Electromagnetic studies of ionospheric and magnetospheric perturbations associated with the earth, atmospheric and astrophysical phenomena

Here, we first analyze data from two GPS stations operating in Tashkent and Kitab and new Very Low Frequency (VLF) radio receiver operating in Tashkent for the possible earthquake ionospheric precursors. We find anomalous Total Electron Content (TEC) precursor signals and significant correlation in time between the TEC anomalies and the occurrence of the earthquake in Tashkent on August 22, 2008, M = 4:4. The obtained results have revealed a fine agreement with the TEC anomalies observed during the strong earthquake in Tashkent and we demonstrate the capabilities of the GPS technique to detect ionospheric perturbations caused by the local earthquakes. TEC decrease during the solar eclipse on August 1, 2008 is also obtained from the data at GPS stations in Tashkent and Kitab. We used tweek radio atmospherics (originating from lightning discharges) to estimate electron densities in the D-layer of ionosphere. The propagation characteristics of tweek atmospherics observed at the Tashkent station have been studied near the mode cut-off frequencies. It is shown that the height of the Earth-Ionosphere Wave Guide (EIWG) varies from 84 km to 91 km and nighttime electron density varies from 25 el=cm³ to 27 el=cm ³. We have also studied VLF amplitude anomalies related to the earthquakes occurring on the path from the VLF transmitters to the Tashkent station. For analyzing narrowband data we have used the Nighttime Fluctuation method paying attention to the data obtained during the local nighttime (18:00 LT- 06:00 LT). The deathlines for rotating as well as oscillating magnetars are obtained for the different modes of oscillations and it is shown that the oscillations increase the region in the P - Ṗ (P is the period) diagram of the magnetars which is allowed for the radio emission.