GRAVITY-WAVE PARAMETERS MEASURED WITH EISCAT AND DYNASONDE

Gravity wave activity in the F-region over Tromso has been studied in detail using measurements from the EISCAT incoherent scatter radar, an d the NOAA digital ionospheric sounder (Dynasonde). It has been shown that the field-aligned EISCAT measurement of electron density contains variations which indicate the presence of upward propagating gravity waves with downward progressing wavefronts. The spectral components of these waves have a harmonic relationship, which could suggest a non-l inear generation mechanism. The different frequency components have be en separated using digital filtering, and the observed frequencies and field-aligned wavelengths, together with the background neutral wind (which has been determined from the average field-aligned ion velocity using an appropriate diffusion correction), have been incorporated in to the Hines dispersion equation to obtain the horizontal and vertical wavelengths. The periods and horizontal wavelengths are compared with those measured by the Dynasonde and found to be in good agreement.