Periodic analyses of H and Z are presented, and it is verified that the annual and quasi-biennial waves in H and Z can be caused by dynamo effects. Such waves need not appear in the spectr of geomagnetic activity indexes, such as Ap. An estimate of the annual wave in H produced by the annual waves in ionospheric wind speed yields a reasonable amplitude. It is suggested that the quasi-biennial oscillation in H and Z ia also caused by ionospheric winds.