Anomalous cosmic rays and the generation of energetic neutrals in the region beyond the termination shock

¹ Space Research Centre, Polish Academy of Sciences, Bartycka 18A, 00-716 Warsaw, Poland
² Institut für Theoretische Physik IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
³ Service d'Aéronomie du CNRS, BP 3, Verrières le Buisson, 91371, France
⁴ Max-Planck-Institut für Aeronomie, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
⁵ Physics Department, University of Arizona, Tucson, AZ 85721, USA
⁶ Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
⁷ Institut für Astrophysik und Extraterrestrische Forschung, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Corresponding author: A. Czechowski, ace@cbk.waw.pl

Received: 22 June 2000
Accepted: 19 December 2000

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 some 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.