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| Titel |
Statistical characteristics of the total ion density in the topside ionosphere during the period 1996-2004 using empirical orthogonal function (EOF) analysis |
| VerfasserIn |
B. Zhao, W. Wan, L. Liu, X. Yue, S. Venkatraman |
| 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. 12 ; Nr. 23, no. 12 (2005-12-23), S.3615-3631 |
| Datensatznummer |
250015428
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| Publikation (Nr.) |
 copernicus.org/angeo-23-3615-2005.pdf |
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| Zusammenfassung |
| We have applied the empirical orthogonal function (EOF)
analysis to examine the climatology of the total ion density Ni at 840 km
during the period 1996-2004, obtained from the Defense Meteorological
Satellite Program (DMSP) spacecraft. The data set for each of the local
time (09:30 LT and 21:30 LT) is decomposed into a time mean plus the sum of
EOF bases Ei of space, multiplied by time-varying EOF coefficients
Ai. Physical explanations are made on the first three EOFs, which
together can capture more than 95% of the total variance of the original data
set. Results show that the dominant mode that controls the Ni variability is
the solar EUV flux, which is consistent with the results of
Rich et al. (2003). The second EOF, associated with the solar declination, presents an
annual (summer to winter) asymmetry that is caused by the transequatorial
winds. The semiannual variation that appears in the third EOF for the
evening sector is interpreted as both the effects of the equatorial
electric fields and the wind patterns. Both the annual and semiannual variations
are modulated by the solar flux, which has a close relationship with the
O+ composition. The quick convergence of the EOF expansion makes it
very convenient to construct an empirical model for the original data set.
The modeled results show that the accuracy of the prediction depends mainly
on the first principal component which has a close relationship with the
solar EUV flux. |
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