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| Titel |
Why are CMEs large-scale coronal events: nature or nurture? |
| VerfasserIn |
L. Driel-Gesztelyi, G. D. R. Attrill, P. Demoulin, C. H. Mandrini, L. K. Harra |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 26, no. 10 ; Nr. 26, no. 10 (2008-10-15), S.3077-3088 |
| Datensatznummer |
250016255
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| Publikation (Nr.) |
 copernicus.org/angeo-26-3077-2008.pdf |
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| Zusammenfassung |
| The apparent contradiction between small-scale source regions of, and
large-scale coronal response to, coronal mass ejections (CMEs) has been a
long-standing puzzle. For some, CMEs are considered to be inherently
large-scale events – eruptions in which a number of flux systems participate
in an unspecified manner, while others consider magnetic reconnection in
special global topologies to be responsible for the large-scale response of
the lower corona to CME events. Some of these ideas may indeed be correct in
specific cases. However, what is the key element which makes CMEs
large-scale? Observations show that the extent of the coronal disturbance
matches the angular width of the CME – an important clue, which does not
feature strongly in any of the above suggestions. We review observational
evidence for the large-scale nature of CME source regions and find them
lacking. Then we compare different ideas regarding how CMEs evolve to
become large-scale. The large-scale magnetic topology plays an important role
in this process. There is amounting evidence, however, that the key process
is magnetic reconnection between the CME and other magnetic structures.
We outline a CME evolution model, which is able to account for all the key
observational signatures of large-scale CMEs and presents a clear picture
how large portions of the Sun become constituents of the CME. In this
model reconnection is driven by the expansion of the CME core resulting
from an over-pressure relative to the pressure in the CME's surroundings.
This implies that the extent of the lower coronal signatures match the final
angular width of the CME. |
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