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Опубликовано
2009-07-09
Опубликовано на SciPeople2014-05-07 07:26:25
ЖурналJournal of Atmospheric and Solar-Terrestrial Physics
On the modulation of intensity of Alfve´n resonances before earthquakes: Observations and model
Аннотация
Modulation of magnetic components of ULF Alfve´n wave (f=0.02–2 Hz), which is incident from the
magnetosphere to the Earth’s surface, is considered. This modulation is due to variations of electron
and ion concentrations within the ionosphere F-layer caused by acoustic-gravity waves or internal
gravity waves of ULF (0.0005–0.02 Hz) range. The maximum modulation of the magnetic field at
the Earth’s surface takes place when maximum variations of the electron concentration are observed at
altitudes 225–275 km. The modulation is more essential when the inclination angle of the geomagnetic
field is Z501. The 20% modulation of the electron concentration results in the magnetic field
modulation at the Earth’s surface of 30–40%. At the frequencies f1 Hz there exists the resonant
modulation when in the narrow (0.1 Hz) frequency range the modulation increases sharply. The
results can explain the ground-based observations of generation of the seismo-related ULF magnetic
perturbations.