Mean and periodic components of ionospheric drifts in the D-region at 35°S during 1972

Abstract

Observations of horizontal ionospheric drifts have been made near Adelaide (35°S) using the spaced receiver method as applied to partial reflections from the D-region in the height range 80–100 km. The technique offers a cheap alternative to the radio meteor systems which have previously been used for long term studies of winds at these heights. It has the decided advantage of a time resolution of the order of a few minutes. The 1972 data presented here are among the first partial reflection drifts to be obtained continuously through both day and night. This has permitted 24-h tidal components to be determined. The results are analysed to separate out the mean and periodic components of the motion. On the average, major and roughly equal contributions come from the diurnal oscillation, semi-diurnal oscillation and mean zonal flow. The terdiurnal oscillation and meridional flow emerge as secondary contributors to the overall motion. Significant seasonal variations are apparent in all components. At 85–90 km, the mean zonal component is strongly eastward in winter but westward in early summer. The diurnal tide is dominant in autumn whereas the semidiurnal tide is relatively more important during the spring.