A Statistical Study of Two Classes of CMEs
Yong-Jae Moon Submitted: 2002-08-07 21:42
A comprehensive statistical study is performed to address the question
whether two classes of coronal mass ejections (CMEs) exist.
A total of 3217 CME events observed
by SOHO/LASCO in 1996 to 2000 have been analyzed.
We have examined the distributions of CMEs according
to speed and acceleration, respectively, and
investigated the correlation
between speed and acceleration of CMEs. This
statistical analysis is conducted for two
subsets containing those CMEs which show
a temporal and spatial association
either with GOES X-ray solar flares or with
%The number of CMEs in deceleration is comparable to the
%number of CMEs in acceleration.
We have found that
CMEs associated with flares have a higher median
speed than those associated with eruptive filaments and that
the median speed of CMEs
associated with strong flares is higher than that
of weak-flare-associated CMEs.
The distribution of CME acceleration shows a conspicuous
peak near zero, not only for the whole data set, but also
for the two subsets associated either with
solar flares or with eruptive filaments.
However, we have confirmed that
the CMEs associated with major flares tend to be more decelerated
than the CMEs related to eruptive filaments.
The fraction of flare-associated CMEs has a tendency to increase with the CME speed,
whereas the fraction of eruptive-filament-associated CMEs tends
with the CME speed.
This result supports the concept of two CME classes.
We have found a possibility of two components in the CME speed distribution
for both the CME data associated with flares larger than M1 class
and the CME data related with limb flares.
Our results suggest that the apparent single-peak distribution
of CME speed can be attributed to the projection effect and
possibly to abundance of small flares too.
We also note that there is a possible correlation
between the speed of CMEs and the time-integrated X-ray flux
of the CME-associated limb flares.
Authors: Moon, Y.-J., Choe, G.S., Wang, H., Park, Y.D., Gopalswamy, N., Yang, G., Yashiro, S.
Publication Status: ApJ, in press
Last Modified: 2002-08-07 21:49