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Physical and Morphological Properties of CMEs
Russell A. Howard
Our understanding of the expulsion of coronal material has improved dramatically
since the launch of SOHO. LASCO has observed small scale outflow
in streamers, larger scale ejecta which are the counterpart of the chromospheric
surge as well as the large scale coronal mass ejection. We would
like to restrict the definition of a CME to this larger scale process,
which appears to be arising from different mechanisms. We will concentrate
on the CME results here and give an overview of our current understanding
of CMEs - their physical and morphologic properties. The kinematic
properties are quite similar to previous epochs. There are some major
differences however. One is in the speed and acceleration profiles.
While the average speeds are about the same as previously, acceleration
and even deceleration are observed in a significant number of events. The
number of concave outward events is about 1/3 of all LASCO CMEs. These
events had been thought to be evidence for disconnection but are now interpreted
as "flux rope" events, and are the counterpart of the magnetic clouds seen
in the solar wind. We interpret these flux rope events as eruptions
of large-scale streamers overlying a neutral line. Trailing the CME front
can be complex small-scale features, which may contain cool material. Utilizing
radio emission, we have been able to associate the location of a shock
with the leading edge of the CME.
Authors: R.A. Howard, O.C. St. Cyr, S.P. Plunkett, K.P. Dere,
Telephone: (202) 767-3137
Address: Code 7660
Naval Research Laboratory
Washington DC 20375
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