Physics
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmsh12a0741v&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #SH12A-0741
Physics
7513 Coronal Mass Ejections, 7531 Prominence Eruptions
Scientific paper
Basic features of coronal mass ejections (CMEs) are surveyed, relating the observations in chromospheric and transition region spectral lines with white light coronographic observations. The pre-eruptive prominence evolution, including the development of internal (helical) structure is emphasized. Various processes causing destabilization of the arcade/filament system are noted. Properties of the acceleration phase, including the relationship between the dynamics of prominence, cavity, and leading edge of CMEs are stressed revealing various acceleration scenarios. The decrease of the helical fine structure pitch angle and the mass leakage estimated in some prominences are presented as a function of time and compared with acceleration curves. The events showing a deceleration in late phases of cronographic observations are used to estimate the influence of the drag force on the flux rope motion and to evaluate the propelling Lorentz force. The CME velocities, earth transit times, and in situ measured velocities are analyzed to infer the intreplanetary dynamics of ejecta.\The observational features described are explained considering the Lorentz force acting in the line-tied semi-toroidal flux rope, the gravity, and the aerodynamic drag. At low heights (initial stage) dominant forces are the Lorentz force and gravity. After the ejection attains velocity in the order of 100 km s-1 the influence of the aerodynamic drag becomes important. Since the cold and dense prominence material is leaking down the rope's legs, and the height increases, the gravity soon becomes negligible. The Lorentz force also starts decreasing beyond radial distances of several solar radii. Its action might be enhanced and prolonged by effects of the reconnection below the rope (long duration flare association) and by the redistribution of twist into the expanded uppermost parts of the rope. At large distances the drag becomes the dominant force. Fast ejecta start decelerating, whereas those in which the Lorentz force was too weak and the ejection did not surpass the solar wind speed get an additional acceleration: In the interplanetary space ejecta asymptotically approach the wind velocity.
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