Ionospheric science nowadays contributes to the science and technology of radio communications; the practical use of the ionosphere for communications is still great, and could be improved by further progress in the challenging field of predicting and forecasting. A vast range of electromagnetic emissions and magnetic pulsations originate in the ionosphere. In this book, a method of identifying negative (depletion) and positive (enhancement) phase manifestations of Geomagnetic storms which significantly affects the structure and dynamics of the F-region ionosphere had been examined. The peak monthly geomagnetic storms observed during the rise of solar cycle 23, in the year 2000 were presented. Data from a network of ionosondes stations located within the East Asian latitudinal sector of 40–65°N were employed.The result revealed the action of rapid heating of the polar atmosphere during energy income from the magnetosphere and an eastward electric field as factors to be considered. The analyses should be useful for space weather physicists, climatologists and telecommunication experts.