摘要：Low frequency (10～100Hz) electron density irregularities were observed in the height range of 90 to 120km in the polar ionosphere by Langmuir probes on board sounding rockets launched at Syowa Station in 1972-1973. Preliminary analysis shows that the irregularities have relative amplitudes with respect to the ambient average electron density of a few to 10% and that the irregularity region seems to be closely related with optical aurora.
