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| Titel |
Secular variation: from observatory monthly means and from global field models |
| VerfasserIn |
Anne Geese, Vincent Lesur, Ingo Wardinski, Mioara Mandea |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034302
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| Zusammenfassung |
| Thanks to the past decade of Geopotential Field Research, including the successful satellites
CHAMP, Ørsted and SAC-C, recent core magnetic field models achieve an unprecedented
accuracy. However, sophisticated models like GRIMM-2 or CHAOS-2 struggle in fitting
some observatory secular variation (SV) estimates. These differences become evident
when the short term SV is considered, i.e. very fast variations of a few months
duration are not reflected by the models. The unmodelled signals can either be of
internal or of external origin. After identifying the observatories for which SV time
series are not properly fitted, we model the differences with the harmonic spline
functions. Those basis functions are located at the selected observatory positions and
permit an exact fit to the data, if required. Additionally, a model based on these
harmonic spline functions can be easily translated in terms of SH, allowing for a direct
comparison with the standard existing models. From the improved spatial and temporal
description of these signals, we expect a better understanding of their underlying causes. |
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