Authors: P. Wurz, R.F. Wimmer-Schweingruber, and P. Bochsler, A.B.
Galvin and F.M. Ipavich, G.
Gloeckler and T.H. Zurbuchen
Reference: AGU Fall Meeting, San Francisco, CA, USA, December 15-19,
2000.
Abstract:
We present a study of the elemental composition of a sub-set of coronal
mass
ejections,
namely events that have been identified of being of the magnetic cloud type
(MC). We used plasma data
from the SOHO and ACE missions and so far investigated the MCs of 1997 and
1998. The study covers the
proton, alpha, and heavy ion abundances. Considerable variations from event
to event exist with regard
to the density of the individual species with respect to regular "slow"
solar wind preceding the MC
plasma. However, for the heavy elements, which can be regarded as tracers
in the plasma, there is a
general trend that the heavier ions are enriched compared to the lighter
ions. This trend can be
explained by a theoretical model of the precursor plasma loops on the sun
before launch of the CME.
Proton and alpha particle abundances have to be regarded separately since
they represent the main
plasma.