Detection of ultra-long-period oscillations in an EUV filament

Free access article

Issue		A&A Volume 427, Number 1, November III 2004


Page(s)		L5 - L8
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:200400083

A&A 427, L5-L8 (2004)
DOI: 10.1051/0004-6361:200400083

Letter

Detection of ultra-long-period oscillations in an EUV filament

C. Foullon, E. Verwichte and V. M. Nakariakov

Department of Physics, University of Warwick, Coventry CV4 7AL, UK
e-mail: foullonc@astro.warwick.ac.uk

(Received 23 June 2004 / Accepted 22 September 2004)

Abstract
We report the first detection of long-period (8-27 h) oscillatory intensity variations in a coronal filament. The filament is observed continuously as it crosses the solar disk in a 12-min-cadence SoHO/EIT 195 Å uninterrupted data set. Cyclic intensity variations are found to be correlated along the filament, while the most pronounced oscillations are detected at its southern end for nearly 6 days. The dominant period of these oscillations is 12.1 h and the amplitude of the intensity variations reaches approximately 10% of the background intensity. The ultra-long-period oscillations may be interpreted in terms of slow string MHD modes or may be connected with thermal over-stability associated with peculiarities of the cooling/heating function and with the effect of neutrals. These theoretical predictions however do not explain the spatial structure of the oscillations along the filament.

Key words: Sun: prominences -- filaments -- oscillations -- UV radiation

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