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| Titel |
Ionospheric weather: cloning missed foF2 observations for derivation of variability index |
| VerfasserIn |
T. L. Gulyaeva, I. Stanislwska, M. Tomasik |
| 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 ; 26, no. 2 ; Nr. 26, no. 2 (2008-02-26), S.315-321 |
| Datensatznummer |
250016024
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| Publikation (Nr.) |
 copernicus.org/angeo-26-315-2008.pdf |
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| Zusammenfassung |
| A techique for filling the gaps of the missing F2-layer critical frequency is
proposed and applied for the derivation of the ionospheric weather index,
characterizing the degree of disturbance at each particular station.
A daily-hourly analysis of ionosonde observations of foF2 for 16 stations at
latitude range 37° to 70° N, longitudes of 10° W to 150° E, is
performed during the solar minimum, 2006. Missed ionosonde observations are
reconstructed by cloning data of another station. The process of gap filling
considers hourly values of the F peak density NmF2 (deduced from foF2),
normalized to the respective median, and assumes that this ratio remains the
same for the parent and cloned data. It is shown that the correlation
coefficient between cloned fcF2 and observed foF2 is greater than 0.75 for
the positive and negative ionospheric disturbed days during a year at solar
minimum, independent of the distance between the stations in high and middle
latitudes. The quiet reference is determined as a running daily-hourly median
for 27 days, preceding the day of observation calibrated for a seasonal trend
with ITU-R foF2 predictions. The hourly deviation DNmF2 is defined as the logarithm of ratio of NmF2/NmF2med. A segmented logarithmic scale of the
ionospheric weather index, W, is introduced, so that W=±1 refers to the
quiet state, W=±2 to a moderate disturbance, W=±3 to the ionospheric
storm, and W=±4 to the extreme or anomalous conditions. The catalog of the
ionospheric disturbances for W exceeding ±2 at least during 3
consecutive hours is produced and presented online at the SRC and IZMIRAN web
pages. It is found that the moderate disturbance is a prevailing state of
the ionospheric weather for all stations. The stormy conditions comprise 1
to 20% of the times which occur more frequently at high latitudes, by night, during equinox and winter. |
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