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| Titel |
Large enhancements in low latitude total electron content during 15 May 2005 geomagnetic storm in Indian zone |
| VerfasserIn |
N. Dashora, S. Sharma, R. S. Dabas, S. Alex, R. Pandey |
| 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 ; 27, no. 5 ; Nr. 27, no. 5 (2009-05-04), S.1803-1820 |
| Datensatznummer |
250016501
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| Publikation (Nr.) |
 copernicus.org/angeo-27-1803-2009.pdf |
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| Zusammenfassung |
Results pertaining to the response of the equatorial and low
latitude ionosphere to a major geomagnetic storm that occurred on 15 May
2005 are presented. These results are also the first from the Indian zone in
terms of (i) GPS derived total electron content (TEC) variations following
the storm (ii) Local low latitude electrodynamics response to penetration of
high latitude convection electric field (iii) effect of storm induced
traveling atmospheric disturbances (TAD's) on GPS-TEC in equatorial
ionization anomaly (EIA) zone.
Data set comprising of ionospheric TEC obtained from GPS measurements,
ionograms from an EIA zone station, New Delhi (Geog. Lat. 28.42° N,
Geog. Long. 77.21° E), ground based magnetometers in equatorial and low
latitude stations and solar wind data obtained from Advanced Composition
Explorer (ACE) has been used in the present study. GPS receivers located at
Udaipur (Geog. Lat. 24.73° N, Geog. Long. 73.73° E) and Hyderabad
(Geog. Lat. 17.33° N, Geog. Long. 78.47° E) have been used for
wider spatial coverage in the Indian zone. Storm induced features in vertical TEC
(VTEC) have been obtained comparing them with the mean VTEC of quiet days.
Variations in solar wind parameters, as obtained from ACE and in the SYM-H
index, indicate that the storm commenced on 15 May 2005 at 02:39 UT. The main
phase of the storm commenced at 06:00 UT on 15 May with a sudden southward
turning of the Z-component of interplanetary magnetic field (IMF-Bz) and
subsequent decrease in SYM-H index. The dawn-to-dusk convection electric
field of high latitude origin penetrated to low and equatorial latitudes
simultaneously as corroborated by the magnetometer data from the Indian zone.
Subsequent northward turning of the IMF-Bz, and the penetration of the
dusk-to-dawn electric field over the dip equator is also discernible.
Response of the low latitude ionosphere to this storm may be characterized
in terms of (i) enhanced background level of VTEC as compared to the mean
VTEC, (ii) peaks in VTEC and foF2 within two hours of prompt penetration of
electric field and (iii) wave-like modulations in VTEC and sudden enhancement
in hmF2 within 4–5 h in to the storm. These features have been explained
in terms of the modified fountain effect, local low latitude electrodynamic
response to penetration electric field and the TIDs, respectively. The study
reveals a strong positive ionospheric storm in the Indian zone on 15 May
2005. Consequences of such major ionospheric storms on the systems that use
satellite based navigation solutions in low latitude, are also discussed. |
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