HR: 08:20h
AN: SH21A-02 INVITED     [PDF]
TI: Acceleration of CMEs: A Diagnostic for Driving Mechanisms?
AU: * Chen, J
EM: chen@ppd.nrl.navy.mil
AF: Plasma Physics Division, Naval Research Laboratory, Code 6790, 4555 Overlook Avenue, SW, Washington, DC 20375 United States
AB: Typical coronal mass ejections (CMEs) undergo the bulk of their acceleration low in the corona. Theoretical analysis based on a three-dimensional flux-rope geometry [1] shows that CME acceleration profiles exhibit a universal scaling law characterized by the critical scale height $Z_* \equiv S_f/2$, where $S_f$ is the separation distance between the two stationary footpoints of the flux rope. Specifically, maximum acceleration is attained shortly after the apex of the flux rope reaches height $Z_*$ from the solar surface, and the acceleration is subsequently reduced to about 1/4 of the peak value when the apex reaches height $Z_m \simeq 3 Z_*$. This means that the observed acceleration profile in the low corona can directly yield information on the geometrical size of the flux rope, i.e., $S_f$. The $S_f$ scaling is applicable regardless of the eruption speed so long as the pre-eruption structure is a flux rope or becomes one early enough in the eruption process. The scaling law has been tested against observed CMEs using TRACE, C1, C2, and C3 data, with good quantitative agreement, and is consistent with a recent simulation of a 3-D flux rope [2]. We discuss the observational implications of these results with respect to various proposed CME models and driving mechanisms. \bigskip \noindent [1] Chen, J., and J. Krall, Acceleration of coronal mass ejections, {\it J. Geophys. Res.}, in press, 2003 \noindent [2] Roussev, I. I., et al., {\it Astrophys. J.}, {\it 588}, L45, 2003. \bigskip \noindent Work supported by ONR and NASA
DE: 7513 Coronal mass ejections
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting