  We present the analysis of an observation by XMM-Newton that exhibits
strongly variable, low-energy diffuse X-ray line emission. We reason that this
emission is due to localised solar wind charge exchange (SWCX), originating
from a passing cloud of plasma associated with a Coronal Mass Ejection (CME)
interacting with neutrals in the Earth's exosphere. This case of SWCX exhibits
a much richer emission line spectrum in comparison with previous examples of
geocoronal SWCX or in interplanetary space. We show that emission from OVIII is
very prominent in the SWCX spectrum. The observed flux from oxygen ions of 18.9
keV cm-2 s-1 sr-1 is consistent with SWCX resulting from a passing CME. Highly
ionised silicon is also observed in the spectrum, and the presence of highly
charged iron is an additional spectral indicator that we are observing emission
from a CME. We argue that this is the same event detected by the solar wind
monitors ACE and Wind which measured an intense increase in the solar wind flux
due to a CME that had been released from the Sun two days previous to the
XMM-Newton observation.
