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Paper: Transition Region Variability: Evidence for Oscillation
Volume: 154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop
Page: 798
Authors: O'Shea, E.; Doyle, J. G.
Abstract: The data reported here was obtained with the Coronal Diagnostic Spectrometer (CDS) in a sit-and-stare mode using a 4 x 240 arcsec slit. Using integration times ranging from 15 to 20 sec, two different types of observing sequences were obtained, the first involved the observation of three oxygen lines due to O 3 599 AA, O 4 554 AA and O 5 630 AA. These lines have temperature of formation ranging from 100,000 K to 250,000 K. The second type of sequence involved four lines, He 1 584 AA formed below 100,000 K, O 4 554 AA and O 5 630 AA formed between 150,000 K to 250,000 K, and Mg 10 610 AA formed at 1,000,000 K. Using a FFT technique, the resulting power spectra reveals periods ranging from 4 to 10 minutes for plasma around the 150,000 to 250,000 K region. These periods were present for ~40 minutes covering a region of ~7 arcsec^2. Excess power was present below 5 mHz in most datasets in He 1 line data. For about 10-15% of the slit a single period was detected. No periods were found in the Mg 10 line, although this may be related to the fact that Mg 10 was rather weak in our data.
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