2007PASJ...59S.133F

We report an apparent detection of the C <FONT SIZE="-2">VI</FONT> 4p to 1s transition line at 459eV, during a long-term enhancement (LTE) in the Suzaku north ecliptic pole observation of 2005 September 2. The observed line intensity is comparable to that of the C <FONT SIZE="-2">VI</FONT> 2p to 1s line at 367eV. This is strong evidence for the charge-exchange process. In addition, O <FONT SIZE="-2">VII</FONT> , O <FONT SIZE="-2">VIII</FONT> , Ne <FONT SIZE="-2">X</FONT> , and Mg <FONT SIZE="-2">XI</FONT> lines showed clear enhancements. There are also features in the 750-900eV range that could be due to some combination of Fe L lines, higher order transitions of O <FONT SIZE="-2">VIII</FONT> (3p to 1s and 6p to 1s), and a Ne <FONT SIZE="-2">IX</FONT> line. From the correlation of the X-ray intensity with the solar-wind flux on time scales of about half a day, and from the short-term (∼10 minutes) variations of the X-ray intensity, these lines most likely arise from solar-wind heavy ions interacting with neutral material in the Earth's magnetosheath. A hard power-law component is also necessary to explain the LTE spectrum. Its origin is not yet known. Our results indicate that solar activity can significantly contaminate Suzaku cosmic X-ray spectra below ∼1 keV. Recommendations are provided for recognizing such contamination in observations of extended sources.