Aspects of the Present Heliospheric Research

  • H. J. Fahr
Conference paper
Part of the Reviews in Modern Astronomy book series (MOD.ASTRONOMY, volume 4)


First of all the question is raised here why the sun at all is surrounded by a circumsolar heliosphere, instead by a Strömgren sphere configuration. The fact that counts most in this context is the evident peculiar motion of the sun relative to the ambient interstellar medium. An interesting puzzle thus is how the inner heliospheric plasma properties reflect this fact. Here we briefly will follow the lines by which the interstellar medium influences the heliospheric plasma.

Neutrals and ions are strongly coupled in interstellar/interplanetary space by mutual charge exchange reactions. Over distance scales of the order of charge exchange mean free paths the thermodynamic state of neutral and ionized media thereby is mutually communicated. In the following we study the penetration of neutral interstellar atoms through the perturbed plasma region ahead of the solar system into the inner regions of the heliosphere where their presence has been proven by their typical resonance glows. First we give the main outlines of the theory connected with this problem and then address in detail the question of the neutral hydrogen and oxygen presence in the heliosphere. The conclusion is reached that for interstellar ion densities of 10−2 cm −3 or greater neutral LISM hydrogen or oxygen will be depleted at least by factors of 0.5 or 0.1, respectively. The problem still stands whether or not the anomalous cosmic ray components showing up as He+,O +,Ne +,N +-ions of about 10 MeV/Nucleon in the inner heliosphere can be ascribed to LISM neutrals entering the heliosphere and becoming ionized and reenergized there.

We follow these claims for the origin of the anomalous cosmic rays and discuss in this context quantitative results connected with theoretical predictions for the LISM penetration into the heliosphere. We reach the conclusion that the ratios between the production rates for He+,O +,Ne +,N +-ions cannot be brought into accordance with those values needed to explain the anomalous cosmic ray observations, unless element-specific reenergization efficiencies are admitted.


Solar Wind Charge Exchange Outer Heliosphere Local InterStellar Medium Resonant Charge Exchange 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1991

Authors and Affiliations

  • H. J. Fahr
    • 1
  1. 1.Institut für Astrophysik und Extraterrestrische ForschungUniversität BonnBonn 1Fed. Rep. of Germany

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