Acceleration of Coronal Mass Ejections

James Chen

Abstract

A recent series of theory-observation comparison studies [1, 2, 3] show that a significant subset of LASCO CMEs can be explained as expanding magnetic flux ropes driven away from their initial positions by emergence or injection of magnetic flux.  Using the new theoretical model, we revisit a number of previous observational findings that have not been explained.  In this paper, we address the finding that both flare- and eruptive prominence-associated CMEs, the greatest acceleration occurs within 2--3 Rs of the Sun [4]. We address two significant questions raised by this observation: (1) why the main acceleration process occurs very close to the Sun and (2) what determines the height (i.e., 2--3 Rs) beyond which impulsive acceleration does not occur.  The answer lies in the fact that a CME is a 3-D structure with a finite size and a finite magnetic field energy. We discuss the basic physics of the forces acting on CMEs.

[1] J. Chen et al., ApJ Lett., 490, L191, 1997

[2] J. Chen et al., ApJ, March, 2000

[3] J. Krall et al., in prepagation, 2000

[4] R. M. MacQueen and R. R. Fisher, ApJ, 254, 335, 1982
 

  Organization: Naval Research Laboratory
     Telephone: 202-767-3134
           Fax: 202-767-0631
        e-mail: chen@ppdchen.nrl.navy.mil
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   Washington, DC 20375