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| Titel |
Numerical considerations in simulating the global magnetosphere |
| VerfasserIn |
A. J. Ridley, T. I. Gombosi, I. V. Sokolov, G. Tóth, D. T. Welling |
| 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 ; 28, no. 8 ; Nr. 28, no. 8 (2010-08-27), S.1589-1614 |
| Datensatznummer |
250016874
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| Publikation (Nr.) |
 copernicus.org/angeo-28-1589-2010.pdf |
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| Zusammenfassung |
| Magnetohydrodynamic (MHD) models of the global magnetosphere are very
good research tools for investigating the topology and dynamics of the
near-Earth space environment. While these models have obvious
limitations in regions that are not well described by the MHD
equations, they can typically be used (or are used) to investigate the
majority of magnetosphere. Often, a secondary consideration is
overlooked by researchers when utilizing global models – the effects
of solving the MHD equations on a grid, instead of analytically. Any
discretization unavoidably introduces numerical artifacts that affect
the solution to various degrees. This paper investigates some of the
consequences of the numerical schemes and grids that are used to solve
the MHD equations in the global magnetosphere. Specifically, the
University of Michigan's MHD code is used to investigate the role of
grid resolution, numerical schemes, limiters, inner magnetospheric
density boundary conditions, and the artificial lowering of the speed
of light on the strength of the ionospheric cross polar cap potential
and the build up of the ring current in the inner magnetosphere. It
is concluded that even with a very good solver and the highest
affordable grid resolution, the inner magnetosphere is not grid
converged. Artificially reducing the speed of light reduces the
numerical diffusion that helps to achieve better agreement with data.
It is further concluded that many numerical effects work nonlinearly
to complicate the interpretation of the physics within the
magnetosphere, and so simulation results should be scrutinized very
carefully before a physical interpretation of the results is made.
Our conclusions are not limited to the Michigan MHD code, but apply to
all MHD models due to the limitations of computational resources. |
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