Variability of Cometary X-Ray Emission Induced by Solar Wind Ions

Abstract

X-ray emission spectra induced by the interaction of the slow and fast solar wind components with cometary gas are calculated for typical solar wind compositions. The emission spectra arising from the charge transfer mechanism are shown to be in good agreement with observational data. The identities and intensities of the brightest spectral lines that include forbidden transitions are obtained for the slow and fast solar winds. Differences in emission spectra of individual comets occur because of variations in the solar wind composition. Comparisons with observational data for comets Levy and Hale-Bopp indicate that they were subjected to the slow solar wind. The spectra at photon energies above 500 eV fluctuate with the solar wind composition because of the varying presence of fully stripped oxygen ions. Mechanisms of X-ray photon emission at energies above 0.9 keV are discussed.