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| Titel |
Day-time dependence of foF2 variations connected with earthquakes |
| VerfasserIn |
Elena Liperovskaya, Claudia-Veronika Meister, Dieter H. H. Hoffmann, Alexandra Silina |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104800
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| Publikation (Nr.) |
 EGU/EGU2015-5626.pdf |
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| Zusammenfassung |
| In the present work, the day-time variation of the characteristic frequency foF2
of the ionosphere is studied with regard to changes of the seismic activity of the
Earth. Used are observations of the vertical ionospheric sounding station “Tokyo”
registered in the years 1957-1990. In the analysis, data of the ionopsheric parameter
δF = (foF2 - median(foF2))/median(foF2) are used. Smoothed median data, measured
between seven days before the earthquakes and seven days after the seismic shocks, i.e.Âin
the time interval (-7,7), are taken into account. The choice of the parameter δF allows to
compare time intervals of different seasons. Further, the day-time behavior of the
δF -changes on the days (-1,0) are compared with background times. Days with magnetic
disturbances described by an index ΣKp > 25 are excluded from the analysis. Within the
frame of the method of superposition of epochs with a reliability of P > 95 %, one may
conclude, that at day-time and before midnight a decrease of the foF2-frequency is observed
for earthquakes with magnitudes M > 5.5 at distances R > RD + 100 km, where
RD = exp(M) designates the dimension of the earthquake preparation region. In the
analysis, some tenths of earthquakes are taken into account. It is shown that the 11-years solar
activity cycle does not influence the obtained effect. Several times, scientists already
mentioned a considerable increase (or decrease) of the foF2-frequency during a time interval
from a few days before strong earthquakes to some days after them. In the present work, it is
statistically shown, that such a tendency exists at distances not farther than 100 km
from the earthquake preparation region, but this phenomenon is not so important
statistically. |
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