Heliospheric and Cometary X-rays Induced by the Solar Wind

The collisional interaction between Solar Wind (SW) ions and neutral interstellar, planetary, and cometary gases is reviewed. The charge-transfer mechanism of X-ray and Extreme Ultraviolet (EUV) emission of highly charged SW ions is described in detail. Emission spectra of individual SW ions are constructed using results of recent laboratory measurements and quantal calculations. The unique spectra of cascading photons arising in charge-transfer collisions between heavy SW ions and neutral atoms or molecules are discussed. The synthetic spectra of the charge-transfer EUV and X-ray emission are introduced for the SW plasma interacting with the cometary and interstellar gases. The spatial brightness distribution, total luminosity, and relative intensities of various spectral lines are calculated for the slow and fast solar wind. Results of spectral modeling are compared with observational data from ROSAT, EUVE, FUSE, and the Chandra X-ray telescope. Spectra of X-rays are predicted for Coronal Mass Ejections interacting with the neutral cometary, heliospheric, and atmospheric gases. New opportunities, based on analysis of the charge-transfer emission, are discussed for remote diagnostic of the interaction between the SW plasma and interstellar gas. The work on modeling spectra of the heliospheric X-ray and EUV emission is supported by the OSS NASA grant NNG04GD57G.