Possible Solar Wind Charge Exchange Emission from a Coronal Mass Ejection

Abstract

We compare shadowing observations of the soft X‐ray background (SXRB) carried out with XMM‐Newton and Suzaku. We find that the XMM‐Newton spectra are strongly contaminated by solar wind charge exchange (SWCX) emission. This contamination was not taken into account in the original XMM‐Newton analysis, because solar wind data from ACE, which was expected to be a good diagnostic of SWCX, suggested that the spectra were unlikely to be contaminated by SWCX emission from the vicinity of the Earth. The increased SWCX emission in the XMM‐Newton spectra can be only partially attributed to variations in the large‐scale structure of the solar wind during the solar cycle. Heliospheric SWCX models underpredict the amount of SWCX seen in the XMM‐Newton spectra, suggesting that there may be additional SWCX contamination, possibly from a coronal mass ejection moving across the line of sight. These results imply that inspecting data from satellites that monitor the solar wind in the vicinity of the Earth may not be suffic...