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| Titel |
Cosmic ray cutoff prediction using magnetic field from global magnetosphere MHD simulations |
| VerfasserIn |
J. M. Weygand, J. Raeder |
| 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 ; 23, no. 4 ; Nr. 23, no. 4 (2005-06-03), S.1441-1453 |
| Datensatznummer |
250015234
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1441-2005.pdf |
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| Zusammenfassung |
| Relativistic particles entering the Earth's magnetosphere, i.e.
cosmic rays and solar energetic
particles, are of prime space weather interest because they
can affect satellite operations, communications, and the safety of astronauts
and airline crews and passengers.
In order to mitigate the hazards that originate from such particles
one needs to predict the cutoff latitudes of such particles as a
function of their energies and the state of the magnetosphere.
We present results from a new particle tracing code
that is used to determine
the cutoff latitudes of 8-15Men-1 alpha particles during the
23/24 April, 1998 geomagnetic storm and the preceding quiet time.
The calculations are
based on four different geomagnetic field models and compared
with SAMPEX observations of alpha particles in the same energy range.
The geomagnetic field models under consideration are: (i) the
International Geomagnetic Reference Field (IGRF) model,
(ii) the Tsyganenko "89" model (T89c), (iii) the Tsyganenko "96" model (T96),
and (iv) a global magnetohydrodynamic (MHD) model of Earth's magnetosphere.
Examining 11 SAMPEX cutoff latitude observations
we find that the differences between the observed and the
predicted cutoff latitudes are
2.3° ± 2.0° (mean) and 7.9° (maximum difference) for the IGRF model;
3.9° ± 2.4° (mean) and 6.9° (maximum difference) for the T89c model;
4.0° ± 1.4° (mean) and 5.5° (maximum difference) for the T96 model;
and
2.5° ± 1.7° (mean) and 7.0° (maximum difference) for the MHD model.
All models generally predict cutoff latitudes equatorward of
the SAMPEX observations.
The MHD model results also
show steeper cutoff energy gradients with latitude compared to
the empirical models and more structure
in the cutoff energy versus latitude function, presumably due to the
presence of boundary layers in the MHD model. |
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