The Heliospheric Contribution to the Soft X-ray Background Emission

The soft X-ray background observed from Earth contains contributions not only from outside the solar system such as the local bubble but also contributions from within the solar system, including contributions from the interplanetary medium, from the terrestrial geocorona, and from the magnetosheath. Great effort was spent on removing non-cosmic contamination from data collected during the ROSAT all-sky survey. Some of the contamination is the X-ray emission produced from charge exchange of solar wind ions with interstellar and geocoronal neutral gas. The time-varying component of this contamination was removed for the ROSAT survey, but the steady-state component was not. In this chapter, we present ROSAT 1/4-keV and 3/4-keV band all-sky maps of the cosmic soft X-ray emission with the steady state heliospheric and geocoronal components removed via modeling procedures. These new determinations of the "true" cosmic background X-ray emission will allow a rc-interpretation of the nature of the local hot bubble. In particular, the thermal pressure of the bubble gas must be about a factor of two less than the pressures deduced from the original ROSAT all-sky survey.