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Larkina, V.I., Migulin, V.V., Nalivaiko, A.V., Gershenzon, N.I., Gokhberg, M.B., Liperovsky, V.A. and Shalimov, S.L. (1983) Observation of VLF Emissions, Related with Seismic Activity, on the Intercosmos-19 Satellite. Geomagnetism and Aeronomy, 23, 684-687.

has been cited by the following article:

• TITLE: Unusual Change in Critical Frequency of F2 Layer during and Prior to Earthquakes

  AUTHORS: Soujan Ghosh, Sudipta Sasmal, Subrata Kumar Midya, Sandip K. Chakrabarti

  KEYWORDS: Earthquake Early Warning, Wave Propagation, Earthquake Interaction, Forecasting and Prediction, Ionosphere/Atmosphere Interactions, Electrical Properties

  JOURNAL NAME: Open Journal of Earthquake Research, Vol.6 No.4, October 19, 2017

  ABSTRACT: The unusualness in the critical frequency of different layers of earth’s ionosphere is commensurate to be associated with seismic events. We present study of critical frequency of F2 layer (denoted as f0F2) during some major earthquakes in South American region. We use the semi-empirical Barbier’s theorem of air-glow and define a parameter using the critical frequency and virtual height of F2 layer and named it as “F Parameter”. To investigate the variation of this parameter, we consider five large earthquakes in the junction of Nazca plate and South American plate having magnitude greater than M > 6.5 and study the temporal variation of F parameter during these earthquakes. The F Parameter is measured using the ionograms as recorded from the Ionosonde in Jicamarca Radio Observatory (lat. 11.95°S, long 76.87°W) in Chile which lies within the earthquake preparation zones of these five earthquakes. We examine the F Parameter within a span of ±15 days during earthquakes and observed significant change in the evaluated F Parameter in 12 to 3 days prior to the earthquakes. The increment is over +3σ from the normal variation. We also observe significant changes during aftershock events. The solar geomagnetic indices were found to be low which ensures that these anomalies in F Parameter are due to seismic events.