PHASES AND AMPLITUDES OF TIDS IN THE HIGH-LATITUDE F-REGION OBSERVED BY EISCAT

Travelling Ionospheric Disturbances (TIDs) are the ionospheric respons e to gravity waves passing through the neutral atmosphere. They can be measured simultaneously as wavelike perturbations of the ionospheric electron density (N-e), field-aligned ion velocity (V-i), and ion and electron temperature (T-i and T-e) by the EISCAT radar at Tromso. In o rder to derive the average amplitude and phase relationships between N -e, V-i, T-i and T-e have selected 45 TIDs with periods in the range 3 0-150 min from EISCAT data of a quiet daytime F-region from November 1 987 to December 1991. It is shown that there exist characteristic phas e differences between the TID parameters which can be used to identify gravity waves in incoherent scatter data. Furthermore, we present hei ght, profiles of the average phases and amplitudes of the various TID parameters. Finally, the spectral behaviour of the TID amplitudes is s tudied using the average power spectra of N-e, V-i, T-i and T-e. We co nclude that the use of the incoherent scatter information of all TID p arameters allows a sure identification of gravity waves in the thermos phere.