstract

We study the TR properties above sunspots and the surrounding plage regions, by analyzing several sunspot spectra obtained by SUMER in March 1999 and November 2006. We compare the SUMER spectra observed in the umbra, penumbra, plage, and sunspot plume regions. The Lyman line profiles averaged in each region are presented. For the sunspot observed in 2006, the electron densities, DEM, and filling factors of the TR plasma in the four regions are also investigated. The self-reversals of the Lyman line profiles are almost absent in umbral regions at different locations (heliocentric angle up to $49^{\circ }$) on the solar disk. In the sunspot plume, the Lyman lines are also not reversed, whilst the lower Lyman line profiles observed in the plage region are obviously reversed. The TR densities of the umbra and plume are similar and one order of magnitude lower than those of the plage and penumbra. The DEM curve of the sunspot plume exhibits a peak centered around $\log (T/\mathrm{K})\sim 5.45$, which exceeds the DEM of other regions by one to two orders of magnitude at these temperatures. We also find that more than 100 lines, which are very weak or not observed anywhere else on the Sun, are well observed by SUMER in the sunspot, especially in the sunspot plume. We suggest that the TR above sunspots is higher and probably more extended, and that the opacity of the hydrogen lines is much smaller above sunspots, as compared to the TR above plage regions. Our result indicates that the enhanced TR emission of the sunspot plume is very likely to be the result of a large filling factor. The strongly enhanced emission at TR temperatures and the reduced continuum make many normally weak TR lines stick out clearly in the spectra of sunspot plumes.

18 pages, 7 figures, 6 tables. Tables 5 & 6 will only appear online. The paper has been accepted by A&A

References in corpus (10)

• Ionization balance for optically thin plasmas: rate coefficients for all atoms and ions of the elements H to Ni
• Forward modeling of stellar coronae: from a 3D MHD model to synthetic EUV spectra
• Coronal heating through braiding of magnetic field lines
• The Ly-alpha profile and center-to-limb variation of the quiet Sun
• Sizes of transition-region structures in coronal holes and in the quiet Sun
• Hydrogen Lyman-alpha and Lyman-beta spectral radiance profiles in the quiet Sun
• The Ly<alpha> and Ly<beta> profiles in solar prominences and prominence fine structure
• SUMER observations of the inverse Evershed effect in the transition region above a sunspot
• Formation Heights of Extreme Ultraviolet Lines in an Active Region Derived by Correlation of Doppler Velocity and Magnetic Field
• SUMER-Hinode observations of microflares: excitation of molecular hydrogen

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