Daytime variations of foE connected to earthquakes
- 1Institute of Physics of the Earth of the Russian Academy of Sciences, Bolshaya Gruzinskaya 10, 123995 Moscow, Russia
- 2Institute of Cosmophysical Research and Radio Wave Propagation, Far Eastern Branch of the Russian Academy of Sciences, 684034 Petropavlovsk-Kamchatsky, Russia
- 3Physics Department, University of Bari, 70126 Bari, Italy
- 4Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstr. 9, 64289 Darmstadt, Germany
Abstract. In the present work it is shown that, in accordance with the observations of the vertical sounding station "Tashkent", the critical foE-frequency of the daytime E-layer increases about one day before winter-earthquakes with magnitudes M > 5 and depths of the epicentre of h < 60 km, which appeared at distances of R < 2000 km from the station. The reliability of the result is larger than 99 %. The phenomenon is not observed for summer-earthquakes. It seems to be determined by the atmospheric wind system. Further, the variations of the foE-frequency are compared with possible simultaneous variations of the critical frequency foF2 of the F2-layer. First results show that only very large changes of the ionisation density in the E-layer influence the ionisation density in the F-region. Therefore, no synchronous growth of the foE- and foF2-frequencies 1–2 days before seismic shocks could be observed.