@article{oai:nipr.repo.nii.ac.jp:00004050,
 author = {Nozaki, Kenrou and Kikuchi, Takashi},
 journal = {Proceedings of the NIPR Symposium on Upper Atmosphere Physics},
 month = {Feb},
 note = {P(論文), Bottomside ionospheric observation was made with a microcomputer-controlled FM/CW ionosonde at Syowa Station, Antarctica. This ionosonde provides ionograms for the transmitter frequencies from 2 to 16MHz and also sequential data of virtual height (h') at a fixed frequency with a time resolution of 10s. Since the peak power of the FM/CW ionosonde is 20W, continuous observation was possible without disturbing other radio observations and HF radio communications. The continuous observation at a fixed frequency 2.6MHz shows periodic variations in the virtual height and echo intensity with periods of one to several tens of minutes. Periodic variations with a period of several tens of minutes may indicate a propagation or excitation of internal gravity waves during a geomagnetically quiet period, while a variation with a period of 1min could be caused by an oscillatory precipitation of energetic auroral particles.},
 pages = {204--209},
 title = {Preliminary results of the multimode FM/CW ionosonde experiment},
 volume = {1},
 year = {1988}
}