On spread-Es effects in the ionosphere before earthquakes
- 1Institute of Physics of the Earth RAS, Bolshaya Gruzinskaya 10, 123995 Moscow, Russia
- 2High School and Science Programme Brandenburg, Project “Physics of Stellar and Planetary Atmospheres", Astrophysical Institute Potsdam, Solar Observatory Einsteinturm, Telegrafenberg A27, 14473 Potsdam, Germany
- 3Institute of Astrophysics, Bucharskaya str. 22, 734042 Dushanbe, Tadjikistan
Abstract. The spread-Es phenomenon which appears as diffusivity of the traces of sporadic E-layers on the ionogrammes of vertical sounding stations and which reflects the turbulization of the sporadic layers -Es is studied in connection with earthquake preparation processes. Spread-Es data obtained at night every 15 min by the midlatitudinal vertical sounding station of the ionosphere in Dushanbe (φ=38.5° N, λ=68.8° E) are analysed. Groups of earthquakes with different magnitudes and different distances between the epicenter and the sounding station are considered. A statistical analysis of the obtained results is performed. It is shown that during the three nights before an earthquake, spread-Es phenomena are observed more often than during the forth, fifth and sixth nights before the event. This effect is found to depend on both the magnitude of the earthquake and the distance between the epicenter and the sounding station.