MODELING OF COMETARY X-RAYS CAUSED BY SOLAR-WIND MINOR IONS

X-ray emission was discovered in comet Hyakutake (C/1996 B2) by the Ro ntgen satellite in 1996, and these emissions were attributed to the ex citation of high charge state solar wind ions due to electron capture from cometary molecules or atoms. Using the plasma flow in the coma of Hyakutake calculated by a three-dimensional adaptive magneto-hydrodyn amic model, the density distribution of solar wind ions in the coma an d the resulting x-ray emission were computed. The calculated High Reso lution imager count rate of 4.4 per second and the spatial distributio n of the x-ray emission agree with the observations. A detailed energy spectrum of cometary x-rays is predicted in the 80 to 2000 electronvo lt energy range. Cometary x-rays present a sensitive tool to monitor c ometary activity and solar wind ion composition.