  The Ultraviolet Coronagraph Spectrometer on board the Solar and Heliospheric
Observatory (SOHO) often observes low ionization state coronal mass ejection
(CME) plasma at ultraviolet wavelengths. The CME plasmas are often detected in
O VI (3x10^5K), C III (8x10^4K), LyA, and LyB, with the low ionization plasma
confined to bright filaments or blobs that appear in small segments of the UVCS
slit. On the other hand, in situ observations by the Solar Wind Ion Composition
Spectrometer (SWICS) on board Advanced Composition Explorer (ACE) have shown
mostly high ionization state plasmas in the magnetic clouds in interplanetary
coronal mass ejections (ICME) events, while low ionization states are rarely
seen. In this analysis, we investigate whether the low ionization state CME
plasmas observed by UVCS occupy small enough fractions of the CME to be
consistent with the small fraction of ACE ICMEs that show low ionization
plasma, or whether the CME plasma must be further ionized after passing the
UVCS slit. To do this, we determine the covering factors of low ionization
state plasma for 10 CME events. We find that the low ionization state plasmas
in CMEs observed by UVCS show average covering factors below 10%. This
indicates that the lack of low ionization state ICME plasmas observed by the
ACE results from a small probability that the spacecraft passes through a
region of low ionization plasma. We also find that the low ionization state
plasma covering factors in faster CMEs are smaller than in slower CMEs.

Solar and Stellar Astrophysics