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Letter to the Editor
Intensity oscillations in a sunspot plume
Received 26 February 1999 / Accepted 12 March 1999
Observations of a sunspot plume (a compact feature, bright in the transition region line of O V 629.7 Å at K), seen above a sunspot in the active region AR8249, have been made with a 15-second time resolution with the Coronal Diagnostic Spectrometer on SOHO. Intensity of the O V 629.7 Å line in the sunspot plume oscillates with an amplitude of up to ten percent and periods of 167 and 182 seconds. The same oscillations are also seen in the Ne IV 543.9 Å, Ne V 572.4 Å and Ne VI 562.8 Å lines ( K) but with a lower signal-to-noise ratio. Inspection of data for several other sunspots shows that all sunspot plumes show the intensity oscillations of the O V 629.7 Å line and other transition region lines in the K temperature range.
Key words: Sun: oscillations Sun: sunspots Sun: transition region Sun: UV radiation
© European Southern Observatory (ESO) 1999
Online publication: March 29, 1999