Observations of ionospheric disturbances following a 5-kt chemical explosion 1. Persistent oscillation in the lower thermosphere after shock passage

We have observed a 6-min-period oscillation persisting for an hour in the ionospheric E region following a 5-kt chemical explosion on the ground 250 km south of the measurement site. The oscillation's phase velocity in the upper atmosphere is 0.15 km/s at an azimuth 60°W. Our observations are obtained using a time-delayed correlation technique with multistation Doppler sounding of the overhead ionosphere. Some new aspects of the technique are described.