DOI: 10.1051/0004-6361:20064942
Letter
Large amplitude oscillation of a polar crown filament in the pre-eruption phase
H. Isobe1, 2 and D. Tripathi11 Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
e-mail: [D.H.Isobe;D.Tripathi]@damtp.cam.ac.uk
2 Department of Earth and Planetary Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
e-mail: isobe@eps.s.u-tokyo.ac.jp
(Received 31 January 2006 / Accepted 10 February 2006)
Abstract
Aims.We report observation of a large-amplitude filament oscillation
followed by an eruption. This is used to probe the pre-eruption condition
and the trigger mechanism of solar eruptions.
Methods.We used the EUV images from the Extreme-Ultraviolet Imaging Telescope on board
SOHO satellite and the H
images from the Flare Monitoring Telescope
at Hida Observatory. The observed event is a polar crown filament that
erupted on 15 Oct. 2002.
Results.The filament clearly exhibited oscillatory motion in the slow-rising,
pre-eruption phase.
The amplitude of the oscillation was larger than 20 km s-1,
and the motion was predominantly horizontal. The period was
about 2 h and seemed to increase during the oscillation, indicating
weakening of restoring force.
Conclusions.Even in the slow-rise phase before the eruption, the filament retained
equilibrium and behaved as an oscillator, and the equilibrium is
stable to nonlinear perturbation.
The transition from such nonlinear stability to either
instabilities or a loss of equilibrium that leads to the eruption occurred
in the Alfvén time scale (~1 h). This suggests that
the onset of the eruption was triggered by a fast magnetic reconnection
that destabilized the pre-eruption magnetic configuration, rather
than by the slow shearing motion at the photosphere.
Key words: Sun: corona -- Sun: coronal mass ejections (CMEs) -- Sun: prominences -- Sun: filaments
© ESO 2006
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