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| Titel |
Faraday polarization fluctuations and their dependence on post sunset secondary maximum and amplitude scintillations at Delhi |
| VerfasserIn |
J. K. Gupta, Lakha Singh, R. S. Dabas |
| 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 ; 20, no. 2 ; Nr. 20, no. 2, S.185-190 |
| Datensatznummer |
250014354
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| Publikation (Nr.) |
 copernicus.org/angeo-20-185-2002.pdf |
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| Zusammenfassung |
VHF Faraday rotation (FR)
and amplitude scintillation data recorded simultaneously during May 1978–December
1980 at Delhi (28.63° N, 77.22° E; Dip 42.44° N) is analyzed in order to
study the Faraday polarization fluctuations (FPFs) and their dependence on the
occurrence of post sunset secondary maximum (PSSM) and amplitude
scintillations. It is noted that FPFs are observed only when both PSSM and
scintillations also occur simultaneously. FPFs are observed only during winter
and the equinoctial months of high sunspot years. FPFs events are associated
with intense scintillation activity, which is characterized by sudden onsets
and abrupt endings, and are observed one to three hours after the local sunset.
When FPFs and scintillation data from Delhi is compared with the corresponding
data from a still lower latitude station, Hyderabad (17.35° N, 78.45° E), it
is found that the occurrence of FPFs and scintillations at Delhi is conditional
to their prior occurrence at Hyderabad, which indicates their production by a
plasma bubble and the as-sociated irregularities generated initially over the
magnetic equator. In addition, FPFs and scintillation data for October 1979,
when their occurrence was maximum, is also examined in relation to daytime
(11:00 LT) electrojet strength (EEj) values and evening hour h’F from an
equatorial location, Kodaikanal (10.3° N, 77.5° E). It is interesting to note
that FPFs and scintillations are most likely observed when the EEj was 100 nT
or more and h’F reaches around 500 km. These results show that EEj and
evening hours h’F values over the magnetic equator are important parameters
for predicting FPFs and scintillation activity at locations such as Delhi,
where scintillation activity is much more intense as compared to the equatorial
region due to the enhanced back-ground ionization due to the occurrence of PSSM.
Key words. Ionosphere (equatorial
ionosphere; ionospheric irregularities) – Radio science (ionospheric physics) |
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