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| Titel |
Solar zenith angle dependencies of F1-layer, NmF2 negative disturbance, and G-condition occurrence probabilities |
| VerfasserIn |
V. V. Lobzin, A. V. Pavlov |
| 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. 11 ; Nr. 20, no. 11, S.1821-1836 |
| Datensatznummer |
250014496
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| Publikation (Nr.) |
 copernicus.org/angeo-20-1821-2002.pdf |
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| Zusammenfassung |
Experimental data
acquired by the Ionospheric Digital Database of the National Geophysical Data
Center, Boulder, Colorado, from 1957 to 1990, are used to study the dependence
of the G condition, F1-layer, and NmF2 negative disturbance occurrence
probabilities on the solar zenith angle during summer, winter, spring, and
autumn months in latitude range 1 (between - 10° and + 10° of the geomagnetic
latitude, 8), in latitude range 2 (10° < |F| <
30°), in latitude range 3 (30° < |j| <
45°, 30° < |F| < 45°), in latitude
range 4 (45° < |j| < 60°, 45° < |F|
< 60°), and in latitude range 5 (60° < |F|
< 90°), where j is the geographic
latitude. Our calculations show that the G condition is more likely to occur
during the first half of a day than during the second half of a day, at all
latitudes during all seasons for the same value of the solar zenith angle. The
F1-layer occurrence probability is larger in the first half of a day in
comparison with that in the second half of a day for the same value of the
solar zenith angle in latitude range 1 for all seasons, while the F1-layer
occurrence probability is approximately the same for the same solar zenith
angle before and after noon in latitude ranges 4 and 5. The F1-layer and G
condition are more commonly formed near midday than close to post sunrise or
pre-sunset. The chance that the day-time F1-layer and G condition will be
formed is greater in summer than in winter at the given solar zenith angle in
latitude ranges 2–5, while the F1-layer occurrence probability is greater in
winter than in summer for any solar zenith angle in latitude range 1. The
calculated occurrence probability of the NmF2 weak negative disturbances
reaches its maximum and minimum values during daytime and night-time
conditions, respectively, and the average night-time value of this probability
is less than that by day for all seasons in all studied latitude regions. It is
shown that the NmF2 normal, strong, and very strong negative
disturbances are more frequent on average at night than by day in latitude
ranges 1 and 2 for all seasons, reaching their maximum and minimum occurrence
probability values at night and by day, respectively. This conclusion is also
correct for all other studied latitude regions during winter months, except for
the NmF2 normal and strong negative disturbances in latitude range 5. A
difference in the dependence of the strong and very strong NmF2 negative
disturbance percentage occurrences on the solar zenith angle is found between
latitude ranges 1 and 2. Our results provide evidence that the daytime
dependence of the G condition occurrence probability on the solar zenith angle
is determined mainly by the dependence of the F1-layer occurrence probability
on the solar zenith angle in the studied latitude regions for winter months, in
latitude range 2 for all seasons, and in latitude ranges 4 and 5 for spring,
summer, and autumn months. The solar zenith angle trend in the probability of
the G condition occurrence in latitude range 3 arises in the main from the
solar zenith angle trend in the F1-layer occurrence probability. The solar
zenith angle trend in the probabilities of strong and very strong NmF2
negative disturbances counteracts the identified solar zenith angle trend in
the probability of the G condition occurrence.
Key words. Ionosphere (ionospheric disturbances,
ionosphere-atmosphere interactions, ion chemistry and composition) |
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