DIURNAL TIDE IN THE ANTARCTIC AND ARCTIC MESOSPHERE LOWER THERMOSPHERE REGIONS

The behaviour of the diurnal tide at 95 km over various years between 1965 and 1986 is studied using radar data from Heiss island (81 degrees N), Mawson (67 degrees S), Molodezhnaya (68 degrees S) and Scott Base (78 degrees S). The observations are also compared with the model results of FORBES and HAGAN [(1988) Planet, Space Sci. 36, 579] for the same latitudes. There are substantial fluctuations in amplitude and phase at all stations, particularly in winter. Phase fluctuations can be as large as a uniform random distribution over the 24-h cycle. In summer the phases of the meridional components are well defined and suggest the presence of a dominant symmetric mode. The meridional amplitudes are larger in summer whereas the zonal components have a greater variation and show no significant variation with season.