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Issue A&A Volume 402, Number 2, May I 2003 Page(s) L17 - L20 Section Letters DOI 10.1051/0004-6361:20030448

A&A 402, L17-L20 (2003)
DOI: 10.1051/0004-6361:20030448

Letter

Slow-mode standing waves observed by SUMER in hot coronal loops

T. J. Wang, S. K. Solanki, D. E. Innes, W. Curdt and E. Marsch

Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany
(Received 12 March 2003 / Accepted 25 March 2003)

Abstract
We report the first detection of postflare loop oscillations seen in both Doppler shift and intensity. The observations were recorded in an  line by the SUMER spectrometer on SOHO in the corona about 70 min after an M-class flare on the solar limb. The oscillation has a period of about 17 min in both the Doppler velocity and the intensity, but their decay times are different (i.e., 37 min for the velocity and 21 min for the intensity). The fact that the velocity and the intensity oscillations have exactly a 1/4-period phase difference points to the existence of slow-mode standing waves in the oscillating loop. This interpretation is also supported by two other pieces of evidence: (1) the wave period and (2) the amplitude relationship between the intensity and velocity are as expected for a slow-mode standing wave.

Key words: Sun: corona -- flares -- oscillations -- UV radiation

Offprint request: T. J. Wang, wangtj@linmpi.mpg.de

© ESO 2003

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