A study of the propertis of internal gravity wave by means of observattions of the 557.7-nm emission line has been carried out. Special emphasis was put on the determination of the kinetic energy density of the waves, which have maxima in winter and in summer, and on the determination of the enhanced diffusion tensor K. Values of Kzz the zz component, important in theoretical models, of the order of 3¿106 cm2 s-1 were obtained, and its seasonal variation exhibits a winter maximum. The enhanced diffusion due to internal gravity waves is highly anisotropic, being the two eigenvalues corresponding to the horizontal degeneration plane of the order of 4¿109 cm2 s-1. The possible relation between K and D region winter anomalous absorption has been also examined.