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| Titel |
Case study on total electron content enhancements at low latitudes during low geomagnetic activities before the storms |
| VerfasserIn |
Libo Liu, Wan Weixing, Man-Lian Zhang, Zhao Biqiang |
| 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 ; 26, no. 4 ; Nr. 26, no. 4 (2008-05-13), S.893-903 |
| Datensatznummer |
250016069
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| Publikation (Nr.) |
 copernicus.org/angeo-26-893-2008.pdf |
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| Zusammenfassung |
| Sometimes the ionospheric total electron content (TEC) is
significantly enhanced during low geomagnetic activities before storms.
In this article, we investigate the characteristics of those interesting TEC
enhancements using regional and global TEC data. We analyzed the low-latitude
TEC enhancement events that occurred around longitude 120° E
on 10 February 2004, 21 January 2004, and 4 March 2001, respectively. The
TEC data are derived from regional Global Positioning System (GPS)
observations in the Asia/Australia sector as well as global ionospheric maps
(GIMs) produced by Jet Propulsion Laboratory (JPL). Strong enhancements
under low geomagnetic activity before the storms are simultaneously
presented at low latitudes in the Asia/Australia sector in regional TEC and
JPL GIMs. These TEC enhancements are shown to be regional events with
longitudinal and latitudinal extent. The regions of TEC enhancements
during these events are confined at narrow longitude ranges around longitude
120° E. The latitudinal belts of maxima of enhancements locate around
the northern and southern equatorial ionization anomaly (EIA) crests, which
are consistent with those low-latitude events presented by Liu et al. (2008). During
the 4 March 2001 event, the total plasma density Ni observed by the Defense
Meteorological Satellite Program (DMSP) spacecraft F13 at 840 km altitude
are of considerably higher values on 4 March than on the previous day in the
TEC enhanced regions. Some TEC enhancement events are possibly due to
contributions from auroral/magnetospheric origins; while there are also
quasi-periodic enhancement events not related to geomagnetic activity and
associated probably with planetary wave type oscillations (e.g. the 6
January 1998 event). Further investigation is warrented to identify/separate
contributions from possible sources. |
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