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Paper: SUMER Observations of Intensity Oscillations in the Transition Region of a Sunspot
Volume: 184, Third Advances in Solar Physics Euroconference: Magnetic Fields and Oscillations
Page: 271
Authors: Rendtel, J.; Staude, J.; Innes, D. E.; Wilhelm, K.
Abstract: UV spectroscopic data obtained with the SUMER spectrograph aboard SOHO have been analysed to detect oscillations in the chromosphere-corona transition region (TR) above sunspots. We observed the active region NOAA 7986 in the wavelength bands around the Ne VIII line at 770.4 Å and the C IV line at 1548.1 Å on August 29, 1996, between 09:08 UT and 13:31 UT. Simultaneous observations with the Normal Incidence Spectrometer of CDS aboard SOHO have shown, that the spot had a bright EUV plume at TR temperatures. A preliminary data analysis indicates intensity oscillations in the 2-minute range (7.3...7.9 mHz) in both spectral lines. The temporal variation of oscillatory power in the two spectral lines is generally in opposite directions, i.e. during an increase of oscillatory power in the Ne VIII line we find a decrease in the C IV line. A similar but smaller tendency is observed in the average intensity of the line profiles. This hints at a non-adiabatic behaviour of the oscillations and a slow cooling of the emitting sunspot plume region.
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