  White-light observations of the solar corona show that there are two
characteristic types of Coronal Mass Ejections (CMEs) in terms of speed-height
profiles: so-called fast CMEs that attain high speeds low in the corona and
slow CMEs that gradually accelerate from low initial speeds. Low and Zhang
(2002) have recently proposed that fast and slow CMEs result from initial
states with magnetic configurations characterized by normal prominences (NPs)
and inverse prominences (IPs), respectively. To test their theory, we employed
a two-dimensional, time-dependent, resistive magnetohydrodynamic code to
simulate the expulsion of CMEs in these two different prominence environments.
Our numerical simulations demonstrate that (i) a CME-like expulsion is more
readily produced in an NP than in an IP environment, and, (ii) a CME
originating from an NP environment tends to have a higher speed early in the
event than one originating from an IP environment. Magnetic reconnection plays
distinct roles in the two different field topologies of these two environments
to produce their characteristic CME speed-height profiles. Our numerical
simulations support the proposal of Low and Zhang (2002) although the
reconnection development for the NP associated CME is different from the one
sketched in their theory. Observational implications of our simulations are
discussed.
