Energetic Neutral Hydrogen Atoms Distribution in the Heliosphere: Observations with SOHO/CELIAS

M. Hilchenbach, K.C.Hsieh, H. Grünwaldt, F.M. Ipavich, F. Gliem, P. Bochsler, B. Klecker, D. Hovestadt, and the CELIAS TEAM

Paper presented: 31st ESLAB Symposium, 22-25 September 1997, ESTEC, Noordwijk, The Netherlands

The time-of-flight mass spectrometer CELIAS/HSTOF on SOHO has the capability of detecting energetic neutral hydrogen atoms (ENHA) in the energy range between 60 and 80 keV. The source of energetic neutral atoms are singly charged energetic ions, neutralised i.e. by charge exchange. Neutrals are unaffected by magnetic and electric fields, thus moving on ballistic trajectories and therefore can be detected across long distances. We shall report on the observed ENHA apex-antiapex heliosheric distribution derived from the data collected during th quiet sun cycle since the SOHO launch. The implications of this observations on the existing models of ENHA production in the heliosphere will be discussed, i.e. the ENHA distribution resulting from the anomalous cosmic ray (ACR) protons transcharging on the local interstellar medium neutral atoms.

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Last Update: May 29, 1997, Peter Wurz