2010MNRAS.402..867C

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 localized 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 is consistent with SWCX resulting from a passing CME. Highly ionized 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 Advanced Composition Explorer and Wind which measured an intense increase in the solar wind flux due to a CME that had been released from the Sun 2 d previous to the XMM-Newton observation.