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| Titel |
Anomalous variations of NmF2 over the Argentine Islands: a statistical study |
| VerfasserIn |
A. V. Pavlov, N. M. Pavlova |
| 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. 4 ; Nr. 27, no. 4 (2009-04-01), S.1363-1375 |
| Datensatznummer |
250016462
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| Publikation (Nr.) |
 copernicus.org/angeo-27-1363-2009.pdf |
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| Zusammenfassung |
| We present a statistical study of variations in the
F2-layer peak electron density, NmF2, and altitude, hmF2, over the Argentine
Islands ionosonde. The critical frequencies, foF2, and, foE, of the F2 and
E-layers, and the propagation factor, M(3000)F2, measured by the ionosonde during
the 1957–1959 and 1962–1995 time periods were used in the statistical
analysis to determine the values of NmF2 and hmF2. The probabilities to observe
maximum and minimum values of NmF2 and hmF2 in a diurnal variation of the
electron density are calculated. Our study shows that the main part of the
maximum diurnal values of NmF2 is observed in a time sector close to midnight
in November, December, January, and February exhibiting the anomalous
diurnal variations of NmF2. Another anomalous feature of the diurnal
variations of NmF2 exhibited during November, December, and January when the
minimum diurnal value of NmF2 is mainly located close to the noon sector.
These anomalous diurnal variations of NmF2 are found to be during both
geomagnetically quiet and disturbed conditions. Anomalous features are not
found in the diurnal variations of hmF2. The statistical study of the NmF2
winter anomaly phenomena over the Argentine Islands ionosonde was carried
out. The variations in a maximum daytime value, R, of a ratio of a
geomagnetically quiet daytime winter NmF2 to a geomagnetically quiet daytime
summer NmF2 taken at a given UT and for approximately the same level of
solar activity were studied. The conditional probability of the occurrence
of R in an interval of R, the most frequent value of R, the mean expected
value of R, and the conditional probability to observe the F2-region winter
anomaly during a daytime period were calculated for low, moderate, and high
solar activity. The calculations show that the mean expected value of R and
the occurrence frequency of the F2-region winter anomaly increase with
increasing solar activity. |
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