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Acceleration of Coronal Mass Ejections

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James Chen

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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