Heliospheric X-ray emission associated with charge transfer of the solar wind with interstellar neutrals

X-rays should be generated throughout the heliosphere as a consequence of charge transfer collisions between heavy (Z > 2) solar wind ions and interstellar neutrals. The high charge state solar wind ions resulting from these collisions are left in highly excited states and emit extreme ultraviolet or soft X-ray photons. This solar wind charge exchange mechanism applied to cometary neutrals has been used to explain the soft X-ray emission observed from comets. A simple model demonstrates that heliospheric X-ray emission can account for about 25%-50% of the observed soft X-ray background intensities. The spatial and temporal variations of heliospheric X-ray emission should reflect variations in the solar wind flux and composition as well as variations in the distribution of interstellar neutrals within the heliosphere. The heliospheric X-ray background can perhaps be identified with the long-term enhancements in the soft X-ray background measured by ROSAT.