A new multimode FM/CW ionosonde

A low power FM/CW ionosonde was constructed to investigate the vertical motion of the polar ionosphere. The most suitable pulse length is selected automatically according to the ionospheric layer height. Microcomputer control and data acquisition make it possible to select observation mode easily by changing software. A good deal of effort was made to eliminate interference with other observations and short wave telecommunications and by other emissions on neighboring spots

An Analysis of Pc 1 Magnetic Pulsations Observed by the 17th Japanese Antarctic Research Expedition Wintering Party (d. ULF Waves in the Magnetosphere) (Proceedings of the Second Symposium on Coordinated Observations of the Ionosphere and Magnetosphere in the Polar Regions : Part I)

Diurnal variations of occurrence frequency of Pc 1 pulsations and relationships between Pc 1 events and Kp, Dst and K (at Syowa Station) indices have been studied by using f-t spectra of magnetic pulsations observed at Syowa and Mizuho Stations during one year from January 1976 to January 1977. It is found that the occurrence probability of Pc 1 events does not depend on the magnitude of Kp index, while there is a tendency that the occurrence probability of Pc 1 events increases greatly when the magnitude of Dst index is larger than -80 nT. It is also found that the f-t spectral patterns of Pc 1 events observed at Syowa and Mizuho Stations were generally quite similar to each other. However, several Pc 1 events were observed only at Syowa Station. Furthermore, dynamic polarization patterns of three typical Pc 1 events observed at Syowa Station are given in this paper

VHF/HF radio telecommunications between Syowa Station and Mizuho Station, Antarctica

Radio telecommunication characteristics between Syowa Station and Mizuho Station were studied by using VHF radio wave scattered by ionospheric E-layer irregularity accompanied with aurora. VHF radio wave was propagated in a path greatly different from the great circle course according to the irregularity structure. Total reception time rate was about 5% and VHF radio scatter had good correlation with radar aurora and geomagnetic irregularity at Syowa Station. Geomagnetic irregularity effect on VHF radio scatter was compared with that on HF telecommunication which is easily affected by ionospheric conditions. Complemental relations between HF and VHF telecommunications were discussed

Simultaneous observation of VLF phase and absorption anomalies at Syowa Station, Antarctica in association with magnetospheric substorms

Ionospheric disturbances associated with magnetospheric substorms were detected with VLF (ƒ=10.2 and 13.6kHz) radio wave propagation and a riometer simultaneously at Syowa Station, Antarctica. It is shown that the phase of the OMEGA REUNION signals (10.2 and 13.6kHz, La Reunion) advances significantly in association with geomagnetic bays and ionospheric absorptions. In correspondence to these disturbances, VLF phase anomalies are also observed on the OMEGA ALDRA signal (13.6kHz, Aldra, Norway) as received at Inubo, Japan. The conjugacy of occurrence of the VLF phase anomalies in the northern and southern hemispheres indicates that ionospheric disturbances responsible for VLF phase anomalies are caused by precipitation of energetic electrons from the magnetosphere. Local time characteristics of VLF phase and absorption anomalies are obtained from data recorded during a period from September 1,1980 to January 31,1981. Precipitation of energetic electrons responsible for VLF phase anomalies takes place predominantly in the evening sector peaked around 22 MLT, whereas electron precipitation responsible for absorption anomalies takes place in the morning sector peaked around 0230 and 0730 MLT. The discrepancy in these local time characteristics is due to a difference in height of the ionosphere responsible for the VLF phase anomaly (h30keV and VLF phase anomalies by more energetic electrons with energies>300keV. This conclusion is confirmed qualitatively by observational facts that a significant phase anomaly is observed on the REUNION (10.2kHz) signal which is reflected from the lowermost part of the ionosphere, whereas no corresponding disturbances either on the REUNION (13.6kHz) signal and in ionospheric absorption

ナンキョク ショウワキチ ミズホキチ カン ノ VHF/HF ツウシン

オーロラ発生時の電離層E層不規則構造によるVHF電波散乱通信実験が昭和基地, みずほ基地間で行われた。オーロラ散乱の特性上電波の伝搬通路は大圏コースから大きくはずれる。VHF電波散乱の時間発生率は5%程度で, 昭和基地でのオーロラレーダーのエコー発生, 地磁気じょう乱と良い相関がある。電離層じょう乱により障害を受けやすい両基地間の短波通信と地磁気じょう乱に対する特性を比較して, 短波通信とVHF通信の相補性について論じた。Radio telecommunication characteristics between Syowa Station and Mizuho Station were studied by using VHF radio wave scattered by ionospheric E-layer irregularity accompanied with aurora. VHF radio wave was propagated in a path greatly different from the great circle course according to the irregularity structure. Total reception time rate was about 5% and VHF radio scatter had good correlation with radar aurora and geomagnetic irregularity at Syowa Station. Geomagnetic irregularity effect on VHF radio scatter was compared with that on HF telecommunication which is easily affected by ionospheric conditions. Complemental relations between HF and VHF telecommunications were discussed