Earthquake precursors in magnetically conjugated ionosphere regions

It is known that the highly conducting geomagnetic field flux tube and quasitrapped energetic particles provide strong electrodynamic coupling between magnetically conjugated regions in the ionosphere. Such a connection is likely to cause ionospheric disturbances before a pending earthquake not only over the epicentral zone but also in the opposite hemisphere. Data from the INTERCOSMOS-18 and ALOUETTE satellites were analyzed from this point of view. Earthquake precursors in magnetically-conjugated ionosphere regions were found in very low frequency (VLF) emission and F2-peak parameters. F2-precursors appear some days before the earthquake, and manifest themselves as an Appleton-type anomaly if the epicenter of the future earthquake is situated near the magnetic equator. Estimation of the electric field magnitude necessary to generate the observed anomaly was made. It was shown that an electric field of less than one mV/m must be generated in the ionosphere. VLF precursors appearance some hours before the earthquake is localized close to the magnetic shell corresponding to the future earthquake epicenter and have a belt-like structure (longitudealigned for more than some tens thousands kilometers) in both hemispheres. VLF precursors are followed by energetic particle (electrons energy W>40 keV) precipitation.