Heights of ionospheric irregularities at a sub-auroral latitude

The heights of ionospheric irregularities were measured at the Sagamore Hill Radio Observatory, 42.6°N, 70.8°W. Beacon signals at 40.01 MHz from Explorer 22 were recorded at spaced receivers during the summer and fall of 1968 and during a short period in the winter of 1969. By using the mean time differences between 1-second samples at each receiver and by using the method of similar fades, the heights of dominant irregularities were found to vary between 130 and 900 km. Scale size (determined from the height measurement and the time between major peaks of the diffraction patterns) increased from 1 km at a height of 200 km to 4 km at a height of 800 km. Two large geomagnetic storms occurred during the test periods. Results were compared with simultaneous measurements of total electron content. The mean height of the irregularity region decreased by 100 km during periods of major depression of total electron content; this decrease suggests that the irregularities are distributed throughout the F region for both quiet and disturbed conditions.