Some current developments in radio systems for sounding ionospheric structure and motions

Two new developments in radio pulse sounding of the ionosphere are described with emphasis on some advantages available from modern digital techniques. The current stage of development of a digital ionosonde (dynasonde) is illustrated, showing the effectiveness of a simple logical process for distinguishing echoes from noise. Another digital radio-sounding system, including instrumentation (the kinesonde) and data analysis methods, has been developed to provide a statistical description of ionospheric motion and microstructure. From digital recordings of the time variation of complex echo amplitude at four antennas and six frequencies, a multidimensional correlation (correloid) analysis provides a profile of the three-dimensional mean motion, random (characteristic) velocity, shape, size, anisotropy, and lifetime of irregularities in the radio echo pattern; these irregularities can be related to their counterparts in the ionosphere.