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| Titel |
Radiation belt data assimilation of a moderate storm event using a magnetic field configuration from the physics-based RAM-SCB model |
| VerfasserIn |
Y. Yu, J. Koller, V. K. Jordanova, S. G. Zaharia, H. C. Godinez |
| 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 ; 32, no. 5 ; Nr. 32, no. 5 (2014-05-06), S.473-483 |
| Datensatznummer |
250121055
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| Publikation (Nr.) |
 copernicus.org/angeo-32-473-2014.pdf |
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| Zusammenfassung |
| Data assimilation using Kalman filters provides an effective way of
understanding both spatial and temporal variations in the outer electron
radiation belt. Data assimilation is the combination of in situ observations
and physical models, using appropriate error statistics to approximate the
uncertainties in both the data and the model. The global magnetic field
configuration is one essential element in determining the adiabatic
invariants for the phase space density (PSD) data used for the radiation belt
data assimilation. The lack of a suitable global magnetic field model with
high accuracy is still a long-lasting problem. This paper employs a
physics-based magnetic field configuration for the first time in a radiation
belt data assimilation study for a moderate storm event on 19 December 2002.
The magnetic field used in our study is the magnetically self-consistent
inner magnetosphere model RAM-SCB, developed at Los Alamos National
Laboratory (LANL). Furthermore, we apply a cubic spline interpolation method
in converting the differential flux measurements within the energy spectrum,
to obtain a more accurate PSD input for the data assimilation than the
commonly used linear interpolation approach. Finally, the assimilation is
done using an ensemble Kalman filter (EnKF), with a localized adaptive
inflation (LAI) technique to appropriately account for model errors in the
assimilation and improve the performance of the Kalman filter. The
assimilative results are compared with results from another assimilation
experiment using the Tsyganenko 2001S (T01S) magnetic field model, to examine
the dependence on a magnetic field model. Results indicate that the data
assimilations using different magnetic field models capture similar features
in the radiation belt dynamics, including the temporal evolution of the
electron PSD during a storm and the location of the PSD peak. The assimilated
solution predicts the energy differential flux to a relatively good degree
when compared with independent LANL-GEO in situ observations. A closer
examination suggests that for the chosen storm event, the assimilation using
the RAM-SCB predicts a better flux at most energy levels during storm
recovery phase but is slightly worse in the storm main phase than the
assimilation using the T01S model. |
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