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| Titel |
Occurrence of blanketing Es layer (Esb) over the equatorial region during the peculiar minimum of solar cycle 24 |
| VerfasserIn |
V. Yadav, B. Kakad, C. K. Nayak, G. Surve, K. Emperumel |
| 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 ; 32, no. 5 ; Nr. 32, no. 5 (2014-05-26), S.553-562 |
| Datensatznummer |
250121062
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| Publikation (Nr.) |
 copernicus.org/angeo-32-553-2014.pdf |
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| Zusammenfassung |
| A thin and highly dense sporadic E layer, which can occasionally block the
upper ionospheric layers, is called blanketing sporadic E
(Esb). We present the statistical seasonal local time
occurrence pattern of Esb at equatorial station Tirunelveli
(8.7° N, 77.8° E, dip latitude 0.7° N) during
the extended minimum of solar cycle 24 (2007–2009). In spite of nearly the
same average solar activity during both 2007 and 2009, considerable differences
are noticed in the seasonal occurrence of Esb during this period.
The percentage of Esb occurrence is found to be the highest
during the summer solstice (≥ 50%) for both 2007 and 2009, which is in
general accordance with the earlier studies. The occurrences of
Esb during the vernal equinox (~ 33%) and
January–February (~ 28%) are substantial in 2009 as compared to
those during the same seasons in 2007. We find that, during winter
(January–February), ~ 75% of Esb occurred during or
just after the period of sudden stratospheric warming (SSW). We suggest that
enhanced Esb occurrence during winter (January–February) and the
vernal equinox of 2009 could be associated with SSW-driven changes in the
E region ambient conditions. Furthermore, the close association of
Esb with counter equatorial electrojet (CEEJ) suggested by
earlier studies is re-examined carefully using the scenario of
Esb occurrence on non-CEEJ days. Such an exercise is crucial as
we are unaware whether the physical mechanisms driving Esb and
CEEJ are linked or not. We find that, of all the seasons, the association of
Esb and CEEJ is strongest during winter (November–December). |
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