Authors: Wurz, P., Bochsler, P., and Lee, M. A.
Reference: Fall AGU 1999
For the coronal mass ejection (CME) of January 6, 1997, a strong element
fractionation of the heavy ions was observed with the SOHO/CELIAS/MTOF
instrument at 1 AU. During the passage of the CME plasma and the passage
of the erupted filament, which followed the CME, a mass-dependent element
fractionation was found, with a monotonic increase toward heavier
elements. Si/O and Fe/O ratios around 0.5 were observed. With a
theoretical model we can reproduce the observed element fractionation. The
model assumes hot coronal loops as the precursor of the CME. Diffusion
perpendicular to the magnetic field lines results in the preferential loss
of lighter ions in the loop, leading to mass fractionation. To
quantitatively reproduce the fractionation, the loops must have existed at
least seven days before they became part of the CME plasma, a time which
is commensurate with optical observations.