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| Titel |
Daytime dependence of disturbances of ionospheric Es-layers connected to earthquakes |
| VerfasserIn |
E. V. Liperovskaya, A. V. Liperovsky, C.-V. Meister, A. S. Silina |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250070772
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| Zusammenfassung |
| In the present work variations of the semi-transparency of the sporadic E-layer of
the ionosphere due to seismic activities are studied. The semi-transparency Q is
determined by the blanketing frequency fbEs and the characteristic frequency foEs,
Q = (foEs - fbEs)-fbEs. At low values of the blanketing frequency fbEs, the critical
frequency foEs does not describe the maximum ionisation density of the Es-layer, as the
critical frequencies of regular ionospheric layers (e.g. foF2) do, but it describes the
occurrence of small-scall (tenths of meters) inhomogeneities of the ionisation density along
the vertical in the layer. The maximum ionisation density of the sporadic layer is
proportional to the square of fbEs. In the case of vertical ionospheric sounding, the
sporadic layer becomes transparent for signals with frequencies larger than fbEs.
Investigations showed that about three days before an earthquake an increase of the
semi-transparency interval is observed during sunset and sunrise. In the present work,
analogous results are found for data of the vertical sounding stations “Tokyo” and
“Petropavlovsk-Kamchatsky”. Using the method of superposition of epoches, more than 50
earthquakes with magnitudes M > 5, depths h < 40 km, and distances between the station
and the epicenter R < 300 km are considered in case of the vertical sounding station
“Tokyo”. More than 20 earthquakes with such parameters were analysed in case of the station
“Petropavlovsk-Kamchatsky”. Days with strong geomagnetic activity were excluded
from the analysis. According to the station “Petropavlovsk-Kamchatsky” about 1-3
days before earthquakes, an increase of Es-spread is observed a few hours before
midnight. This increase is a sign of large-scale inhomogeneities in the sporadic layers. |
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