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We review results from spectroscopic observations of sunspot plumes obtained by the SOHO spectrographs CDS and SUMER in the vacuum UV wavelength range.
The solar atmosphere above sunspots is entirely different compared to other parts of the solar surface and exhibits some peculiarities. The transition region, which is normally a thin layer extends very high in altitude above sunspots and is filled by rather cool, low-density plasma.
Despite its low density and its cool transition region temperatures a high emission measure is observed in some emission lines. It is unclear, whether this is related to the strong, unipolar magnetic field in quasi-open magnetic field lines above sunspots. Sunspot plumes are sites of systematic downflow into a bottom layer, which is coherently oscillating with a 3-minute period. |
