Pre-seismic irregular ionosphere and its effect on the Total Electron Content and Scintillations as observed from Kolkata during Nepal Earthquake on 12 May 2015

The pre-seismic anomalous condition in the ionosphere and the electromagnetic perturbations due to seismic activity have been known for a long time. Variations in ionospheric parameters above seismically active regions are one of most actual reasons of these perturbations. It is well established through many research papers that radon is considered as earthquake precursor. Anomalous soil radon (radon 222) fluctuations as a signal of Nepal earthquake in 12 May 2015 have been reported by Argha Deb and his group [1]. According to them, radon anomalies on 29April 2015 were mainly observed 13 days prior to the M7.3 earthquake on 12 May in Kolkata, Jadavpur University. With reference to that our study has been made on total electron content (TEC) and carrier level fluctuations of GNSS satellite data taken with Septentrio receiver at the Institute of Radio Physics and Electronics, Calcutta University, Kolkata during April-May 2015. It is found that there is a good correspondence between the Radon emission, abnormal change in total electron content and some intense scintillation behaviour in the signal level of GNSS satellites.