The heliosphere is a bubble of hot gas in interstellar space stretching
from the Sun to greater than 100 Sun-Earth distances. It contains some
fraction of inflowing neutral interstellar hydrogen and helium atoms.
Highly charged positive ions emanate from the Sun in the solar wind and
impact the neutral material. The ions capture electrons from the atoms
into high excited states that radiate primarily in the soft X-ray
spectral region. The spectra provide information about the solar wind
composition and velocity and the distribution of atoms in the
heliosphere. The X-rays generated by the solar wind contribute to the
diffuse soft X-ray background. Similar processes occur in the interaction
of the solar wind ions with comets and with the extended exospheres of
the planets. We are engaged in theoretical efforts to predict the spectra
resulting from the collisions of the solar wind ions (recent references).
1. Koutroumpa, D., R. Lallement, V. Kharchenko, A. Dalgarno , R. Pepino,
V. Izmodenov, and E. Quemerais,
“ Charge-transfer induced EUV and soft X-ray emissions in the
heliosphere”, A&A, 460, 289 (2006).
2. Sasseen T. P. , M. Hurwitz, C. M. Lisse, V. Kharchenko, A. Dalgarno
“ A search of EUV emission from Comets with the Cosmic Hot Interstellar
Plasma Spectrometer (CHIPS)”, ApJ, 650, 451 (2006).
3. Kharchenko V., A. Dalgarno, D. Schultz, and P. Stancil, “Ion emission
spectra in the Jovian X-ray Aurora”, Geophys. Res. Lett., 33, L11105,
4. Dennerl K. et al., “ First observation of Mars with XMM-Newton - High
resolution X-ray spectroscopy with RGS”, A&A, 451, 709 (2006).
5. Pepino, R., V. Kharchenko, A. Dalgarno, and R. Lallement, “ Spectra
of the X-Ray Emission Induced in the Interaction between the Solar Wind
and the Heliospheric Gas”, ApJ, 617, 1347 (2004).
6. Wargelin, B. J. , M. Markevitch, A. Dalgarno, V. Kharchenko et al., “
Chandra observations of the "dark'' Moon and geocoronal solar wind
charge transfer”, ApJ, 607, 596 (2004)
7 . Kharchenko, V., M. Rigazio, A. Dalgarno, and V. Krasnopolsky, “
Charge abundances of the solar wind ions inferred from Cometary X-ray
ApJ Lett., 585 , L73 (2003)
8. Krasnopolsky, V. A., D. J. Christian, V. Kharchenko, A. Dalgarno, S.
J. Wolk, C. M. Lisse, and S. A. Stern, 2002, Icarus, “X-Ray Emission
from Comet McNaught-Hartley (C/1999 T1)”, 160 , 437 (2002)
9. Rigazio, M., V. Kharchenko, and A. Dalgarno, 2002, " X-ray emission
spectra induced by hydrogenic ions in charge transfer collisions", Phys.
Rev. A, 66, 64701 (2002)
10. Kharchenko V. and A. Dalgarno, “ Variability of cometary X-ray
emission induced by solar wind ions”, ApJ Lett., 554, L99 (2001)
11. Kharchenko V. and A. Dalgarno, “ Spectra of cometary X-rays induced
by solar wind ions}, J. Geophys. Res., 105, 18351 (2000)
V. Kharchenko and A. Dalgarno
Brightness distribution of the charge-exchange X-ray emission induced by
the solar wind,
interacting with the interstellar neutral gas.