Removal of solar radiation effect based on nonlinear data processing technique for Seismo-Ionospheric Anomaly before few earthquakes

摘要

The study of ionospheric precursorsof earthquakehas gained interest among many researchers, specially the precursor obtained in terms of anomalous variation in total electron content (TEC). If earthquake occurs during a period of moderate to high solar activity, the TEC derived using global positioning system (GPS) measurements requires the elimination of solar effect so as to identify the precursory signature. This paperincludes multi-resolution time series technique to remove the nonlinear effect from solar radiation on GPS-based TEC. The technique is based on wavelet transform applicable to RINEX TEC data. This technique is used to remove nonlinear background solar effect from TEC prior to four different earthquakes (M 6.0). Further in order to evaluate the extracted TEC, we obtain the correlation between the decomposed TEC A6 and measured solar index (F10.7) and extreme ultraviolet (EUV). A good correlation is obtained between decomposed TEC A6 and EUV for all the cases. This suggests that this technique is useful in removal of background solar effect for identifying earthquake precursor in TEC.