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| Titel |
E layer dominated ionosphere observed by EISCAT/ESR radars during solar minimum |
| VerfasserIn |
Hongtao Cai, Fei Li, Ge Shen, Weijia Zhan, Kangjun Zhou, Ian Willian McCrea, Shuying Ma |
| 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. 10 ; Nr. 32, no. 10 (2014-10-10), S.1223-1231 |
| Datensatznummer |
250121117
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| Publikation (Nr.) |
 copernicus.org/angeo-32-1223-2014.pdf |
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| Zusammenfassung |
| According to the study by Mayer and Jakowski (2009), periods of E layer
dominated ionosphere (ELDI) are defined as being characterized by vertical
electron density profiles having a maximum density at E layer altitudes. In
this paper, characteristics of ELDI intervals have been investigated,
focusing on their temporal variations, using field-aligned measurements from
the EISCAT and ESR radars during the interval 2009–2011. ELDI events were
identified using simple but reasonable criteria, in which a minimal duration
was required to exclude possible "fake" events induced by random errors in
measurements. It was found that ELDIs were observed more often in winter and
earlier spring than other seasons, especially in the auroral zone. The
occurrence of ELDI intervals peaks around geomagnetic midnight at auroral
latitudes, while it reaches a maximum around geomagnetic local noon at the
latitude of the ESR. Our results imply that ELDI intervals appear to be a
sporadic rather than a regular phenomenon, in disagreement with previous
results inferred from radio occultation measurements. The discrepancy between
the typical durations of ELDI events observed by the two radars is
remarkable, being 30 min on average at Tromsø but about a half of this at
Svalbard. During intervals of ELDI, the mean thicknesses of the E layer are
quite close at the two sites, as are the values of HmE and the
ratio of NmE / NmF2. Case studies confirm
that either extra E layer ionization or F layer density depletion alone could
lead to the presence of ELDIs. Based on a careful check on ELDI intervals of
various types, however, we suggest that both of them play a critical role in
ELDI formation. |
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