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Hot loop oscillations seen by SUMER: examples and statistics
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Tongjiang Wang Submitted: 2002-07-04 04:02
We measure physical parameters of Doppler-shift oscillations
in 17 flare-like events. These events have been recorded by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on SOHO, along a slit fixed above limb active regions. The selected spectral windows contain emission lines with formation temperatures from 10^4 to 10^7 K. The events were only detected in hot flare lines, without any signature in lines formed around 2 X 10^6 K. Similarly, the Doppler shift oscillations occur in regions coincident with hot soft X-ray loops, but not with EUV loops. The oscillations have periods of 11-31 min, with an
exponential decay time of 5.5-29 min, and show an initial large shift pulse with peak velocities up to 200 km/s. Several indications suggest that the Doppler oscillations are incompressible coronal loop oscillations,
that are usually excited impulsively by weak flare (or microflare) events that also produced a strong emission increase at 5-8 X 10^6 K.
Authors: T. J. Wang, S. K. Solanki, W. Curdt, D. E. Innes, and I. E. Dammasch
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Publication Status: IAU-188 Proceedings, Santorini, June 11-15, 2002 (ESA SP-505), p199
Last Modified: 2003-02-18 02:11
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