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Astron. Astrophys. 355, 725-742 (2000)


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Observation of the origin of CMEs in the low corona

C. Delannée  *  1, J.-P. Delaboudinière 1 and P. Lamy 2

1 Institut d'Astrophysique Spatiale, Université Paris Sud-CNRS, bat 121, 91405 Orsay, France
2 Laboratoire d'Astronomie Spatiale, Traverse du Siphon, Les Trois Lucs, 13012 Marseille, France

Received 9 December 1998 / Accepted 11 January 2000

Abstract

The aim of the main observing program with EIT on board SOHO, is to monitor the whole Sun surface in the Fe XII emission line at 195 Å, every 17 minutes. The very beginning of some CMEs can be observed. We interpret Fe XII images in conjunction with He II , H[FORMULA] and coronagraph observations over a period of 6 days. We find that 7 prominences produced ejections. An active region produced 9 ejections. Five ejections are seen as dark bubbles propagating above the solar limb while 9 are seen as dimmings on the solar surface. The 3 other ejections are bright bubbles observed rising up above the limb. Thirteen of the 17 observed ejections are related to a CME. Two CMEs of the 15 CMEs observed with LASCO C2 are not related to Fe XII low corona events. Probably, these CMEs have their origin behind the limb. Prominences give rise to quite slow CMEs, 50-120 km s-1 while fast CMEs, 110-1000 km s-1, originate close to active regions. We conclude that CMEs start in the low corona and that large scale coronal structures reconfigurations occur when these disturbances propagate outward.

Key words: Sun: activity – Sun: atmosphere – Sun: corona – Sun: particle emission – Sun: prominences

* Now present at Goddard Space Flight Center, SoHo EAF, mail code 682.3, Greenbelt, MD 20771 USA

© European Southern Observatory (ESO) 2000

Online publication: March 9, 2000

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