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| Titel |
Magnetic observatories: biases over CHAMP satellite mission |
| VerfasserIn |
G. Verbanac, M. Mandea, M. Bandić, S. Subašić |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 6, no. 2 ; Nr. 6, no. 2 (2015-06-26), S.775-781 |
| Datensatznummer |
250115465
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| Publikation (Nr.) |
 copernicus.org/se-6-775-2015.pdf |
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| Zusammenfassung |
| Taking advantage of 9 years of the CHAMP (CHAllenging Minisatellite Payload) satellite mission
(June 2000–August 2009), we investigate the temporal evolution of the
observatory monthly magnetic biases. To determine these biases we compute X
(northward), Y (eastward) and Z (vertically downward) monthly means from
42 observatory 1 min values or hourly values, and compare them to
synthetic monthly means obtained from a G field model (Lesur et al., 2015).
Afterwards, the average of biases at all observatories over 9 years is
calculated and analyzed. Both the long-term trends and short-period
variations (hereafter ε variations) around these
averages are then investigated. The simple oscillatory pattern of
ε, found at all observatories and in each component over
the entire considered period, indicates that the crustal field has not
changed. A comparison with both MAGSAT and Ørsted biases given for epochs
1979.92 and 1999.92 which are based on 2 single months (November and
December) of MAGSAT and Ørsted satellite data, respectively, further shows
that the crustal field has probably remained constant over last 3
decades. The long-trend seen in ε reflects the changes
within the solar cycle 23. The short period variations observed in the
ε time series are related to the external field. The
amplitudes of these variations are found to be in phase with solar cycle
periods, being remarkably larger over 2000–2005 than 2006–2009. Furthermore,
clear semi-annual variations are observed in ε, with
larger extremes appearing mostly around October and November, and around May
and June of each year in X, and vice versa in Y and Z. A common
external field pattern is found for the European monthly biases. The
dependence of the bias monthly variations on geomagnetic latitudes is not
found for non-European observatories. The results from this study represent
a base to further exploit the magnetic biases computed for observatories and
repeat station locations together by using data from the new satellite
mission Swarm. |
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