A benchmark event sequence for mass ejection onset studies

Free access article

Issue		A&A Volume 461, Number 3, January III 2007


Page(s)		1155 - 1162
Section		The Sun
DOI		http://dx.doi.org/10.1051/0004-6361:20066100

A&A 461, 1155-1162 (2007)
DOI: 10.1051/0004-6361:20066100

A flare associated CME with coronal dimming, ascending pre-flare loops and a transient cool loop

R. A. Harrison and D. Bewsher

Space Science and Technology Department, CCLRC/Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
e-mail: d.bewsher@rl.ac.uk

(Received 25 July 2006 / Accepted 11 October 2006)

Abstract
Aims.In this study, we report on the spectroscopic observations of a particularly well-observed flare and coronal mass ejection (CME) event sequence which we feel can be used as a benchmark study for CME onsets.
Methods.Specifically, we report on a set of extreme-ultraviolet (EUV) spectroscopic observations using the Solar and Heliospheric Observatory (SOHO) to determine features of the CME onset process revealed through the analysis of plasma at different temperatures.
Results.The flare which occurred on the north-western limb was associated with a large CME. The event in question showed evidence for pre-flare ascending loops containing 1-2 million K plasma, which disappeared just prior to the flare. This disappearance is interpreted as coronal dimming, and it appears to coincide with the projected mass ejection onset time. In addition, a discrete, short-lived coronal loop containing plasma at transition region temperatures was detected just prior to this eruption. This loop displayed mass motion, along flux tubes, with oppositely directed flows. The nature and timing of this transient loop suggest a close relationship between it and the eruption process. Examinations of the timing and topology, which extend previous studies considerably, are found to be consistent with the mass ejection onset interpretation of Zhang and co-workers.
Conclusions.The clarity of this event sequence suggests that we should regard it as a benchmark in studies of the mass ejection onset process.

Key words: Sun: coronal mass ejections (CMEs) -- Sun: flares -- Sun: corona -- Sun: UV radiation

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