Solar wind charge exchange: an astrophysical nuisance

Solar wind charge-exchange (SWCX) emission is present in every X-ray observation of an astrophysical object. The emission is problematic when one cannot remove the foreground by the simultaneous measurement of a nearby field. SWCX emission is a serious impediment to the study of the diffuse hot ISM, including the galactic halo, as its contribution to diagnostic emission lines is temporally variable. Modeling the SWCX emission, in order to remove it from our observations, has proven to be more difficult than originally anticipated. This work reviews our current understanding of SWCX emission, with special attention to all the components required for future modeling tools. Since, in the absence of such a tool, observing programs can still be constructed to minimize the effect of SWCX, mitigation strategies are discussed. Although some aspects of SWCX will be very difficult to characterize, progress continues on many fronts.