Implications of solar wind composition for cometary X-rays

Solar wind composition provides a strong source of variability for cometary X-rays. Using recently constrained composition observations from the Solar Wind Ion Composition Spectrometer on the Ulysses spacecraft (SWICS/Ulysses ) and information on ion-neutral charge-transfer collisions, we model comet ary X-ray emission and its variability. Fast and slow solar wind cases are adopted and compared to observations of X-ray spectra from the Rontgen-Sate llit (ROSAT) for comet Levy. The predicted and observed spectra compare mos t favorably for fast solar wind in optically thin conditions. Solar wind co mposition can be predicted as a function of the coronal temperature near it s source and, consequently, cometary X-ray spectra may be predicted as a fu nction of the solar wind's coronal temperature. Implications and additional developments necessary to unravel the compositional information contained in X-ray spectra are explored.