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| Titel |
Processes and mechanisms governing the initiation and propagation of CMEs |
| VerfasserIn |
B. Vršnak |
| 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.3089-3101 |
| Datensatznummer |
250016256
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| Publikation (Nr.) |
 copernicus.org/angeo-26-3089-2008.pdf |
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| Zusammenfassung |
| The most important observational characteristics of coronal mass ejections (CMEs) are summarized,
emphasizing those aspects which are relevant for testing physical concepts employed to explain the
CME take-off and propagation. In particular, the kinematics, scalings, and the CME-flare
relationship are stressed. Special attention is paid to 3-dimensional (3-D) topology of the
magnetic field structures, particularly to aspects related to the concept of semi-toroidal
flux-rope anchored at both ends in the dense photosphere and embedded in the coronal magnetic
arcade. Observations are compared with physical principles and concepts employed in explaining the
CME phenomenon, and implications are discussed. A simple flux-rope model is used to explain various
stages of the eruption. The model is able to reproduce all basic observational requirements: stable
equilibrium and possible oscillations around equilibrium, metastable state and possible
destabilization by an external disturbance, pre-eruptive gradual-rise until loss of equilibrium,
possibility of fallback events and failed eruptions, relationship between impulsiveness of the CME
acceleration and the source-region size, etc. However, it is shown that the purely ideal MHD
process cannot account for highest observed accelerations which can attain values up to
10 km s−2. Such accelerations can be achieved if the process of reconnection beneath the
erupting flux-rope is included into the model. Essentially, the role of reconnection is in changing
the magnetic flux associated with the flux-rope current and supplying "fresh" poloidal magnetic
flux to the rope. These effects help sustain the electric current flowing along the flux-rope, and
consequently, reinforce and prolong the CME acceleration. The model straightforwardly explains the
observed synchronization of the flare impulsive phase and the CME main-acceleration stage, as well
as the correlations between various CME and flare parameters. |
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