AbstractIncoherent scatter measurements at high latitudes show that in the height range between 100 and 130 km the velocity of the neutral atmosphere shows a prominent sinusoidal component with a 12-hour period. The variation of phase with height for this component is approximately constant from day to day, and corresponds to the predicted variation for the (2,4) mode of the global tide; at greater heights, the variation of phase with height is much slower and corresponds to the (2,2) mode. The amplitude of this semi-diurnal mode as measured at EISCAT shows a deep modulation with a period of about 53 hours, and this is interpreted as the result of a non-linear interaction in the mesosphere between the semi-diurnal tide and the most prominent planetary wave at these latitudes. A diurnal mode is also observed which shows even greater day-to-day variability. There is good qualitative agreement between the measurements made at EISCAT, Chatanika and Søndrestrøm, especially for the semidiurnal component. There is also reasonable agreement with the predictions made using the various models of the lower thermosphere, but the effect of ion on-drag driven by magnetospheric convection is difficult to model in detail, especially at Søndrestrøm. Tidal modes are also observed in the semi-diurnal variation of ion temperature.
Incoherent scatter observations of tides in the lower thermosphere at high latitudes
Advances in Space Research ; 12 , 10 ; 97-106
1992-01-01
10 pages
Article (Journal)
Electronic Resource
English
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