Evidence for solar-wind charge-exchange X-ray emission from the earth's magnetosheath

Abstract

During the Suzaku north ecliptic pole observation of 2005 September 2-4, a long-term enhancement was observed, and the C VI 4p to 1s transition line at 459 eV was apparently detected. The observed line intensity is comparable to that of the C VI 2p to 1s line at 367 eV. This is strong evidence for the charge-exchange process. In addition, O VII, O VIII, Ne X, and Mg XI lines showed clear enhancements. There are also features in the 750-900 eV range that could be due to some combination of Fe-L lines, higher order transitions of O VIII (3p to 1s and 6p to 1s), and a Ne IX line. From the correlation of the X-ray intensity with 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.