Rosat and XMM-Newton observations of solar wind charge exchange with neutral atoms

High charge state solar wind ions charge exchanging with neutral gas create soft X-rays, a phenomenon first observed as X-ray emission from comets. Here, we present two examples of how the X-ray products of these charge exchange reactions may be used to probe the near Earth distribution of neutral gas. The first is a series of four XMM-Newton observations of the Hubble Deep Field North. The initial three exposures were statistically consistent with each other while the fourth, which coincided with a significant increase in the solar wind flux, showed a strong enhancement at energies less than 1.4 keV, which was dominated by line emission. Data from the Low Energy Neutral Atom imager on the IMAGE spacecraft inside the Earth's magnetosphere during this event show Sun signal brightening indicating enhanced solar wind charge exchange was occurring at this time. The second is the long-term trending of the ROSAT All-Sky Survey data which shows an enhancement in early December consistent with where the downstream helium focusing cone is expected. However, the distribution is shifted toward higher ecliptic longitudes than the expected downstream direction and appears to exhibit a two-peak structure.