Preseismic Ionospheric Electric Field Irregularities Detected by the Double Probes Method

Based on the double probe method, we investigated the ionospheric preseismic electric effects for the strong Chile earthquake of magnitude M = 8.8 that occurred on February 27, 2010, at 06:3414 universal time (UT). To correlate the electrical disturbance to natural geophysical activities in the ionosphere associated with the earthquake, we used a new approach to analyze these disturbances a few days before the event, based on DEMETER spacecraft collected data in the ultra low frequency (ULF) band. The double probes method and the calculated preseismic ionospheric electric field resulting from the potential difference between two electrical probes of ICE (Instrument Champ Electrique) onboard the DEMETER satellite are investigated. Once the effect of the satellite motion is canceled, it is found that the disturbance is caused only by the telluric activity. Moreover, the investigation of the collected data illustrates a clear correlation between preseismic electrical disturbances and ionospheric plasma parameters recorded near the future epicenter. The strongest ionospheric electrical disturbances are located near the future epicenter and close to the geomagnetic conjugate points.