Recordings of carrier phase of radio signals from the ATS 6 beacon at Bozeman (Montana), Boulder (Colorado), and Dallas (Texas) have revealed small (<0.1%) sinusoidal fluctuations in total columnar electron content (NT). These oscillations have periods in the range from 30 to 50 s and may continue for several hours near noon on magnetically quiet days. They appear to be associated with micropulsations on the ground and at geostationary heights.