  The relative importance of different initiation mechanisms for coronal mass
ejections (CMEs) on the Sun is uncertain. One possible mechanism is the loss of
equilibrium of coronal magnetic flux ropes formed gradually by large-scale
surface motions. In this paper, the locations of flux rope ejections in a
recently-developed quasi-static global evolution model are compared with
observed CME source locations over a 4.5-month period in 1999. Using EUV data,
the low-coronal source locations are determined unambiguously for 98 out of 330
CMEs. Despite the incomplete observations, positive correlation (with
coefficient up to 0.49) is found between the distributions of observed and
simulated ejections, but only when binned into periods of one month or longer.
This binning timescale corresponds to the time interval at which magnetogram
data are assimilated into the coronal simulations, and the correlation arises
primarily from the large-scale surface magnetic field distribution; only a weak
dependence is found on the magnetic helicity imparted to the emerging active
regions. The simulations are limited in two main ways: they produce fewer
ejections, and they do not reproduce the strong clustering of observed CME
sources into active regions. Due to this clustering, the horizontal gradient of
radial photospheric magnetic field is better correlated with the observed CME
source distribution (coefficient 0.67). Our results suggest that, while the
gradual formation of magnetic flux ropes over weeks can account for many
observed CMEs, especially at higher latitudes, there exists a second class of
CMEs (at least half) for which dynamic active region flux emergence on shorter
timescales must be the dominant factor.
