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.
Highlights
X-ray and extreme-ultraviolet (EUV) radiation has been observed from more than a dozen comets (Lisse et al 1996, 1999a, 1999b; Dennerl, Englhauser, & Trumper 1997; Mumma, Krasnopolsky, & Abbott 1997; Krasnopolsky et al 1997; Owens et al 1998; Krasnopolsky, Mumma, & Abbott 2000; Krasnopolsky & Mumma 2001)
If the charge transfer mechanism dominates the excitation, with sufficient spectral resolution the composition of the solar wind can be inferred from a comparison of the observed spectra with the spectra predicted from charge transfer (Dennerl et al 1997; Kharchenko & Dalgarno 2000; Schwadron & Cravens 2000)
The low-resolution spectra and the total intensities of X-ray and EUV emissions detected from comets are reproduced by calculations with typical ion compositions of the solar wind
Summary
X-ray and extreme-ultraviolet (EUV) radiation has been observed from more than a dozen comets (Lisse et al 1996, 1999a, 1999b; Dennerl, Englhauser, & Trumper 1997; Mumma, Krasnopolsky, & Abbott 1997; Krasnopolsky et al 1997; Owens et al 1998; Krasnopolsky, Mumma, & Abbott 2000; Krasnopolsky & Mumma 2001). If the charge transfer mechanism dominates the excitation, with sufficient spectral resolution the composition of the solar wind can be inferred from a comparison of the observed spectra with the spectra predicted from charge transfer (Dennerl et al 1997; Kharchenko & Dalgarno 2000; Schwadron & Cravens 2000). A model spectrum based on the assumptions that the solar wind ions behave as hydrogenic systems and only allowed radiative transitions occur has been constructed by Schwadron & Cravens (2000). They incorporate the contributions from the impacts of the fast solar wind and the slow solar wind that have different ion compositions. We demonstrate that forbidden transitions give rise to intense emission lines, which, because of the long lifetimes of metastable states, are absent from laboratory beam spectra (Suraud et al 1991; Greenwood et al 2000)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
