Authors: Czechowski A, Fichtner H, Grzedzielski S, Hilchenbach M, Hsieh KC, Jokipii JR,
Kausch T, Koda J, Shaw A
Reference: ASTRONOMY AND ASTROPHYSICS 368 (2): 622-634 MAR 2001
Abstract:
Some characteristics of the neutral hydrogen flux of 55-80 keV detected by CELIAS/HSTOF on board SOHO
(in particular. the intensity peaks during the periods when the instrument was directed towards the
anti-apex of the local interstellar medium) suggest that the observed atoms may be created in the
distant heliosphere, beyond the termination shock, from the anomalous cosmic ray protons which become
neutralized by charge-exchange with the background gas. The theoretical models on which this conclusion
was first based were very simple and missed st,me important features. Here we report about the first
study of transport of low energy anomalous cosmic rays beyond the solar-wind termination shock
employing a model of the heliosphere treating self-consistently the flows of plasma and neutral atoms
and including the pressure of cosmic rays. The energetic neutral-atom (ENA) flux created by
charge-exchange is calculated and compared with the observations of CELIAS/HSTOF. The viability of
using ENAs as a means of imaging the structure of the termination shock, the distant heliosphere and
the very local interstellar medium is discussed. We also include some results which may be interesting
in connection to possible observations by INCA/Cassini and HENA/IMAGE.
Keywords: solar wind, interstellar medium, cosmic rays