Effects of gravity waves on eclipse time absorption of radio waves.

Ionograms and amplitude measurements at 2.7 MHz taken during the solar eclipse of February 16, 1980, at Gauhati University (India) are discussed. Abnormally low absorption observed during the maximum eclipse effect condition is linked with the formation of distortions or curvatures in the reflecting surface produced by the gravity waves generated during the eclipse. The wave variation pattern of f(0)F2, f(0)F1, etc. seen at this station is seen as supporting the theories of formation of such waves. The amplitudes of undulations of f(0)F1 and f(min) are found to increase when that of f(0)F2 is decreased. In addition to this, the ionization density of the F1 layer is also lowered when that of the F2 layer is increased. The amplitudes of the undulations and ionization densities of the F1 and F2 layers are seen as suggesting the migration of ionization from lower to upper layers and the presence of gravity waves.