Abstract
Spatial maps of heliospheric and geocoronal X-ray intensities due to the charge exchange of the solar wind with neutrals
Spatial maps of heliospheric and geocoronal X-ray intensities due to the charge exchange of the solar wind with neutrals
I. P. Robertson
Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, USA
T. E. Cravens
Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, USA
X-rays are generated throughout the heliosphere and the terrestrial magnetosheath as a consequence of charge transfer collisions
between heavy solar wind ions and interstellar and geocoronal neutrals, respectively. Simple models of this X-ray emission
have been presented in the past, but results from a more sophisticated model are described in this paper. In particular, to
obtain the densities of interstellar neutrals our X-ray model uses to determine X-ray intensities, we use the
Fahr [1971]
hot model although with recently determined input parameters. The geocoronal X-ray model we use in this paper has also been
improved, as described in a recent paper by
Robertson and Cravens [2003]
. In previous papers we demonstrated that there is significant correlation between the “long-term enhancement” part of the
soft X-ray background measured by the Röntgen Satellite (ROSAT) and the solar wind proton flux. In the current paper we determine
the steady-state X-ray intensities due to the interaction between the solar wind and both interstellar neutrals and the geocoronal
neutrals as a function of look direction and time of year. X-ray intensity maps are shown for both a spherically symmetric
solar wind and for a latitude-dependent solar wind (i.e., fast and slow solar wind regions). In all cases, the X-ray intensity
is highest when the view direction is towards the Sun, but the intensity is also relatively high for view directions intersecting
the gravitational focusing cone of interstellar helium. We also show a heliospheric/geocoronal X-ray intensity map for the
conditions used by
Snowden et al. [1995]
in producing the 1/4 keV channel soft X-ray background map in galactic coordinates. Our preliminary conclusion is that very
roughly 50% of the total background soft X-ray intensity in the galactic plane and 25% at high galactic latitudes can be attributed
to the charge transfer process operating within the solar system, with the remaining emission coming from outside our heliosphere.
Received 31
January
2003;
accepted 11
August
2003;
published 17
October
2003.
Citation: Robertson, I. P., and T. E. Cravens
(2003),
Spatial maps of heliospheric and geocoronal X-ray intensities due to the charge exchange of the solar wind with neutrals,
J. Geophys. Res.,
108(A10),
8031,
doi:10.1029/2003JA009873.