F-region irregularity drifts deduced from the scintillation measurements by two closely-spaced antennas

By using the ETS-II VHF signal, the one-dimensional irregularity drifts in the summer nighttime F-region have been derived for both the north-south and east-west directions, over an observational period of 27 days. The results suggest that the irregularity sizes are much larger than the antenna spacings because the cross-correlation peaks are generally high and the peak widths are much larger than the time lags. It is found that the south-westward drifts were predominant during 2100-0200 LT, although the drift direction changed with the lapse of time. The averaged one-dimensional drift velocities obtained during this period were 72.1 m/s to the south and 70.3 m/s to the west. The magnitudes and directions of the drift velocities, especially a westward drift tendency, obtained by these measurements agree qualitatively with previous observations.