摘要：High frequency Doppler observations of the ionosphere began in August of 1957 in Kyoto. The number of the observation points worldwide were about 40 in 1980 and are about 20 at present. By this method the movement of the ionosphere reflection height and electron density below the height can be observed. Such variations are occurred by a wide variety of sources.
关键词：CODATA;; Ionosphere; Electron Density; Time Variation; Magnetic Storm; Earthquake
