HF doppler observation between Vostok and Syowa, Antarctica

Continuous short waves transmitted from Vostok Station (78°28′S, 106°48′E) were received at Syowa Station (69°00′S, 39°35′E) on monthly Regular World Days (RWDs). The transmitted frequencies were 14.985MHz from 0700 to 0900UT and 9.18MHz from 1600 to 1800UT. The cusp approached the midpoint of the circuit at the end of the UT morning transmission. Two kinds of Doppler structures were clearly recognized. Narrow band Doppler lines were consistently found during both morning and evening transmissions, whereas wide band Doppler structures dominated only in the morning. The wide band structures appeared and disappeared abruptly and sometimes had two spectrum peaks corresponding to velocities of separated irregularities around the midpoint. The narrow band structures still remained while the wide band structures changed spectrum shapes. Sawtooth-like Doppler structures were found in the narrow band lines in the morning transmissions