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| Titel |
Effects of the solar wind termination shock and heliosheath on theheliospheric modulation of galactic and anomalous Helium |
| VerfasserIn |
U. W. Langner, M. S. Potgieter |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 22, no. 8 ; Nr. 22, no. 8 (2004-09-07), S.3063-3072 |
| Datensatznummer |
250014987
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| Publikation (Nr.) |
 copernicus.org/angeo-22-3063-2004.pdf |
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| Zusammenfassung |
| The interest in the role of the solar wind termination shock and heliosheath
in cosmic ray modulation studies has increased significantly as the
Voyager 1 and 2 spacecraft approach the estimated position of the solar wind
termination shock. The effect of the solar wind termination shock on
charge-sign dependent modulation, as is experienced by galactic cosmic ray
Helium (He++) and anomalous Helium (He+), is the main topic of this
work, and is complementary to the previous work on protons, anti-protons,
electrons, and positrons. The modulation of galactic and anomalous Helium is
studied with a numerical model including a more fundamental and
comprehensive set of diffusion coefficients, a solar wind termination shock
with diffusive shock acceleration, a heliosheath and particle drifts. The
model allows a comparison of modulation with and without a solar wind
termination shock and is applicable to a number of cosmic ray species during
both magnetic polarity cycles of the Sun. The modulation of Helium, including
an anomalous component, is also done to establish charge-sign dependence at
low energies. We found that the heliosheath is important for cosmic ray
modulation and that its effect on modulation is very similar for protons and
Helium. The local Helium interstellar spectrum may not be known at energies
<~1GeV until a spacecraft actually approaches the heliopause because
of the strong modulation that occurs in the heliosheath, the effect of the
solar wind termination shock and the presence of anomalous Helium. |
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