Seismo-ionospheric Perturbation as Determined from TEC Monitoring at Agra

摘要

Employing a GPS Ionospheric Scintillation and TEC Monitor (GISTM) System (Model GSV4004B) themonitoring of Total Electron Content (TEC) has been started at Bichpuri, Agra (Geographic Lat.27.2°N,Long. 78°E) since 24 June, 2006 on a routine basis. The slant TEC obtained from the output of thereceiver is converted into Vertical TEC (VTEC) and Ionospheric Pierce Point (IPP) is determined usingthe azimuth and elevation angles of the satellites and suitably developed formulae. The initial data forthe period of six months from August, 2006 to January, 2007 are analysed and temporal variation ofVTEC are studied for the ionospheric region over Agra. The results show that the mean TEC variesfrom a minimum at 0500 hrs LT to a peak value at about 1400 hrs LT and then decreases such that itreduces to a little over minimum value at 2200 hrs LT. Abnormal variation from this regular feature isseen between 04 January to 10 January 2007 during the case study of an earthquake occurred on 08January 2007 in Afganistan region (Latitude 39.81, Longitude 70.33). It is found that the values ofVTEC decreases about 04days and 01day before the main shock and enhanced after the occurrenceof the earthquake. Since there was no magnetic storm or solar flare during these periods, this irregularvariation may be due to the earthquake of 08 January, 2007.