Convective diffusion in the equatorial F region

Abstract This paper discusses the convective diffusion which Johnson and Hulburt showed could take place across the geomagnetic field in the F region near the equator. It is shown that the convective diffusion will increase any irregularities which may be present. The usual formula for the conductivity is found to be inappropriate when diffusion is involved. The convective motion is regarded as that of a gravity-driven dynamo and its speed is controlled by the current flowing along the lines of force into lower levels of the ionosphere. The speed is found to be inversely proportional to the cast-west scale of the irregularities, and for a scale of 100 metres may be a few metres/sec.