A number of papers have reported on anomalous variation in ionospheric foF2 parameter and/or ionospheric total electron content (ITEC) in the vicinity of earthquake's epicenter few days prior to the earthquake. In this work empirical dependency for the seismo-ionospheric disturbances relating the earthquake magnitude and the epicenter distance are obtained. They have been shown to be similar to those obtained earlier earthquakes. The dependences indicate the process of spreading the disturbance from the epicenter towards periphery during the earthquake preparation process. Large lead times for the precursor occurrence (up to 34 days for M=5.8-5.9) tells about a prolong preparation period. It is shown that different analyses of observed foF2 values lead to different conclusions regarding possible ionospheric precursors. Here we analyze the foF2 and ITEC observations over Greece prior to the three very large earthquakes of
Abstract:The sunspots are widely used to measure the rotational rate of solar surface. We are interested in analysis of the temporal evaluation of the short-term period present in sunspot time series (i.e. sunspot number and area) during the ascending phase of Solar Cycle 24. For the better understanding of variation in solar activity originated at different layers of the solar atmosphere with respect to sunspot cycles, we study the phase relation between sunspot numbers and sunspot areas using cross correlation analysis techniques based on extended wavelet based approaches such as continuous wavelet transform, crosswavelet transform, and wavelet coherence. In this study we found the short-term periodicity "27 days-rotational rate of Sun" for current solar cycle 24 (January 2008-May 2013, which suggested that the Solar Cycle 24 has minimum solar activity. We have also investigated the correlation between both parameters and identify the unusual conditions in space weather.
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