An expression is derived for the anomalous diffusion coefficient associated with collisional interchange turbulence in the equatorial F region ionosphere. Waves with &ohgr;≪&ngr;in≪&OHgr;i are considered. The calculation makes use of the renormalization group method, following closely that of Kichatinov [1985>. The calculation is applied to the problem of plasma waves in the equatorial F region ionosphere generated by the ionospheric interchange instability. Approximations appropriate for the geometry of that problem are incorporated into the calculation. Using a model spectrum of the irregularities based on in situ satellite observations, we calculate that the anomalous diffusion seen by large-scale plasma waves can be 5 orders of magnitude larger than the ambipolar diffusion coefficient. ¿ 1998 American Geophysical Union