The presence of a ledge of ionization between the E and F2 layer maximum electron density, either with a distinct critical frequency (f0F1) or in the form of an inflection point, is found to be a persistent feature of the equatorial ionosphere from 0700 to 1800 LT at low solar activity. The electron density NF1, and the height hF1, at the position of minimum gradient in ionospheric profiles were investigated for Ouagadougou, Burkina Faso, an equatorial station. NF1 was found to exhibit a clear diurnal variation, which depends on solar zenith angle (x). The cos(x) power was found to be 0.34. An obvious seasonal variation in NF1 was not found. The height hF1 shows neither a diurnal nor seasonal dependence, and has an average value of (166¿6) km. NF1 and hF1 were compared at 1000, 1200 and 1400 LT in the months of January and July, for Ouagadougou and Ibadan, Nigeria, another equatorial station. The comparison shows that there is no significant difference in hF1 for both stations, but some differences were found in NF1.¿ 1997 American Geophysical Union