Synthetic Spectra of Cometary X-ray Emission from Solar Wind Charge Transfer

W.-H. Ip (Max-Planck-Inst. fuer Aeronomie), D.E. Shemansky (Dept. Aerospace Engineering, USC)

The recent detection of strong X-ray emission in the comas of several comets by the German X-ray satellite, ROSAT, has been interpreted in terms of collisional excitation of the solar wind heavy ions via charge transfer interaction with the neutral comas (T.E. Cravens, GRL, 24, 104, 1996). This theoretical model can be tested by the computation of emission spectra to be expected in a cometary coma. An accurate prediction of the emission spectrum requires development of atomic models because of the multiple cascade transitions that take place from electrons captured into high principal quantum number (n) states. Atomic models have been developed for HeII, OVI, OVII, OVIII and several other major heavy ion species. Many of the species produce emission at wavelengths longward of 1000 A and are accessible to telescope systems such as HST. Synthetic spectra of cometary X-ray and EUV emissions under different solar wind conditions will be constructed and compared with the ROSAT observations.